VALTION MAATALOUSKOETOIM1NNAN JULKAISUJA N:o 131 AGRICULTURAL EXPERIMENT ACTIVITIES OF THE STATE, PUBLICATION N:o 131 ARTIFICIAL HORMONES AND WEED CONTROL IN OIL FLAX CULTIVATIONS JUHANI PAATELA CENTRAL AGRICULTURAL EXPERIMENT STATION, DEPARTMENT OF AGRONOMY, TIKKURILA, FINLAND HELSINKI 1949 VALTION MAATALOUSKOETOIMINNAN JULKAISUJA N:o 131 AGRICULTURAL EXPERIMENT ACTIVITIES OF THE STATE, PUBLICATION N:o 131 ARTIFICIAL HORMONES AND WEED CONTROL IN OIL FLAX CULTIVATIONS JUHANI PAATELA, D. Agr. CENTRAL AGRICULTURAL EXPERIMENT STATION, DEPARTMENT OF AGRONOMY, TIKKURILA, FINLAND HELSINKI 1949 Presented on December 22 1948. Printed on February 5 1949. Helsinki 1949. Valtioneuvoston kirjapaino Preface At Central Agricultural Experiment Station, Department of Agronomy, Tikkurila, Finland, field experiments and investigations with artificial hormones were started in 1946. The investigations continued in summers 1947 and 1948. Principal attention was paid to the effect of these new chemical cornpounds on different weeds and on the possibilities of using them in crop production. Sprays have proved more effective than dusts, but shortage of sprayers has for the present limited the use of artificial hormones in Finland. As' artificial hormones are of great importance in oil flax cultivations, where growth is greatly impeded especially by annual weeds, several experiments have been carried out on oil flax. This book is the first publication of the investigations hitherto carried out at my department, and it is based on the experiments conducted by Dr. J. PAATELA during the growth season. 1948. Tikkurila, January 1949. Otto Valle Contents Page Introduction 7 I. Earlier investigations 9 II. Present investigations 11 A. Methods 11 B. Effect of time of treatment and of amount of effective substance on development of oil flax, on amount of seed and stem yield and on quality of seeci yield 12 Experiments with oil flax treated at different stages of develop- ment 12 Experiments with oil flax treated at similar stage of develop- ment 37 C. Importance of carrier to the effectiveness of artificial hormones with regard to oil flax 40 III. Summary 46 Literature eited 49 Suomenkielinen selostus 51 Introduction Oil flax is a rather small eultivated plant, which does not give much shade, and its development is at first slow. Therefore oil flax cultivations are often heavily infested with weeds. Oil flax cultivation is successful only if the soil is free from weeds, and in rotation oil flax is usually grown after grass land, Potato or root vegetables. At the beginning of the current decade it was discovered in England that some organic acids,fi-indoleacetic acid (plant hormone called earlier heteroauxin), and a-naphtaleneacetic acid with different structure from, the former, applied in solutions at suitable concentrations kill many broad- leaf weeds, but have no injurious effects on the growth of cereals. Soon after this it was observed in England and U. S. A. that some other synthetic coumpounds, such as 2-methy1-4-chloro-, 2,4-dichloro, or 2,4,5-trichloro- phenoxyacetic acid (2M-4K, 2,4-D, and TCP), and their salts and esters, exert similar selective effects. All m,onocotyledonous plants, however, are not resistant, nor are all herbaceous plants sensitive. Oil flax is a her- baceous cultivated plant, which is much more susceptible than cereals but which is more resistant than many of the most sensitive weeds. Therefore it is possible to use artificial hormones 1) for weed control in oil flax cultiva- tions. As the safety m,argin between resistance and injury in oil flax is much smaller than in cereals (wheat, oats, rye, barley), it is very important to -know the roost significant factors affecting the effectiveness of artificial hormones and to use these substances for weed control in oil flax in such a manner that as effeetive control as possible is exerted but the amount or quality of the crop of oil flax is not damaged. Such significant factors are, for instance, treatment at the right stage of developm,ent, right amount of suitable artificial hormones, and climatic and edafic factors. Oil flax is one of the most important oleiferous plants in the world, and therefore weed control in oil flax is a question worth investigating. As it has not hitherto received much attention, the purpose of this study is to contribute to the solution of this important question. In my work I have been assisted by students HELVI MARJANEN and AILI HÄNNINEN, to whom, as well as to Miss ARMI AILAS, who has translated the manuscript into English, I want to express roy thanks in this connection. By artificial hormones or growth regulators we mean in this study synthetic organic compounds, whose effect is similar to that of phytohormones (auxins) but which are not found in plants. I. Earlier in.vestigations The possibilities of using artificial hormones for weed control in.- oil flax have been so far little investigated in Finland. Accorcling to the experim,ents conducted at the Central Agricultural Experiment Station, Department of Agronomy, in summers 1947 and 1948 (so far unpublished) oil flax resisted well e. g. the amounts of 1 kg. of 2M-4K per hectare applied at the rate of 800-1 000 1. per hectare. BREITENSTEIN (4) observed in practice that oil flax was not injured by the English dust Agroxon 1) or by the Finnish dust Hormotox 2) applied at the rate of 200-250 kg. per hectare. This amount was sufficient to kill som.e weeds satisfactorily. This question has received a little more attention in other countries. The experim,ents conducted in Denmark have shown that careful applica- tion of artificial horraones does not reduce the crop of oil flax, and that it is better to use methoxon-compounds than. 2,4-D-compounds (13, 16). RASMITSSEN (14) mentions two experim.ents with 0.5 and 1 % Agroxon 3), applied at the rate of 1 000 1. per hectare. The average yield from un- treated plots, containing 24 % of weeds, was 1 640 kg. of seeds and 3 210 kg. of stems per hectare. In the treated plots the proportion of weeds was only 1.0 and 0.5 % and the increase in yield obtained from these plots was on the average 90 kg. and 10 kg. of seeds and 51 kg. and 58 kg. of stems per hectare. Also in Sweden artificial horraones have been used for weed control in oil flax cultivations. Thus JACOBSON and BJÖRKLUND (8), who report the results of the experiments conducted in Denmark, Sweden, and Norway, recommend for oil flax 5-7 1. of Agroxon or P46 4) per hectare. 2,4-D compounds have proved more dangerous than methoxon compounds and are not suitable for oil flax. The lowest amount (51. per Jaa.) is recom,m,ended by them, for control of Brassica campestris, Sinapis arvensis, Raphav,us raphanistrum„ Thlaspi arvense, and Chenopodium album. If other weeds occur, such as Cirsium arvense, the highest amount (7 1. per Jaa.) is re- commended. Spray applications must never be made later than to plants which have attained the height of 7-10 cm. Spraying at a later stage of development may prove very dangerous, and at a very late stage, when buds appear, spraying m.ust not be given, for it may result in the destruc- Contains 1 % of 2M-4K. ContaiRs 0.5 % of sodium salt of 2,4-D. Contains 10 % of 2M-4K. Prepared in Denmark and contains 10 % of 2M-4K. 2 10 tion of the whole crop. According to them spraying at the right moment has no effect on the oil content of seeds. — ÅBERG, HAGSAND and VÄÄRTNÖU (22) have investigated the effect of artificial hormones on the fibre flax Coneurrent, which is much more sensitive than oil flax. They observed among other things that even such small amounts as 0.5 kg. of Wormosan and 5 1. of Agroxon applied at the rate of 1 000 1. per hectare greatly reduced the amount of both seed and stern crop. The weight per 1 000 seeds seemed to decrease, if the applied amount (4-6 kg. of Wormosan G and 20-40 1. of Agroxon per ha.) of artificial growth regulators significant- ly exceeded the norm,a1 amount, whereas these large amounts bad no effect on the germination of seeds. Spray applications made at different times with sodium, sait "solution of 2,4-D (0.6 and 1.1 kg. per ha.) to plants at different stages of development had no effect on the weight per 1 000 seeds, germination of seeds or on their chemical structure, which, however, was significantly affected by some other compounds. So, for instance, spraying with 0.5-1 % Weedone 2 ) increased the crude protein content of the seeds by 2-3 %, spraying with Agroxon by 0.6-0.3 %, while the oil content decreased corresponclingly by 3.4-5.3 % and by 0.5- 0.9 %. — Weed control in oil flax cultivations by means of artificial hor- mones is most successful, if chiefly methoxon compounds (Agroxon and P 46) are used and applied at the rate of 6-8 1. per hectare, or 60-80 % of the normal amounts given to cereals (22, 23). Experiments with artificial hormones conductedin England (3) show that methoxon compounds may he sprayed on oil flax without danger up to a concentration of 0.2 % of the pure compound at the rate of 100 gallons per acre or about 1 100 1. per hectare. Soclium salt or acid suspension of 2,4-D must not he used in higher concentration than 0.1 %, and ester-oil emulsions are quite unsuitable for oil flax. These maximum concentra- tions can he applied only when the plants have attained the height of 3-4 inches (= 7.5-10 cm.), and before they have attained the height - of 12 inches (= 30 cm.). Spraying applied at right time has no injurious effect on the amount or quality of the seed crop, whereas spray applica- tions made too early or too late may prove dangerous. Dusts, which are less effective than sprays, are recommended by BLACKMAN and HOLLY to he used only where no sprayer is available, water is scarce, or when the most sensitive weeds are eradicated. Dusts must he applied at the rate of a little over 2 lb. of the active compound per acre (= about 2.2 kg. per hectare). Contains 40 % of amino salt of 2,4-D. Contains 9.6 % of 2,4-D. II. Present investigations A..Methods The experiments, which were all .conducted during the growth season 1948 at the Department of Agronomy of the Central Agricultural Experi- ment Station at Tikkurila, were sown in rows with sowing-machine, with 12-15 cm. spaces between the rows. The variety used was the Finnish Tikkurila oil flax (form,er nam,e Ti 0774, weight per 1 000 seeds about 5 gm., period of growing short, on the average 92 days, that of Argentine oil flax being on the average 100 days). The amount sown was approxi- m,ately 100 kg. per ha. The plots, 5.0-6.0 m2, in one experiment 63.4 m2 in size, were placed acc'orcling to the usual row or block m.ethod. Ali experi- ments were carried out with four replicates. Nearly ali experiments (also untreated plots) were as well as possible kept free from, weeds, which were pulled off with hands. Either the Danish Ginge knapsack sprayer or the Swedish TT-Favorit horse-operated sprayer was used to apply the sprays. The solution was applied at the rate of 1 000 1. per ha., or, if the horse-operated sprayer was used, at the rate of 700 1. per ha. Dusts were applied to moistened plants in °alin weather through veil bags. Seed crops were calculated on 98 % purity and 90 % dry basis. The effect of artificial hormones on the quality of crop was examined by deter- mining the weight proportion of sound and membranous seeds in the crop, the weight per 1 000 seeds, and, for a portion of sam,ples, the germination and oil content of seeds, and the refractive number of oil. Classification of seeds was conducted accord.ing to PAATELA (12, p. 16) and the results are averages of 2 samples of 2.5 gm. each. Weights per 1 000 seeds are averages of 4 weighings of 100 seeds, germinations averages -of the results of 4 gerrninating experiments with 50 seeds. Oil content was determined in TWISSELMANN'S apparatus by extracting for 4 hours about 2 1. ether boiling at 3400 through finely ground and dried seed samples. The results, expressed on dry basis, are averages of two determina- tions deviating 0.7 at the most and 0.16 on the average. Dry basis was determined from two seed samples of 2.5 gm. each, which were kept for 12 75 minutes at 120° C. Refractive number was determined with ABBE's refractometer (nD 20° C) from oils obtained with determinations of oil contents. B. Effect of time of treatment and of amount of effective substance on development of oil flax, on amoun.t of seed and stem yield and on quality of seed yield 1. Experiments with oil flax treated at different stages of developnent Experiment 1. — The purpose of the experiment was to find out the effect of methoxon and 2,4-D compounds on oil flax, if applied at different stages of development and as sprays of different concentrations. The plots, 6 m2 in size, were arranged according to row method, number of replicates 4. Treatments: a = untreated, b—d = sprayed with 0.0 5, 0.1, and 0.2 % 2M-4K (= Agroxon), applied at the rate of 1 000 1. per hectare, e—f: sprayed with 0.05 and 0.1 % aqueous solution of soclium salt of 2,4-D. Spray applications were made with the Ginge knapsack sprayer at seven different stages of development. Dates of spray applica- tions, the average height of plants at the time of treatment, and the mean temperature on the day of treatment and during two follo-vving days are given below: Stage of development Date of treatment Average height of plants at time of treatment (cm.) Mean temperature on day of treatment and two following days (0°) I June 3 2.6, cotyledon stage 16.2 II June 9 4.6 18.8 III June 14 7.8 14.o IV June 22 12.5 16.6 V June 26 17.1 18.0 VI July 2 30.o', bud stage 19.s VII July 13 41.5, flowering 16.6 After each treatment observations were made with regard to the effect of artificial hormones, expressed as different degrees of stem curvature. Notes were also made of the period, expressed in days, which passed before the plants recovered, or again attained an upright position. The observa- tions, which are averages of 400 marked individuals in every treatment, are given in Table 1. Figures indicating the average rate of stem curvature on each observation day were obtained by multiplying the proportion of different stem curvature by the degree of curvature (0-4) and divided by 100. A greater degree of stem curvature resulted in higher figures. For methoxon sprays these figures are shown graphically in Fig. 1. 13 Table 1. Effect of artificial hormones on stem curvature and recovery of oil flax plants at stages of development. Rate of stem curvature shown by a scale 0-4: 0 = erect, 1 = about 45° bent, 2 = about 900 bent, 3 = drooping, more than 900 bent, and 4 = lying on the ground or dead ( = cotyle- don stage) or drooping on the ground ( =later stages of development); cp. figures 4-7 on pp. 23-24. Stages 1—VII of development are the same as on page 12. 23.1-4K Sodium salt of 2,4-D Stage of develop- ment and date 1 1/2 1 1 1 2 1 Yz 1 1 Average percentage of degrees of stem curvature 0-4 in 400 plants 0 111 2 3 41 0 11121314 0 1121 3 141 0 1 2 3 4 0 11121 3 1 I 3.6.100 100 100 100 100 5.6. 22 62 16 4 34 56 6 3 22 66 9 (i 7021 3o 4 29 56 11 6.6. 6 82 10 2 1 44 45 10 0 40 50 8 2 2 73 16 9 0 2447 28 1 8.6. 12 82 4 2 5 68 26 0 1 0 51 43 4 2 2 5730 11 2 31 50 15 2 10.6. 54 46 42 41 17 -- -- -- ---- 1Vot eompletely re overe 12.6. 100 20 52 24 2 2 15.6. 83 17 -- -___ -- -- — 16.6. 100 80 12 5 0 3 17.6. 100 II 9.6. 100 100 100 100 100 10.6. 56 39 5 35 52 13 35 4718 81 19 54 46 1 12.6. 83 16 1 51 31 16 2 5 52 36 7 79 21 53 44 3 14.6.100 -- ---- __ __ _ 15.6. 84 16 30 57 12 1 91 9 81 19 16.6. -- -- -- -- 100 -- -- 17.6. 100 68 32 100 21.6. 100 III 14.6. 100 100 100 100 100 15.6. 89 11 71 27 2 24 70 5 1 94 6 94 6 17.6. 100 38 62 4 13 79 4 100 100 19.6. 100 -- -- 23.6. 100 IV 22.6. 100 100 100 100 100 23.6. 5 80 15 1 42 57 0 045 55 92 8 83 17 0 0 25.6.100 81 15 4 5 34 35 26 100 100 27.6. 100 -- -- 30.6. 100 V 26.6. 100 100 100 100 100 27.6. 0 58 38 4 0 688 6 0 0 0 100 100 100 28.6. 6824 8 17 66 17 0 016 84 30.6. 100 62 34 4 0 14 78 8 2.7. 100 19 81 4.7. 100 VI 2.7.100 100 100 1001) 1001 4.7. 0 7 89 4 0 0 32 68 0 0 2 98 0 0 14 86 0 0 0 100 5.7. 1 6 93 0 0 89 11 0 0 7 93 0 0 0 100 0 0 0 100 . 8.7. 6 91 3 0 79 21 0 20 74 6 0 0 31 69 0 0 0 100 10.7. 90 10 68 28 4 5 25 70 6 28 57 9 0 5 73 22 14.7.100 -- -- 18.7. 100 -- -- Not compleely recovere 20.7. 100 VII 13.7. 100 100 100 1002) 1002) 100 100 100 100 100 . 1 and 2 kg of morpholine salt of 2,4-D per ha. y2 and 1 kg. of morpholine salt of 2,4-D per ha. 14 A ve ra ge r at e o f s te m e ur va tu re 0 -4 2 II, 5 cm. PVII, 8 cm. /\. I • \ \ \ ' \ \ • 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 0 2 4 6 8 10 \ \ I \ I \V, 17 cm, \ VI, 30 cm. 2 1 1 0 24 6- - 8 0 2 4 6 8 0 2 4 6 8 10 12 14 16 18 Recovery in days Fig. 1. Effect of methoxon sprayings applied at stages I—VI of development on average Tate of stern curvature and recovery of oil flax cultivations. Broken line = unbroken line = 1, and dotted line = 2 kg. of 2M-4K per ha. , The results given in Table 1 and Figure 1 are somewhat misleading, for ali treated plants, especially those at cotyledon stage, did not recover com,pletely. A number of the plants in the sprayed plots were namely completely killed, as table 2 shows. Each relative number gives the average of 400 plants in different replicate plots marked before the treatment and recounted at the time of harvesting. Table 2. Effect of artificial hormones sprayed at stages 1—VII of develop- ment on relative density of oil flax cultivations. Average density before treat- ment at stage I ---- 156, at stage II=-- 158 plants per row meter. Stages 1—VII of development are the same as on p. 12. Relative density of oli flax cultivations at the time of harvesting Stage of 2M-4K Sodium salt of develop- ment Untreated kg. per ha. 2,4-D kg. per ha. Y2 1 2 1/2 1 I 100 100 97 95 89 87 II 100 100 100 99 100 100 III—VII 100 100 100 100 100 , 100 15 After recovery the effect of artificial hormones sprayed at different . stages of development was chiefly observed as retardation of development. Observations about the height of plants, flowering, and reaching of yellow maturity are given in Tables 3 and 4 and in Figure 2. Heights are averages of about 20 measurements. Table 3. EIteet of methoxon sprayings on the height of oil flax at stages I- V1 of development. Date Height at time of treatment, average increase per day and final height (cm.) Untreated 2M - 4K kg. per ha. Untreated' 2M - 4K kg. per ha. Y2 1 1 2 % 1 1 2 Stage I Stage II 3.6. 2.6 2.6 2.6 2.6 - - 9.6. +0.3 +0.2 +0.0 +0.0 4.6 4.6 4.6 4.6 14.6. 0.6 0.1 0.3 0.0 +0.6 +0.2 +0.1 +0.1 17.6. 0.4 0.7 0.1 0.4 0.4 0.4 0.3 0.3 22.6. 0.7 0.7 0.8 0.4 0.7 0.6 0.2 0.1 27.6. 1.4 1.3 1.1 0.8 1.4 1.5 1.6 1.2 29.6. 2.4 1.7 1.0 1.6 2.4 1.8 1.4 2.7 7. 1.9 2.2 1.9 1.8 1.9 2.o 1.9 1.8 11. 7. 0.8 0.8 1.5 1.6 0.8 1.2 1.6 1.6 20. 7. 0.1 0.2 0.3 0.5 0.1 0.2 0.4 0.4 41.5 39.9 38.5 38.0 41.5 41.6 42.4 40.8 Stage II/ Stage IV 14.6. 7.6 7.5 7.5 7.6 - _ - - 17. 6. +0.4 +0.2 +0.2 +0.1 - - - 22.6. 0.7 0.6 0.5 0.1 12.5 12.5 12.5 12.5 26. 6. - - +1.2 +0.8 +0.5 +0.1 27.6. 1.4 1.4 0.9 1.1 2.3 1.0 0.8 0.1 29.6. 2.4 2.1 1.9 1.7 2.4 2.o 1.5 2.o 7. 1.9 2.0 2.1 2.0 1.9 2.1 2.2 2.o 11. 7. 0.8 1.0 1.4 1.5 0.8 1.1 1.0 1.2 20.7. 0.1 0.2 0.2 0.2 0.1 0.1 0.3 0.3 41.5 41.8 41.3 39.9 41.5 40.7 39.9 38.5 Stage 17 Stage VI 26. 6. 17.1 17.1 17.1 17.1 - - - - 29.6. +2.4 +1.7 +0.8 +0.2- - - - 2. 7. - - - - 30.5 - 30.5 30.5 30.5 5.7. 1.9 2.2 2.1 1.9 +1.8 +0.6 +0.3 +0.2 11.7. 0.8 0.9 1.2 1.4 0.8 1.1 1.4 0.9 20. 7. 0.1 0.0 0.1 0.1 0.1 0.3 0.3 0.5 41.5 40.9 39.9 38.8 41.5 41.3 J 42.8 41.0 When the possibilities of using artificial hormones for weed control in oil flax cultivations are investigated, it is important to know, what effect such substances have on the amount and quality of the crop of oil flax, with special regard to seed crop. For the present experiment these facts are shown in Tables 5 and 6. Seed crops were expressed on 90 % dry basis and 98 % purity. Stem crops were weighed air-dry. As a significant delay in maturity was caused in many experimental plants 4.j q.) Tr ea te d p la n ts e n te re d ye llo w m at ur it y ea rl ie r ( 4 -) . o r la te r (— ) t h an u n tr ea te d . p la nt s (d ay s) S od iu m s al t of 2 , 4 -D kg . p er ha . TI 0 r-I 1 + + + Csi '-' I 1 T-I T-I C7 T-I 0 0 +++ I 2M - 4K N 0 0 0 0 LO CO 0 IIH TI 0 0 0 0 0 0 0 IIII . I I I A ve ra ge p er io d o f fl ow er in g (d ay s) So di um s al t of 2 ,4 -D kg . p er ha . 1-1 CO •TI1 T.I 0 0 0 co CO T}I 0 0 co co .,- != TII rri N - 1 2 ,-CD CO ,11 CO 0 TI1 Til Til co ..,ti •,1‹ ,ti 0-, 0 0 CO CO 0 CO 1`.- c.D U nt r e at ec i. T-1 CO CO 1-1 T-I T-I 1--i .TI "-I y-1 1-1 1-1 T-I 1--1 Fl ow er in g -in t re at ed p la nt s be gu n ea rl ie r or la te r (± d ay s) t h an i n u nt re at ed p la nt s So di um s al t of 2 ,4 -D kg . p er h a. TI + 1 + 1 0 0 — 1 0 — 1 — 2 0 0 0 0 — 1 0 0 + 1 + 1 — 1 + 1 + 1 + 1 + 1 — 2 + 1 + 1 0 — 1 — 11 — 19 — 26 S pr ay ed du ri n g fl ow er in g ,•].. ,..., I-I ,II 1 1 N TI Ti 0 0 •'. IT E 0 Q E . 0 ,,,, å — I 2. 6 II 4. 6 II I 7. s IV 1 2. 5 V 1 7 .1 V P ) 3 0. o V II ') 41 .5 I6 17 by artifieial hormone treatments, if applied at stages VI and VII of develop- ment - e. g. a number of green leaves were left on the stems - the stern, crops of these stages are not reported here. Table 5. Effect of artificial hormones on the yield of seed and stem 1) of oil fla,x cultivations treated at stages 1-VII of development. Differences printe,cl in fat are significant at least at 5 % level of probability. Stage of development and height at time of treatment Untreated 2M-4K • I kg. per ha. Sodium salt of 2,4-D kg. per ha. yr, I 1 I 2 I % 1 Y ield of seed kg. per ha. ± kg. Rel. I per ha, I ± kg. Rel. I per ha. Rel. ± kg. per ha. Itel. ± kg. ± kg. Rel. per ha. per ha. hei. I 2.6 1 170 100 + 160 113 + 200 117 + 40 103 - 150 87 -400 66 II 4.6 1 330 100 + 150 112 +190 115 + 80 106 - 10 99 + 60 105 III 7.8 1 110 100 + 130 111 +140 113 +100 108 - 20 98 - 50 95 IV 12.5 1 160 100 + 160 113 + 120 110 + 130 110 + 70 106 + 50 104 V 17.1 1 230 100 + 100 108 + 60 105 + 10 101 ± 0 100 - 20 98 2) VI 30.0 1 230 100 + 30 103 + 50 105 -110 92 - 600 52 -850 31 3)1/11 41.5 1 100 100 - 100 91 -260 76 -380 65 - 130 89 -540 51 rield f 8 teM 1 2.6 2 020 100 + 150 107 +170 108 + 40 102 -190 91 -340 83 II 4.6 2 090 100 + 220 111 +300 114 + 150 107 + 110 105 + 90 104 III 7.8 1 830 100 + 190 111 +200 111 + 120 107 + 50 103 - 60 97 11/ 12.5 1 860 100 + 170 109 +200 111 +230 112 + 80 104 - 10 99 V 17.1 1 890 100 + 30 102 + 70 103 + 110 106 - 30 98 -120 93 1 Stage et develop- ment Minimum significant difference at 5 % level of probability kg. F-value • m % Yield of seed Yield of stem Yield of 1 Yield of seed stem Yield of Yield of seed stem I II III IV V VI VII 164 120 100 129 119 141 125 314 190 138 133 171 - -- 16.63*** 4.19* 6.14** 1.94 1.25 67.17*** 23.46*** 3.69* 2.sc(*) 5.15** 5.57** 2.29 - -- 4.8 2.8 2.9 3.4 3.2 4.7 4.8 6.2 2.s 2.4 . 2.2 3.o - - BONNIER, G. and TEDIN, 0. 1910: Biologisk variationsanalys. 326 pp. Stockholm. - Handledning i förs5ksteknik. Lantbrukshögskolan, Vordbruksförsöksanåtalten. Meddelande No. 1, 203 pp. Norrtälje 1939. 1 and 2 kg. of morpholine salt of 2.4-D pek ha. 1/2 and 1 kg. of morpholine salt of 2.4-D per ba„ 724-...49 3 42 18 40 H eig ht in c en tim e t r 30 20 10 3;) 38 10 20 30 Days after treatment Fig. 2. Effect of methoxon sprayings (1 and 2 kg. per ha,.) on height of oil flax cultivations at stage I of development. Table 6. Effect of artificial hormones, sprayed at stages I-1711 of develop- ment, on the quality of seed crop and on the yield of oil. Stage of 2M-4K kg. per ha. Sodium salt of 2,4-D 231-4K Sodium salt development and height Untreated kg. per ha. .,21, kg. per ha. of 2,4-D kg. per ha, 1 I 2 5/2 I 1 at time '0, of treatment Average weight proportion of sound (= S) -`4 and membranous (= 31) seeds in orop (%) 1 I 2 % 1 1 cm, 1=> S 31 S M S M SI 31 I S M Weight per 1000 seeds gm . I 2.6 86 2 83 2 75 5 82 3 76 5 5.0 4.9 4.8 4.8 4.5 II 4.6 87 2 83 2 81 2 80 2 80 1 5.1 5.1 5.o 5.2 5.1 III 7.8 90 1 85 1 87 1 90 1 89 1 5.1 5.1 5.o 5.0 5.0 IV 12.5 87 1 90 1 87 1 90 1 88 1 5.1 5.2 4.9 4.9 4.9 V 17.1 89 1 90 1 88 1 86 1 87 0 5.1 5.2 4.9 5.1 5.1 1) VI 30.o 87 1 73 2 44 13 29 10 15 21 5.2 5.0 4.3 4.6 3.9 2)VII 41.5 90 1 41 18 31 28 75 3 11 14 5.1 4.5 4.4 5.5 4.5 Yield of oil (kg. per ha.) and relative number 011 content % I 2.6 443 100 +72 116+ 9 102 -59 87-158 64 42.8 42.6 42.4 42.7 42.0 III 7.8 430 100 +49 111+30 107 -10 98 -26 94 43.9 43.4 43.3 43.6 43.4 V 17.1 474 100 +22 105+ 1 100 - 4 99 -10 98 43.7 43.7 43.5 43.4 43.6 1 and 2 kg. of morpho inc salt of 2,4-D. Y2 and 1 kg. of morpholine salt of 2,4-D. Ex per iment 2. - The seven different stages of development of the previous experiment• were treated, as mentioned on p. 12, during about six weeks under somewhat clifferent climatic conclitions. In order to eliminate the differences in climatic conditions between clifferent treat- ments, another experiment similar to experiment 1 was conducted, in which sprayings were applied siroultaneously to plants being at four differ- 40 19 ent stages of development. The experiment was sown in mouldy clay soil on May 22, June 1, June 11 and June 21, at ten days' intervals, at the rate of about 100 kg. of 100 % germinating and pure seed per hectare. The plants were arranged in plots of 5 D1,2 in size and the treatments — a = untreated, b—d = %, 1, and 2 kg. of 2M-4K given as Agroxon, e 1 kg. of sodium salt of 2,4-D, and f = 1 kg. of morpholine salt of 2,4-D applied as aqueous solution at the rate of 1 000 1. per hectare — were placed in four blocks. Spray application was made by m.eans of Ginge knapsack sprayer on July 1. The average height of plants at the time of treatment and temperature on the day of treatment and two following days are given below: Mean temperature on day of Stage of Average height of plants at treatment and two following development time of treatment (cm.) days (0°) 3.0, cotyledon stage 19.5 5.3II 19.5 III 19.2 19.5 IV 30.5, bud stage 19.5 Thus stages 1—TV of development approximately correspond to the stages I, II, V, and VI in the eXperim,ent 1. — The effect of artificial hor- mones on the stem curvature and recovery, density, height, flowering, and yellow maturity are shown in Tables 7-10. Table 7. E ffect of artificial hormones on stem curvature and recovery of oil flax plants being at stages 1.-1V of development at time of treatment. Bate of stem bending expressed according to the same scale as in Table 1 on p. 13. Stages of development are the same as above. Stage of develop- 2M-4X kg. per ha. Sodium salt of 2,4-D kg. per ha. Morpholine- salt of 2,4-D kg. per ha. i ment and date Y2 I 1 I 2 1 Average pereentage of degrees of stem curv ture 0-4 in 400 plants 0 1 2 3 4 0 112 13141 0 1 2 3 41 0 112 314 0 1121 3 4 1 1.7. 100 100 100 100 100 3.7. .5 69 23 3 1 20 67 12 0 23 58 17 2 3 44 43 9 1 0 31 53 14 2 6.7. 39 56 5 11 77 8 3 1 8 40 43 6 3 3 54 36 5 2 2 59 29 6 4 7. 7. 50 46 4 12 80 6 2 7 61 27 4 1 7 54 33 3 3 4 57 27 6 6 12. 7. 100 --- — — — — — — — — — — — — 14. 7. 100 — — — — — — — — — — 15.7. 100 16 84 42 40 8 3 7 Not com le ely recovered ) II 1. 7. 100 100 100 100 100 2.7. 59 38 3 16 71 12 1 0 460 36 93 7 0 29 56 15 3.7. 69 30 1 16 65 19. 0 769 24 95 5 0 15 69 16 6. 7. 100 89 11 22 70 8 — — 13 68 19 7. 7. 100 26 69 4 0 1 100 — — — 8.7. 58 38 4 8 80 11 0 1 12.7. 100 — — 14. 7. 100 20 231-4K kg. per ha. Sodium salt of 2, 4-D Morpholine- salt of 2,4-D Stage of kg, per ha. kg. per ha. develop- ment and date 1/2 ' I 1 I 2 1 1 Average percentage of degrees of stem curvature 0-4 in 400 plants 011121 3141 011121 3141 0111213141 0111213 4 0 112 3 4 III 1. 7. 100 100 100 - 100 100 2. 7. 6 42 51 1 0 3 82 15 0 0 0 94 6 90 10 0 0 0 85 15 3. 7. 18 79 3 17 67 15 1 0 0 9 85 6 95 5 0 0 3 79 18 4. 7. 90 10 31 61 8 0 3 29 66 2 100 0 0 17 68 15 6. 7. 100 76 24 0 6 72 22 0 3 13 84 7.7. 87 13 0 12 78 10 0 1 10 89 12.7. 100 — — — — — — 15.7. 75 25 39 55 6 21.7. 100 — — 6.8. 100 IV 1. 7. 100 100 100 100 100 7. 0 0 0 100 0 0 0 100 0 0 0 100 0 100 0 0 0 100 4. 7. 27 69 4 0 2 93 5 0 0 46 54 0 97 3 0 0 2 98 6.7. 59 41 0 20 80 0 0 89 11 49 51 0 0 41 59 7. 7. 91 9 0 46 54 0 0 94 6 76 24 0 0 0 100 15.7. 100 89 11 14 83 3 100 0 12 88 27. 7. 100 — — Not completely 8. 100 recovered Table 8. Effect of artificial hormones on the relative density of oil flax cultiva- tions being at stages I—IV of development at time of treatment. Average density before treatment at stage I = 167, at stage II = 184 plants per row meter. Stages I—IV are the same as on p. 19. Relative density of oli flax cultivations at time of harvesting Sodium 1 Morpholine salt of 2,4-D kg. per ha. 2M-4K kg. per ha. Stage of development Untreated 100 100 100 73 98 100 92 87 98 100. 100 100 98 95 100 100 100 100 Mor- Sodium pholine salt of 2,4-D kg. per ha. 2M-4K kg. per ha. 1/2 1 1 1 2 1 1 Date Un-treated 7. 7. 4. 7. 7. 7. 14. 7. 17. 7. 20. 7. 23. 7. 26. 7. 29. 7. 2. 8. 7. 8. 3.0 4.1 5.5 13.3 17.6 27.o 35.7 45.1 50.7 56.3 59.1 7. 7. 4. 7. 7. 7. 14. 7. 17. 7. 23. 7. 29. 7. 2. 8. 7. 8. 18.2 22.1 28.5 33.2 40.9 42.1 44.1 46.7 47.9 50.0 . 2M-4K . per ha. Mor- Sodiura pholine salt of 2,4-D kg. per ha. Un- treated Stage II before spraying 6.9 4.1 8.4 9.6 7.3 9.6 11.3 9.1 10.4 21.1 16.2 19.6 29.1 28.3 30.3 38.5 35.8 37.8 44.2 41.8 42.8 50.0 47.4 47.2 53.0 49.o 50.8 53.1 50.2 51.o 53.2 50.9 51.1 Stage IV before spraying 28.9 28.2 33.9 31.6 28.8 38.9 33.8 29.1 40.5 38.8 35.o 42.7 39.8 38.3 43.0 42.o 40.6 43.4 45.o 42.0 44.0 45.8 42.4 45.2 45.8 42.8 45.5 5.3 8.5 9.7 12.7 22.4 31.2 39.1 48.4 51.2 52.5 52.s 53.0 30.0 33.0 39.1 42.3 43.0 43.5 44.1 44.4 44.s 45.1 7.7 10.0 11.2 21.9 31.1 39.1 46.8 50.7 51.2 51.6 51.8 30.3 35.3 37.7 41.5 42.0 43.0 46.2 45.4 45.5 4.2 7.4 8.o 13.5 22.1 27.5 37.3 45.0 47.s 48.3 48.8 28.1 28.4 28.6 31.6 37.0 37.4 39.2 39.8 39.s Stage I befoie spraying 3.6 4.2 12.9 15.5 28.5 33.6 39.7 49.2 55.0 69.2 2.9 4.2 11.7 12.9 20.o 29.7 39.4 48.0 54.8 57.8 2.7 3.4 9.0 11.8 17.0 24.9 33.2 44.2 51.5 55.0 2.s 3.3 6.5 9.3 10.7 15.7 18.8 34.5 44.0 45.9 2.7 3.2 4.8 5.3 15.8 23.2 35.2 45.5 46.2 Stage III before spraying 20.6 16.5 15.4 22.0 25.4 22.3 14.6 28.0 29.2 24.5 18.8 30.2 37.9 36.1 29.0 37.5 40.8 39.6 35.0 38.8 42.8 43.2 39.8 39.2 45.5 47.7 45.2 40.7 46.8 47.8 45.8 43.1 47.o 48.2 45.9 43.6 14.7 14.8 17.8 23.9 26.6 31.1 38.o 38.8 38.9 21 Table 9. Effect of artificial hormones on height of oil flax plants being at stages of development at time of treatment. Figures printed in fat and subsequent figures indicate the real height of the plants, above fat figures the height of the bent plants. Table 10. Effect of artificial hormones on flowering and yellow maturity of oil flax plants being at stages I-IV of development at time of treatment. Stage of development and height at time of treatment cm. Flowering in treated plants begun on the average later than in untreated plants (days) Average, period of flowering (days) Treated plants entered yellow maturity on the average later than un- treated plants (days) 231 - 4K kg. per ha. Sodi- um salt of kg. per Morp- holine 2,4-D ha. ! U n tr ea te d 2M - 4K kg. per ha. Sodi-IMorp- um iholine salt of 2,4-D kg. per ha. 2M - 4K kg. per ha. Sodi- um salt of kg. per Morp- holine 2,4-D ha. Y2 1 2 1 1 14 I 1 2 1 1 % 1 2 1 1 I 3.0 II 5.3 III 19.2 IV 30.5 0 0 0 0 0 1 2 1 1 1 4 14 1 1 0 0 2 3 14 21 13 12 14 11 13 15 15 23 15 14 14 21 16 15 18 27 20 15 16 16 18 15 18 19 ,0 0 1 3 0 2 3 10 0 4 5 18 3 0 1 3 3 4 7 20 Figures indicating the average rate of stern curvature on each o bserva- tion day were obtained by rnultiplying the proportion of differen t stern 22 curvature by the degree of curvature (0-4).: For methoxon sprayings these figures are shown graphically in Figure 3. 3 \ \ in, 19 cm. \ \II, 5em. \ \ 0 2 4 6 8 10 12 14 0 2 4 6 8 10 0 4 8 12 16 20 0 4 8 12 16 20 21 28 32 Recovery in days Fig. 3. Effect of artificial hormones on stem curvature and recovery of oil flax cultivations at stages I—IV of develepment. Figures indi- cate the average rate of stem curvature. Broken lin = Y2, unbroken line = 1, and dotted line = 2 kg. of 2M-4K per ha. The results reported in Tables 3 and 9 are based on usual rough measur- ing. They are averages of 20 individual plants selected at random in different replicate plots. In order to obtain as accurate results as possible, another experiment was conducted in connection with experiment 2, in which the effect of methoxon sprays of different concentrations on marked individuals was observed. Treatments: a -= untreated, b— 6-- 1/5, %, 1, and 2 kg. of 2M-4K as Agroxon per ha. Measurings — the first m,easuring on July 19 at 15 just before treatm,ent, and after treatment every morning at 9 at first, later at intervals of 2-4 days during 22 days — were made irom a board placed on piles, which were hit in the ground and on a level -with it. The thickness of the board was added to each result of measuring. 23 Figures 4-7 show best the stem b3nding and recovery of oil flax treated at stages I—TV of development. Fig. 4. Stem curvature and recovery of oil flax treated at stage I. Dying plant in the center. % natural size. Comparable with stage I in experiment 1. Fig. 5. Stem curvature and recovery of oil flax treated at stage II. 1/, natural size. Comparable with stage II in experiment 1. Fig. 6. Stem bending - and recovery of oil flax treated at stage III. 1/, natural size. Comparable -with stage V in experiment 1. Fig. 7. Stein curvature and recovery of oil flax treated at stage IV. 1/5 natural size. Comparable with stage VI experiment 1. 24 25 The averages of measurings, which in each plot were made for 32-34 individual plants, are given in Table 11. Table 11. Some observations about effect of artificial hormones (applied at the rate of 115 , %, 1 and 2 kg. of 2111-4K per ha.) on height of oil flax. Days after treatment Height at time of treatment, average inerease per day and final height (cm.) Untreated 2M-4K kg. per ha. '/5 Y2 1 2 0 1) 1 22.7 2) 1.3 23.6 1.6** 22.4 2.2*** 19.0 1.5* 17.8 1.6** 2 2.0 1.1 0.6 0.9 0.9 3 1.8 1.7 0.7 0.4 • 0.2 4 1.6 1.4 1.0 0.3 0.2 5 2.0 1.9 1.7 0.6 0.4 6 1.8 2.3 1.9 1.3 0.6 7 1.8 1.5 1.4 0.9 0.8 8 1.9 2.2 2.1 1.7 0.8 9 2.8 3.3 3.0 2.7 1.7 10 2.1 2.7 2.9 2.6 2.3 11 1.7 1.8 2.1 2.3 2.5 12 1.2 1.4 1.8 2.0 2.0 14 1.2 1.3 1.3 1.8 2.1 16 0.9 1.1 1.7 1.5 1.7 18 0.6 0.6 0.7 1.0 1.0 22 0.3 0.3 0.4 0.8 1.0 31 i 52.9 53.s 51.7 49.7 50.2 18 hours after treatment. Subsequent measurements after 24 hours. Mean differences (m) on the average are: untreated = +0.077, 0.02 % = ±0.070, 0.05 % = ±0.068, 0.1 % ---;±0.o72 and 0.2 % = ± 0.osi. The effect of artificial hormones on the amount of the seed, stem, and oil crop of oil flax, and on the quality of seed and oil crop for experiment 2 is shown in Tables 12-15. Table 12. Effect of artificial hormones on yield of seed and stem 1) of oil flax plants being at stages of development at time of treatment. Differences printed in fat are significant at least at 5 % level of probability Stage of develop- ment and height at time of treatment cm. Untreated 231-4K kg. per ha. Sodium I Morpholine salt of 2,4-D kg. per ha. 1/2 1 ( 2 1 1 Yield of seed kg. per ha. " ± kg. per ha. Rel. ± kg. Rel. ± kg. per ha. 1 per ha. Rel. kg. per ha. kg. per ha. [tel. I 3.o 1 480 100 + 50 103 + 150 110 + 70 105 - 200 86 - 360 76 II 5.3 1 670 100 + 30 102 + 40 102 - 90 95 - 140 92 - 410 75 III 19.2 1 500 100 - 150 90 -270 82 -300 80 - 140 91 - 920 39 IV 30.5 1 520 100 - 250 84 -290 81 -580 62 - 420 72 -1220 20 Yield of stem I .... 4 690 100 + 290 106 - 90 98 -460 90 -12301 74 -1520 68 II.... 4 730 100 -410 91 -570 88 -690 85 - 8201 83 -1090 77 III .... 2 500 100 -150 94 - 80 97 +270 111 - 170 93 - 340 86 IV .... 2 100 100 + 100 105 + 570 128 + 640 131 + 140 107 + 300 115 1) Minitnum significant differences for yields of seed and stem required for significance 4 at 5 % level, F-values, and m % are given below: Stage of development and height at time of treat- ment 2M-4K kg. per ha. 2 Sodium salt 2,4-D kg. per ha. 1 Morpholine salt of 2,4-D kg. per ha. 1 Untreated Refractive number I 3.0 II 5.3 III 19.2 IV 30.5 1.4839 1.4839 1.4839 1.4838 1.4835 39 39 40 40 4U 32 33 32 32 31 30 31 31 30 32 26 Table 13. Effect of artificial hormones on the gvality of yield of seed. Plants were at stages 1-1V of development at time of treatment. Average weight proportion cf s.ound (= S) and membranous (= M) seeds in yield Weight per 1 000 seeds for the whole crop (= A) the sound seeds (= S), and membranous seeds (= M) Treatments I 3.0 cm. II 5.3 cm. III 19.2cm. TV 30.5cm. III III IV SMSMSM S M A SM A S M A A Untreated 30 11 56 4 73 5 90 1 4.4 5.2 3.3 5.1 - 4.8 5.0 % kg. of 2M-4K 30 14 50 6 73 3 83 3 4.4 5.1 3.2 5.1 - - 4.9 5.0 1 -»- 27 13 41 4 73 4 82 5 4.6 5.1 3.2 4.8 5.1 3.3 4.8 4.6 2 --»-- 27 13 37 7 67 11 66 16 4.6 5.2 3.3 4.7 5.1 3.3 4.7 4.5 1 kg. of sodium ' salt of 2,4- D. 15 18 29 6 79 4 83 6 4.4 5.2 3.2 4.8 5.1 3.3 5.0 5.2 1 kg. of morp- holine salt of 2,4-D per ha. 13 26 20 11 23 23 19 37 4.1 5.2 3.0 4.5 5.1 3.2 3.6 3.5 Table 14. Effect of artificial hormones on oil content and yield of oil. Prepara- tions sprayed on plav,ts being at stages I-IV of development. stage of develop- ment and height at time of treatment cm. t Untreaed Sodium Morpholine 2M-4K salt of 2,4-D salt of 2,4-D kg. per ha. kg. per ha. kg. per ha. 1 1 2 1 1 1 oi 1 co,.. tent % 011 kg.per ha. Rel. 011 con_ tent % 011 kg. per ha. Rel. Oil con- tent % 011 kg.per Rel. ha. 011 CM- tent % 011 kg.per ha. R el. 011 con- tent % 011 kg. per ha. Rel. I 3.o II 5.3 III 19.2 IV 30.5 41.9 43.3 41.7 42.3 646 639 553 567 100 100 100 100 42.0 43.3 41.9 41.5 + 58 + 13 - 98 - 116 111 102 82 80 42.4 43.3 41.9 40.6 + 32 - 36 - 108 - 232 106 94 80 59 42.o 43.3 41.9 41.6 - 72 - 54 - 51 - 165 87 92 91 71 41.5 42.0 40.5 39.o - 135 - 172 - 347 - 463 75 73 37 18 Table 15. Effect of artificial hormones on the degree of unsaturation of oil indicated by refractive numbers. Preparations sprayed on plants bei,ng at stages 1-1V of development. Afinimum sigmficant difference kg. F-values m % Stage of development Yield of seed Yield of stern Yield of seed Yleld of stern Yield of seed Yield of stem 271 575 3.49* 14.33*** 7.1 4.9 213 791 45.54*** 2.02° 7.2 6.4 221 396 15.24*** 2.390 6.9 5.4 186 441 35.86*** 3.24(*) 6.6 6.1 27 The purpose of the two experiments reported on pages 12-26 has been to find out, whether oil flax is resistant to 2M-4K and 2,4-D compounds applied at different stages of development as sprays of different concentra- tions. Before the obtained results are surveyed, a third experiment is reported, in which the artificial hormones were given as dusts. Experiment 3. — The experiment was arranged according to row. method, the size of plots being 5.4 m2, nuraber of replicates 4. Treatments: a untreated, b—c treated by giving through veil bags 2 and 4 kg. of 2M-4K (as Agroxon), the amount of carrier being 200 and 400 kg. per hectare, d—g = treated by giving 1, 2, 2, and 2 kg. of sodium salt of 2,4-D per hectare, the amount of carrier being 100, 200, 100, and 50 kg. per hectare. The average height of the plants at the time of treatment: Average height of Stage of Date of plants at date of development treatment treatment (cm:) I June 6 3.o II June 11 4.2 III June 20 . 7.5 The effect of dusts on the treated plants was slow at ali three stages of development. Only a slight curvature was observed and buds opened in ali plots almost simultaneously. Therefore, only the figures indicating yield of seed are given in Table 16. Table 16. Effect of dust applications of artificial hormones on yield of seed. Treated at stages of development, and treatments a—g are the same as above. Differences printed in fat are significant at 5 % levet of probability. Stage of develop- ment and height at time of treatment cm. a b c 1 d •e f g Yield of seed kg. per ha. Rel. ± kg. per ha. -n , r`m,. ± kg. per ha. ''• per ha. -"I. -0,, kg. per ha. Rel. Der ha. Rel. ± kg. per ha. Rel• I 3.0 114.o III 7.5 1 160 1 060 1 250 100 100 100 +230 —90 + 60 120 92 104 +200 +90 +100 117 109 107 —160 +40 +120 86 105 110 —130 +40 +110 88 104 108 — 90 +150 +120 92 115 109 — 40 + 30 +150 96 103 111 Minimum significant differences at 5 % level of probability, F-values, and m % of yields of seed are: Stage af developmet Minimum significant difference (kg.) F-value 1 m% 217 4.20 6.1 II 276 . 0.70 8.2 III 160 0.89 3.9 28 Discussion In the three experiments reported on pages 12-27 different concentra- tions of methoxon and chloroxon compounds were applied to oil flax plants at different stages of development in order to find out their effects on the development of the plants, on the amount and quality of seed and stem crop, and on the quality of seed crop. These facts are of considerable value, when the importance of artificial hormones with regard to weed control in oil flax is investigated. Effect on stern, curvature and recovery As the results given in Tables 1 and 7, and in Figures 1 and 3 inclicate, the plants attained the greatest degree of stem curvature within 1-3 days after treatm,ent. II a m,ethoxon compound (Agroxon) was used, the average rate of steni curvature was usually intensified and the time needed for recovery prolonged, if the am,ounts of effective substance per unit surface area were increased. Significant clifferences in average degree of stern, curvature were also observed between different stages of develop- ment. In experiments 1 and 2 the average rate of stem curvature for 1-A), 1, and 2 kg. of 2M-4K applied at comparable stages of development was this: I and I =-.12 and 13 days, II and II = 8 and 7 days, V and III = 6 and 12 days, VI and IV = 15 and 24 days. In the experim,ent 2 the time needed for recovery was distinctly longer for plants at the stages III and IV than for the plants at the com,parable stages V and VI in the experi- m,ent 1. At stages I and II no differences in average stem curvature of plants were observed between experiments 1 and 2. — Of 2,4-D compounds the effect of morpholine salt applied to oil flax at cotyledon or bud stage was so great that the plants did not recover completely, but remained m,ore or less creeping on the ground. Also at other stages of development the effect of m,orpholine salt spray on the stem curvature was greater than that of a methoxon spray of double concentration. The recovery of oil flax was prevented by a solution of the sodium salt of 2,4-D applied at cotyledon stage. At other stages of development its effect, however, was not so great as that of a comparable amount of 2M-4K. This is probably explained so that the aqueous solution of soclium salt of 2,4-D calmot enter the plants to any considerable extent except at cotyledon stage. This question will he considered again later (cp. p. 44). — In experim,ent 1 none of the applied compounds caused stern, curvature at stage VII of development. Experiments conducted in TJ. S. A. (2, 9, 10, 15, 18) have shown that growth r-egulators travel with assimilation products probably 29 along the phloem, into the stem causing bencling in it, and that the rate of bencling increases with quickened absorption and translocation of the effective substance. The quickest effect was observed under conclitions favourable for photosynthesis. Treatment with 2,4-D caused no or hardly any curvature in dark, in cold, if CO2 was lacking, or in stem,s treated after the leaves had been cut off. Plants treated at stage VII had already attained their final height by the tim,e of treatment, which probably accounts for the non-curvature in these plants. — As Tables 2 and 8 show, ali plants in the recovered plots, however, did not recover, but a num,ber of them died, especially if the treatment was applied at cotyledon stage. Effect on height The results of the effect of artificial bormones on the height of oil flax cultivations, applied at different stages of development, are given in Tables 3, 9, and 11. Within 18 hours after treatment (Table 11), 0.0 2, 0.05, 0. 1, and 0. 2 % methoxon sprays appar- ently caused a distinct stimulation in the growth of oil flax treated when 20 cm. high. Especially the average height of plants treated with the 0.05 %'solutionincreased consider- ably more (= 2.2 ± 0.068 cm.) than that of untreated plants (= 1.3 + 0.077 cm.). During the next seven days, however, the average height of the plants in untreated plots increased distinctly more than the height of other plants. Also other results (Tables 3 and 9) affecting the height of plants show distinctly that, on the whole, growth during the next few days after treatment occurred at a slow rate, if high concentrations of spray applications were used. So the treated plants remained much smaller than the untreated ones. This phenom,enon, however, was not permanent, for the average height of the plants treated before they had attained their final height increased considerably, and on the whole this increase was greatest in plants treated with the highest con- centr atio n of the spra y. Table 11 shows for instance that 11-22 days after treatment the average height of plants treated with 0.2 % solution showed the greatest increase ( = 18.1 cm.), that of the untreated plants the smallest increase ( = 9.5 cm.). Thus in the reported experiments the final height of plants treated with 0.2 % methoxon spray was at the most 4 cm. lower than that of the untreated plants. If treated with a concentration of 0.1 %, they rem,ained only 2 cm. lower, at the most. On the other hand, salt solutions of 2,4-D, particularly m,orpholine salt, had clistinctly injurious effects on the height of oil flax. 30 Effect on flowering and reaching of yellovv maturity In experiment 1 flowering was delayed 2 days at the ‘most owing to treatments applied at stages I—V of development. Treatment at bud stage, especially if 0.2 % 2M-4K and 0.1 and 0.2 % morpholine salt solu- tions of 2,4-D were used, resulted in a more significant delay of 11-26 days. In experiment 2 the delay caused by 2 kg. of 2M-4K and 1 kg. of morpholine salt of 2,4-D per hectare seemed to be more significant, if the applications were made shortly before opening of buds. 0.1 % methoxon spray delayed flowering for 2 days, at the most, aqueous soclium salt spray of 2,4-D for 1 day at the most (cp. p. 44). Delay in yellow maturity also seems to have been dependent on the date of treatment, the delay being more significant, if the treatment -was given shortly before opening of buds, and if the amounts of effective sub- stance used per unit surface area was large. Effect on the amount of seed and stem crop The crop results of the experiments 1-3 are given in Tables 5, 12, and 16. Morpholine and sodium salt sprays of 2,4-D caused the most significant reductions in seed and stem crops. In experiment 1 no reduc- tion in seed or stem crop was caused by treatments with sodium salt solu- tion of 2,4-D applied at the rate of I/2 and 1 kg. per hectare, if the plants were treated at stages II—V of development (== 4.6-17.1 cm.). On the other hand, at stage I, and at the comparable stage in. experiment 3, as well as at all stages in experiment 2 the effect was distinctly injurious. Also other investigators (3, 8, 14) emphasize the dangerousness of 2,4-D solutions to oil flax. The seed crop was r e du ced owing to methoxon treatments in experiment 1 only if given at flowering stage (= VII) in experiment 2, if given to plants which had attained the height of 19-31 cm. (= stages 'III and IV). Reduction in stem crop was only detectable owing to a treat- ment given at stage II. The seed crop was incr e ase d in experiment 1 by ali methoxon treatments given at stages (2.6-7.8 cm.), and in. experiment 3 by treatments given at stage I (3.0 cm.). It is not certain, however, whether the increases in yield (40-80 kg. per ha.) obtained from the experimental plot d (= 2 kg. of effective substance per ha.) in experiment 1 at stages I and II are due to spray applications. On the other hand, the incre ase s in yield obtained from experimental plots c and d (= kg. and 1 kg. of the effective substance applied as spray, or 1 kg. 31. and!.), kg. of the effective substance applied as dust) are certainly due to treatments and show a variation of 130 — 230 kg. per hectare, or 11-20 %, the av'erage in crease being 1.75 kg. per hectare, or 15 %. Also in the experiment 2 the plots treated by methoxon at stage I produced• 50-150 kg. m,ore seed per hectare than the untreated'plots, though the differences cannot be considered significant. The stern crop was increased in experiment 1 by all treatm,ents with 0.05, 0.1, and 0.2 % methoxon sprays applied at stages I—V (2.6-12.5 cm.),') though the increases obtained at stage I and with a concentration of 0.2 % at stage II and III cannot he considered significant. The proved increases were on the average 210 kg. of air-dry stems per hectare, or about 11 %. In experiment 2 the air-dry stem crop was increased by spray applications made with 0.1 and 0.2 % solution of methoxon at stage IV (30.5 cm., bud stage) with approximately 600 kg. per hectare. The development rhythm of the plants was thoroughly clisturbed and their growth points at least partly destroyed owing to the treatment, but when the plants recovered, they developed numerous side branches near the growth point, and owing to these the crop increased. Man.y investigations have been hitherto published dealing with the question of the importance of growth-regulating substances. More or less distinct increases in crops have been reported, but, on the whole, these increases have been attributed to the disappearance of weeds from,- the treated areas. The increases in yield reported above in eonnection with experim.ents 1-3 cannot, ho w- ever, he due to more favourable growing con.di- tions as a result of eradication of weeds, because ali plots (also the untreated ones), as already mentioned, were as well as possible kept free from, weeds, which were pulled off with hands as soon as they appeared..The increases in yield are tkerefore most probably due to •the stimulation caused by right amounts of methoxon compounds applied at a suitable stage of development. The thought that the growth of cultivated plants can he stimulated and their yield increased by artificial hormones is not a new one. American distributors of some of the preparations have reported, for instance, in- cremed yields and utore vigorous growth of plants as a result of growth regulator treatment, though such claims have not been hitherto confirmed (1, p. 7). _ÅBERG (22, pp. 56-57) describes the increases in yield (41 'and 52 %) obtained in an experiment on .bean with very small amounts of methoxon and 2,4-D,2) and observes that they are •probably due to the The increase is probably due to a slight inerease in the diameter of stems. 1 1. of AGROXON and 0.1 kg. of WORMOSAN G per ha. 32 growth-stim,ulating effect of these preparations. Also Seger oats produced an increase in yield of 270-520 kg., or of 6-11 %, if 1-4 kg. of Wormosan O (40 % 2,4-D) per hectare was applied to an area not heavily infested with weeds. In this instance the increase in yield, therefore, could not be due to larger growth space obtained with killing of weeds. Very interesting is the question of the effect of different growing condi- tions on the smaller or greater increase in yields of different plants caused by treatments with various araounts of growth-regulating substances. The answer to this question also answers the question of the r e a 1 growth- reducing effect of weeds. The increases in yields reported hitherto are not necessarily due only to more favourable growing conclitions caused by killing of weeds. Likewise, in experiments, in which the relative nurn,ber of a crop treated with artificial hormones was e. g. 90, the growth-reducing effect of the preparation may have been greater than 10 %, but owing to the increase in yield due to more favourable growing conditions caused by eraclication of weeds the final relative num,ber of yield was 90. Valuable inform,ation with regard to these facts will be obtained in field experiments with two parallel plots, one of which will be kept free from weeds. In experiment 1 definite increases in yield were obtained, if oil flax was treated with 0.05-0.2 % methoxon solution at early stages of develop- ment. But why were such increases not obtained, or obtained to much less extent, in experiment 2 from plants treated in the sam,e manner and at com' parable stages of development? As the results given in Tables 1 and 7 and in Figures 1 and 3 indicate, the greatest degree of average stem curvature was usually attained within 1-3 days after treatment, after which the plants began to recover. The figures below show the mean temperature prevailing on the day of treatment and during two following days in experiments 1 and 2. Stage of development Experiment 1 Experiment 2 I/I 16.2 00 19.5 00 II/II 18.8 19.5 V/III 18.o 19.5 VI/IV 19.8 19.5 The mean temperature on the day of treatment and two following days was in experiment 1 lowest for cotyledon stage (I), or 16.2° C, highest, or 19.8° C, for bud stage (VI), which was nearly the same as for all stages of developm,ent in experiment 2. Yet the results obtained in experiment 2 for cotyledon stage showed the greatest similarity to those obtained in. experiment 1, and the least similarity for bud stage. Reduction in yield does not seem to be due to higher mean temperature prevalent on the day of treatment and two following days. G ro w th in c en ti m et re s 33 Figure 8 shows the curves inclicating the rate of growth for untreated plants in experiments 1 and 2 during 6 days following treatment. 0 2 4 6 0 2 Days atter treatment Fig 8. Average rate of growth of untreated plants in experiments 1 and 2 during 6 days following treatment cm. per day. Figure 8indicatesthat during the next few days follo w- ing treatment growing occurred at a higher rate in the untreated plants of experiment 2 than in the comparable plants of experiment 1. The figures on p. 34, :which give a summing up of the results reported hitherto, confirm that the potential of development must have been for the un- treated plants of experiment 2 quite different from that of the comparable plants of experiment 1: 4 724-49 5 34 Co m pa ra b l e st ag es o f de ve lo pr ce nt in e xp er i-, m en ts 1 a n d 2 A ve ra ge h ei gh t a t t im e of tr ea t ir en t (c m .) A ve ra ge he ig h t at ye llo w m at ur ity (c m .) Ti m e be tw ee n tr ea t- m e n t an d ye l lo w m a t nr ity ( da y s ) A ve ra ge in cr ea se in he ig ht p er d ay b et w ee n tr ea tm e n t a n d y el lo w m a t ur it y (c m .) Yield of seed Yield of stern kg. per ha. kg. per ha. I 2.6 41.5 71 0.55 1 170 100 2 020 100 I 3.0 59.1 74 0.76 1 480 126 4 690 232 II 4.6 41.5 65 0.57 1 330 100 2 090 100 II 5.3 53.o 67 0.71 1 670 126 4 730 226 1: V 17.1 41.5 49 0.50 1 230 100 1 890 100 2: III 19.2 50.0 58 0.53 1 500 122 2 500 132 1: VI 30.o 41.5 42 0.27 1 230 100 1 990 100 2: IV 30.5 45.2 38 0.39 1 520 124 2 100 106 The rapiclity of growth at a given stage of development is determined by the joint effect of prevailing climatic and edafic factors, and it is greater under favourable conclitions. Vigorous growth e. g. depends upon vivid assimilation and rapid translocation of assimilation products from, leaves. Many american investigations (2, 9, 10, 15, 18) show that the artificial hormones absorbed in leaves are translocated with assimilation products probably along the phloem into the stem, and that the effectiveness of translocation depends on the number of assimilation products transferred from the leaves in one unit of time.1) This accounts among other things for the greater influence of artificial growth regulators on plants growing at a sunny place than on plants of like speeies growing in the shade. Like- -wise for the greater susceptibility of plants to the influences of artificial hormones in spring and in surn,mer, when their photosynthetic action is vigorous, as compared to the end of the growing season, when little food is produced by plants. The results of the present investigations reported above h,ave shown that a definite stimulation to height was caused by artificial hormones within 18 hours after treatment, that the final yield of seed and stern, from plants treated at early stages of developrnent (2.o- 12.5 cm.) increased, if growing occurred at the rate indicated in Table 3 and in the figures given above. If plants of the same height, but being otherwise in m,ore active state of growth,, were treated in the same man- ner, the effect was often opposite : the yield was reduced. This is probably due to the slower rate of growth ih the treated plants of experiment 1 as compared to the plants of experiment 2. Thus the plants of experiment 1 had time to utilize a part of the artificial growth regulator a.bsorbed by them to larger extent than the plants of experiment 2, and the injurious 1) No reserve food is transferred into the stem from very young, actively growing leaves (10). 35 influence of too large amounts of artificial hormones was mitigated. sIn experiment 2 the translocation of artificial growth regulators into the stern, probably occurred more acutely and resulted in more vigorous effects-. We may also think of such a possibility that the amount of hormones produced .by the plants themselves was in experiment 2 at the time . of treatment larger than in the plants of experiment 1, as the plants of experi- ment 2 were in more vigorous state of growth. Therefore also the increase in the amount of artificial hormones had a more vigorous effect. Experiment 1 was sown at normal time (May 22), and the earliest stages of development were treated under normal conclitions prevailing in Southern Finland at that time.') The last plots of experiment 2, how- ever, were sown about a month later than normal. Thus the results obtained in experiment 1 probably give the most accurate picture of the possibilities of using artificial hormones for weed control in oil flax in. Southern Finland. According to experiment 1 1/2 — 1 k g. of methoxon co rapound (Agroxon) .applied as an aqueous solution at the rate of 1 000 1. per hectare to plants of the height of 2.6-12.6 cm. had no injurious e'ffects on the yield of seed and'stem, on the contrary, both in- creased, the former on the average by 160 kg. or about 14 % per hectare, the latter by about 210 kg. or about 11 % per hectare. As the concentra- tion of 1/2 kg. per hectare is not sufficient to kill less sensitive weeds, 1 kg. per hectare is the most re 00 mmendable amount. Acconling to the results of experi- ments 1 and 2 in application of artificial hormones attention must,however,not be pai.d exclusively to the compound applied, to the amount used, or to the height and stage of development of the treated plants, but also to the rapidity of growth, which is determined by both climatic and edafic factors. Actively gro wing plants are more sensitive than plants growing slo wl y, and thus smaller araounts of the effective substance are to be used for the former than for the latter. The obtained results agree -with those reported by BLACKMAN and HOLLY (3), as far as the amount and quality of the effective substance are concerned. They declare, however, that it .is of great importance to 1) Average climatic conditions prevalent during growth season 1948 at Tikkurila and deviations from normal. Month Temperature C° Normal 1948 Precipitation mm. Normal 1948 May 8.4 + 0.9 47 ± 0 June 12.8 + 2. o 53 —29 July 16.1 —0.3 70 —28 August 13.8 + 0.5 88 + 21 36 wait until the oil flax plants are 3-4 inches (= 7.5-10 cm.) high before they are sprayed, and spraying must have ceased before they reach 12 inches 30 cm.). The results of the experim,ents conducted in Scancli- navia (8) suggest that oil flax should be sprayed, when plants have attained the height of 7-10 cm., at the latest. This agrees with the results reported above. The amounts recommended to be used in Scanclinavia, 5-8 1. of Agroxon per hectare (8, 22, 23) seem, to be somewhat small for Finland. On the other hand, treatment with normal amounts of dinitro-ortho-cresol (DNOC) applied to fibre flax cultivations in Sweden in warm spring 1948 resulted in death of plants in several districts, and this warns us that in some years the safety margin between the recovery and death of rather sensitive plants treated with selective herbicides may be extremely narrow. Effect on the quality of crop Classification of seeds. On the whole, the reduction in the proportion of sound seeds and the increase in the proportion of membranous seeds was dependent on the concentration of the applied methoxon solution so that higher concentrations increased the proportion of membranous seeds and decreased that of sound seeds (Tables 6 and 13). Treatment exerted the most injurious effects at bud and flowering stages. 1Vlorpholine salt of 2,4-D exerted the greatest influence, whereas sodium salt had injurious effects only if applied at cotyledon stage. Weight per 1 000 seeds. With an increase in the proportion of membra- nous seeds the weight per 1 000 seeds decreased correspondingly. As far as sound- seeds are concerned, the treatments had no injurious effect on the weight per 1 000 seeds (Tables 6 and 13). Oil content (Tables 6 and 14) in the crops obtained from the plots of experiment 2 treated with morpholine salt of 2,4-D showed the most significant reduction. (at bud stage in some instances 2.3 %) owing to a considerable increase in the proportion of membranous seeds. Methoxon compound had no injurious effect on the oil content of seeds, except when applied at bud stage. The results do not disagree with the results reported by other investigators (8, 22). Refractive numbers (Table 15) indicate that the degree of unsaturation of oil was reduced some units by ro.orpholine salt of 2,4-D, if applied at cotyledon stage, which is probably due to higher temperature in vegeta- tions thinned by treatm.ents, as compared to other vegetations (12, pp. 12-13, 65, 70). Differences between clifferent stages of developm‘ent, on the .other hand, are quite distinct and agree with the results reported earlier (12, p. 17). 37 With regard to the am.ount and quality of crop weed control in oil flax cultivations should he exercised with 1 kg. artificial hormon.es of metho- xon type, and th.ese substances should he applied to plants at an early stage of development (3 — 1 3 cm.). 2. Experiments with oil flax treated at siynilar stage of development Experiment 4. — The purpose of this experiment was to find out the effect of different amounts of 2M-4K on the yield of seed, if oil flax cultivations at the same stage of development were sprayed with different amounts of 2M-4K in the morning or at dusk. The plots, 5.4 m2 in size, were arranged acconling to row method, number of replicates 4. Treatments: a = untreated, b = 0.75 kg. per hectare sprayed in the morning, c = the same applied at dusk, d and e = 11/2 kg. per hectare applied in the morning and in the evening, and f and g = 3 kg. per hectare. Treatment applied with Ginge knapsack sprayer, on July 5, the average height of plants 18 cm. The effect of the treatment on the yield of seed is shown in Table 17. Table 17. E /teet of spray aplications of 0.75, 11 /2 , and 3 kg. of meth,oxon compound on yield of seed.') M = sprayed in the morning, E = in the evening. 2M-4K kg. per ha. yield of seed kg. per ha. Relative number 0 1 550 1) 100 0.75 M + 90 106 0.7 5 E + 50 103 1.5 M —340 78 1.5 E —400 74 3.o M —980 37 3.0 E —870 44 Discussion Treatment with 0.075 % solution did not result in reduction of the yield of seed, but 0.15 and 0.3 % solutions had extremely injurious effects. Though the plants were at a very sensitive stage of developinent (8 days before opening of buds) at the tim,e of treatm,ent, and effective substance was applied at the rate of up to 3 kg. per hectare, similar t rea t- ments in the morning and in the evening did not prciduce different effects on the amount of yield. 1) Minin= significant difference at 0.05 level of probability 175 kg., F-value — 55.59***, m % = 4.9. 38 Experiment 5. — The purpose of the experiment was to find out, whether artificial hormones used for weed control in oil flax cultiva- tions can he applied by means of a horse-operated sprayer. The plots, 63.4 m 2 in size, (untreated plots 31.7 m2) were arranged accoriling to row method, number of replicates 4. Treatments: a = untreated, b—d = treated by means of horse-operated TT-Favorit sprayer with 0.5, 1, and 2 kg. of 2M-4K (.P 46) applied at the rate of 700 1. per hectare. Plants were rather high at the time of treatment, June 29, on the average 15 cm. The experimental area was not heavily infested with weeds. Their number was counted only for an area of 1 m2 in each treatment. Results are given below: Speeles of weed 23I-4K (P46) kg. per ha. 0 Y2 1 2 Number of weeds per m2 Chenopodium album 1 6 4 0 0 Erysimum cheiranthoides 6 2 0 0 Galeopsis sp. 2 1 1 0 Spergula arvensis 4 2 0 0 Polygonum convolvulus 3 2 2 1 Stellaria media 9 6 1 0 Viola arvensis 12 4 2 1 Polygonum lapathifolium 1 0 1 1 Together 53 21 7 3 Relative number 100 40 13 6 Also weed seeds were stored at threshing and assortment, and the average yield per bectare of weed seeds from different plots show fairly accurately 1) the effectiveness of artificial hormones with regard to different species. The results reported above, as well as the effect of spray applica- tions on the amount and quality of the seed crop of oil flax, are gi-ven in Tables 18 and 19. Table 18. Effect of P 46 spray on yield of seed of oil flax. TrEated by means of horse-oper ated Favorit sprayer Treatments Yield of seed Quality of crop kg. per ha. Rel. number Sound seeds Membra- nous seeds Weight per 1 000 seeds gm. Germina- tion Untreated 2) 1 430 100 . 75 4 4.8 93 1/2 kg. of 2M-4K + 20 101 80 3 4.8 95 1 + 60 104 78 3 4.8 95 2 » —»— per ha. + 30 102 81 4 4.7 97 The real seed crop of weeds scattering their seeds early and easily is not always found oult by means of this method. Minimum significant difference at 5 % level of probability 43 kg., F-value 3.58°, m % 0.9. 39 Table 19. Effect of 1A-2 kg of 2M-4K (P 46) on, yield of seed of the most common, weeds i experiment 5. A.pplications made by means of horse-operated Favorit sprayer. Speeies of weed Yield of seed kg. per ha. ( = a), relative number (= b), and proportion of eaeh speeies in the whole yield of weeds % (= c) Untreated 2M-4K kg. per ha. % 1 2 Chenopodium album L a 74.20+6.84 6.00+2.03 0.13+0.03 0.16+0.06 b 100 * 8 0 0 c 62.6 20.0 1.2 2.1 Erysimum cheiranthoides L a 15.65+2.70 3.00+0.01 0.53+0.14 0.25+0.15 b 100 19 3 2 c 13.2 10.0 5.0 3.2 Galeopsis sp. a 1.97+0.46 0.40+0.13 0.02+0.01 0 b 100 20 1 0 c 1.7 1.3 0.2 0 Spergula arvensis L a 0.53+0.21 0.25+0.04 0.05+0.02 0.05+0.02 b 100 47 9 9 c 0.4 0.8 0.5 0.6 Polygonum convolvulus L . a 23.28+3.77 16.98+2.00 7.63+0.82 5.55+0.62 b 100 73 33 24 c 17.7 56.5 72.2 72.1 Stellaria media (L) Vili a 0.83+0.18 0.70+0.12 0.40+0.14 0.18+0.15 b 100 84 . 48 22 c 0.7 2.3 3.8 2.3 Viola arvensis (Mun.) a 0.58+0.09 0.65+0.16 0.18+0.03 0.07+0.01 Gaud. b 100 112 31 12 e 0.5 2.2 1.7 0.9 Polygonum lapathifoliurn L a 0.93+0.00 0.75+0.18 1.15+0.20 0.58+0.35 b 100 81 124 62 c 0.8 2.5 10.9 7.5 Fumaria officinalis L a 0.48+0.01 1.25+0.09 0.43+0.00 0.80+0.10 b 100 260 90 167 c 0.4 4.2 4.1 10.4 Galium spurium L a 0.02+0.01 0.09+0.02 0.05+0.02 0.06+0.02 b 100 300 250 300 c 0.0 0.2 0.5 0.8 Together a 118.47 30.04 10.57 7.70 b 100 25 9 7 `Discussion Though spray applieations virere made, when the average height of the plants was already 15 cm., none of the amounts used (0.5-2 kg. of the effective substance per ha.) reduced the seed crop of oil flax, or 40 had any injurious effect on its quality. It is even probable that the seed crop increased owing to the treatment by 20-60 kg. per hectare, though the differences are not proved. Of the weeds Chenopodium album, Erysimum cheiranthoides and Galeop- sis sp.1) were eraclicated or lost seeding capacity to considerable .extent already owing to treatment with 1 kg., Polygonum convolvulus, Spergula arvensis, Stellaria media and Viola arvensis to less extent. The three last m,entioned species are generally considered rather resistant (11). In t his experiment the usual treatment with 1 kg. reduced their seed crop on the average to 1/3, treatment with 2 kg. sometimes to 1/7 of the average crop obtained from untreated plots, and the num,ber of weeds to 1/8 and to 1/23 of the untreated plot. Polygo- num lapthifolium, Galium spurium, and Fumaria officinalis were resistant. This experiment confirms convincingly the results of earlier experiments, according to which it is not dangerous to use artificial hormones for weed control in oil flax cultivations, if only the treatment is given well before bud stage and effective substance is applied at the rate of 1 kg. of 2M- 4K per hectare. 0. Im,portance of carrier to the effectiveness of artificial hormones with regard to oil flax In connection of the survey of literature it was rnentioned that oil flax, on the whole, is most resistant to methoxon compounds (Agroxon, P46), which should he applied at the rate of 0.5-1.0 kg. per hectare (8, 13, 14, 16, 23), or in some instances at the rate of 2 lb. per acre (= about 2.2 kg./ha.) (3). 2,4-D compounds are not recommended at ali, or they should he applied in much smaller amounts. According to BLAOK- MAN and HOLLY even 0.1 % solution of sodium salt or acid suspension of 2,4-D can he applied at a susceptible stage of development (= 3-4 inches to 12 inches or 7.5-10 cm. to 30 cm.), but ester-oil em,u1sions are quite unsuitable. Also the results of the present experiments indicate that 2,4-D com- pounds had in general more injurious effects on the development of oil flax, and on the yield of seed and stern, than 2M-4K compounds. A sixth experiment was conducted in order to compare the effectiveness of a methoxon compound (P 46) with that of a 2,4-D compound (P 47) with regard to oil flax. Experiment 6. — The substances were sprayed with a Ginge knapsack sprayer on plants, 29 cm. in height, at bud stage (= 4 days 1) G. speciosa Mill., G. tetrahit L., and.G. bifida Boenn. 41 before flowering) on July 9. Treatments: a = untreated, b and d =0.75 and 1.5 kg. of the soclium salt of 2,4-D, c and e = 1.5 and 3.o kg of 2M 4K per hectare. Size of plots 5.4 112, 2, number of replicates 4. The effect of the sprayings on the yield of seed is given in Table 20. Table 20. Effect of spray applicaticns of 2M-4K and 2,4-D (P 46 and P 47) on yield of seed of oil . flax.1) Treatments a = Untreated yield of seed kg. per ha. Rel. number 1 680 100 b = 0.75 kg 2,1-D per ha. —160 90 c = 1.5 » 2M-4K » » —130 92 d = 1.5 » 2,4-D » » —230 86 e = 3.o » 2M-4K » » —460 72 The 2,4-D compound P 47 seemed to be more effective than the 2M- 4K compound P 46. Among the other results reported previously we also find opposite results. So, for instance, in. experiment 1 1 kg. of the soclium salt of 2,4-D in aqueous solution did not result in so marked stern, curvature at stages III—V than 1 kg. of 2M-4K per hectare (Table 1). In the same experim,ent a treatment with 2,4-D did not retard maturity when applied at stages II—V, whereas a treatment with 2M-4K caused significant retardation (Table 3). The same was observed for stages 11—TV in experi- m,ent 2 (Tables 7 and 10). But at cotyledon stage 2,4-D proved more effective than methoxon in experiments 1 and 2: it resulted in thinned vegetations, in injurious effects on stern, curvature and recovery, and on the yield of seed and stern. Experiment 7 was conducted in order to find out the reason for such sudden decrease in the effectiveness of artificial hormones applied at a later stage of development. Experiment 7. — Experimental plots, 1.s m2 in size, in which the average height of the plants was about 15 cm., were sprayed on July 22 with a = aqueous solution of the soclium sait of 2,4-D, b and c .= the same added with 1 % of emulsifying oil, d = aqueous solution of the m,orpholine salt of 2,4-D applied at the rate of 2 kg. per hectare. Two adjacent plots A and B were sprayed in each treatment. 15 minutes after treatment the plants of B-plots were irrigated by giving there& an am,ount of water corresponding to 10 mm. heavy rain. 3 days after treatment sarn,ples showing stem curvature were taken from plots A and B in each treatment. These sam.ples are shown in figures 9-11. Minimum significant difference at 5 % level of probability = 137 kg., F-value = 12.65***, m % = 3.0. 6 Fig. 9. Effect of aqueous solution of the sodium salt of 2,4-D on stem curvature of oil flax. Rate of applica- tion 2 kg. of compound per ha. dissolved in 1 000 1. water. Plants B (2 plants on the right) were subjected to 10 mm. artificial rain 15 minutes after treat- ment. Ä = not irrigated. Samples taken three days after ;treatment. natural size. Fig. 10. Effect of aqueous solution of the sodium salt of 2,4-D, added with 1 % emul- sifying oil, on stem curvature of oil flax. Rate of application 2 kg. of compound per ha. dissolved in 1 000 1. water. Plants B (3 plants on the right) were subjected to 10 mm. artificial raja 15 minutes after treatment. A not irrig,ated. Samples taken three days after treatment. natural size. 4 B Fig. 11. Effect of aqueous solution of the morpholine salt of 2,4-D on stem curva- ture of oil flax. Rate of application 2 kg. of compound per ha. dissolved in 1 000 1. water. Plants B (3 plants on the right) were subjeeted to 10 mm. artificial rain 15 minutes after treatment. A = not irrigated. Samples lakon three days after treatment. natural size. The effect of sprayings on the height of oil flax is shown in Figure 12. 104 104 10 II 89 Fig. 12. Effect of 0.2 % 2 4-D spray applica,t'ons on heigl t of oil flax measured 11 days I) and 26 days (= II) after treatment. Treatments: 1 = untreated, 2 = aqueous solution of the soditun salt of 2,4-D, 3 = 2 + emulsifying oil 303, 4 = 2 + emulsifying oil Panfix, 5 = aqueous solution of the morpholine sait of 2,4-D. Height of untreated plants 1 I 48 cm., and of 1 II 57 cm. = 100. Shaded = not irrigated, unshaded = irrigated. Table 21 shows the effect of 2,4-D spray applications on the opening of buds. Tabk 21. Effect of 2,4-D spray applications on opening of &tele in plants 1,5 cm. in h,eight at time of treatment. Flowering delayed as compared to untreated plants (days) Treatments A not irrigated B trrigated 0.2 % aqueous solution of sodium Salt of 2,4-D 1 0 Previous + 1 % emulsifying oil 303 9 3 The first + emulsifying oil Panfix 22 5 0.2 % aqueous solution of morpholine salt of 2,4-D 14 11 44 Discussion As Figures 9-12, and Table 21 inclicate, only a slight stern, curvature, retardation in growth or delay in flowering was caused by 2 kg. of soclium salt of 2,4-D per hectare applied as an aqueous solution to plants, which were on the average 15 cm. high. 15 minutes after treatment B-plots were subjected to 10 mm. artificial rain, and the artificial hormone com- pound on the surface of plants was so completely washed away by the irrigation that no effect was observable. When spreading agent (1 % em,u1sifying oil) was added to the aqueous solution, the compound entered the tissues more easily and resulted in distinct stem curvature of the third degree (cp. p. 13), a very significant retardation in growth, and delay in flowering. •The oil Panfix seem ed to increase the effectiveness of 2,4-D compound more than 303. An irrigation given to B-plot 15 minutes after treatment slightly decreased the effectiveness of the selective herbicide, as shown. by stem curvature, retardation in growth, and delay in flowering, but owing to the spreader some of the herbicide, at least, was absorbed by the plant tissues or attached to the surface of the plants to such extent that all of it could not he washed away by the irrigation. Morpholine spray applications proved m.uch more effective than comparable soclium salt spray applications, even better than the latter used together -with the spreader 303. An irrigation given to B-plot 15 minutes after treat- ment decreased the effectiveness of the substance, but a clistinct stem bending of the second degree, retardation in growth and considerable delay in flowering were observed. With regard to the height of all treated plants it was observed, as mentioned already earlier (cp. p. 29) that though treatments at first resulted in retardation of growth, this was no permanent phenomenon, and later growth becam,e so vigorous that final differences in height between treated and untreated plants were clearly sm,aller than a short time after treatment. The results of this and other experim,ents (1, 17, 20) suggest that the low effectiveness of an aqueous solution of 2,4-D on oil flax at other than cotyledon stages, which was observed in experiments 1 an 2, may be due to the fact that the solution cannot easily penetrate the surface tissue. At cotyledon stage, when the tissue is still delicate, a 0.1 % solution of the sodium salt of 2,4-D was more effective than comparable Agroxon spray, at other stages much less effective.1) Owing to spreader the prepara- tion is spread on the surface of the plant in a thin film, so that the liquid does not turn into drops and roll to the ground as easily as a pure water solution, which has a greater surface tension. In the experiment 6 the 2,4-D compound (P 47) was more effective than the 2M-4K compound (P 46); it probably contains some substanee decreasing surface tension (spreader). 45 The preliminary experiment reported above, as well as the experim.ents 1,2, and 6indicate that with regard to the effectiveness of artificial hormones both the com.poun.d itself and the carrier used are of extreme importance. The better the spray is attached to the plant, the more evenly it is spread on the surface of the plant, and the better it is absorbed by the tissues, the more effective it seems to be. If 2M-4K and 2,4-D compounds are absorbed by the tissues with equal ease, 2,4-D compounds seem to be much more effective than rnethoxon compounds.') 1)111 this connection a short mention may be made of the effect of isopropyl N-phenyl carbamate (IPPO) on oil flax. In a pot experiment oil flax appeared to be almost as sensitive as wheat, whereas pea resisted the substance well, and even clearly stimulated by it. The results agree with those reported by ENNIS (6). Thus IPPO cannot be recommended for eradication of quack-grass (Agropyrum repens (L.)) and other graminous weeds from oil flax cultivation Summary The first detectable effect caused by artificial hormones, stem curvature, was observed to begin within 1/2-6 hours after treatment. The deepest degree of stern, curvature was observed 1-3 days after treat- ment. Spray 'application of the morpholine salt of 2,4-D produced the most injurious effects, especially if applied at cotyledon and at bud stage, and plants rem.ained ro,ore or less creeping on the ground. Likewise, when an aqueous solution of the sodium, salt of 2,4-D was applied to plants at cotyledon Stage, the plants did not recover completely, but when applica- tions were made at other stages, it was less effective than comparable amount ( = 1 kg. per ha.) of 2M-4K, which is due to the fact that aqueous solution is not easily absorbed by plant tissues. The average rate of stem curvature caused by 2M-4K compound (Agroxon) was at a given stage of development greater, if large amounts of the substance were sprayed to plants per unit surface area. At cotyledon and bud stages the plants were most susceptible to stem curvature, and at these stages also the tim,e needed for recovery was longest. Plants were least susceptible to stem curvature imm.ed.iately after cotyledon stage, when the average height of the plants was 5-8 cm. The plants treated at the end of flower- ing period did not show any stem curvature, nor was any signifieant eur- vature apparent at any stage of development, if dusts were used for treat- ments. Ali individual plants in the recovered groups of plants, however, did 'not recover, but path of them died, especially if treated at cotyledon stage. The average percentage for treatments with 0.1 % methoxon spray was 4, for treatments with comparable am.ount of 2,4-D spray 13. Sprayings with 0.1 % compounds applied immediately after cotyledon stage did not result in any thinning in. vegetations. Sprayings with 0.02-0.2 % solutions, especially with 0.05 % solu- tion, of methoxon resulted in definite stimulation in the growth of oil flax within 18 hours after treatment. — In general the rapidity of growth in the treated plants was during the days follo-wing the treatment dependent on the concentration of the spray, so that higher concentration retarded the growth and the treated plants remained much shorter than the un- treated plants. Before the final height was recovered, however, the average height of the treated plants increased, and the increase was greatest for 47 plants treated with highest concentration. Thus the final height of plants treated with 0.1 % 2M-4K remained only up to 2 cm. shorter than that of the untreated plants, whereas the plants treated with 0.1 % aqueous solution of 2,4-D remained up to 11 cm. shorter. The effect of artificial horm,ones on the flowering and yellow maturity of oil flax was, on the whole, very injurious, if large amounts of the compound were used per unit surface area, and if the treatment was given shortly before bud stage. 0.1 % methoxon sprays given at an early stage of developm,ent (3-13 cm.) delayed flowering for 1 day, at the most, and yellow m,aturity for 2 days, at the m,ost. Treatments with 0.05-0.2 % methoxon at an early stage of deve- lopm,ent (3-13 cm.) did not result in any injurious effects on the amount of the yield of seed and stem,, or on the quality of seed. On the contrary, under conditions, under which the growth of oil flax during the next few days after treatment occurred at the rate of 0.3-0.6 cm. per day on the average, depencling on the stage of development, especially methoxon sprays of 0.05 % and 0.1 % concentrations caused a definite increase in yield, 130-230 kg. of seed or 11-20 %, and 170-300 kg. of stem per hectare, which is probably due to stimulation. Sprayings given at a very late stage of developm,ent (= some days before appearance of buds, and especially at bud or flowering stage) had an injurious effect on the amount of yield of seed and stem, as well as on the quality of seed, especially if the treatment was given under conclitions favourable for rapid growth, or if the substance used was a com.pound of 2,4-D. The effects caused by similar am,ounts of artificial hormones applied on the sunny morning or on the evening of the same day did not show any clifferences with regard to the amount of yield. In the spraying experiment, in which the amount or the quality of yield of oil flax was not injuriously affected by a treatment -with 2M- 4K, applied at the rate of 0.5-2 kg. per hectare, many of the weeds occurring in the experim,ental area were killed or lost their seeding capacity. Thus a treatment with 1 kg. of 2M-4K was sufficient for Chenopodium album, Erysimum cheiranthoides and Galeopsis sp. The seed crop of Poly- gonum convolvulus, Spergula arvensis, Stellaria media and Viola arvensis, which are considered rather resistant, was on the average reduced by a treatment with 1 kg. per hectare to 1/3, by 2 kg. to 1/7 of the average seed crop obtained from, the comparable untreated plots, and their nurnber decreased to 1/8 and to 1/25 of the untreated plot. Resistant were Polygo- num lapathifolium, Galium spurium and Fumaria officinalis. 1 kg. of the sodium sait of 2,4-D in aqueous solution resulted in more injurious effects than a comparable amount of 2M-4K given as .A.groxon, if applied at cotyledon stage. At other stages it proved less effective than 2M-4K. If emulsifying oil was added to the aqueous solu- 48 tion of the soclium salt of 2,4-D, the effectiveness of the compound in- creased considerably. Owing to the added oil the compound also became more resistant to rainfall. 8. At least in Southern Finland and in areas with similar climatic conditions artificial hor- mones seem to be of considerable importan.ce with regard to weed control in oil flax cultivations. The best results are achieved by applying 1 kg. of 2M-4K per he ct are at an early stage of develop- me nt (3-13 cm.). Literature Cited AVERY, GEORGE S. Jr. and JOHNSON, ELIZABETH B. 1947: Hormones and horticulture. - First edition, 326 pp. New York and London. BEAL, J. M. 1946: Reactions of decapitated bean plants to certain of the substituted phenoxy compounds. - Bot. Gaz. 108: 166-186. BLACKMAN, G. E. and HOLLY, K. 1948: Weed Control in Linseed and Flax. - Agriculture LIV, 12: 538-542. BREITENSTEIN, WALTER 1947: Agroxone -tehokas rikkaruohomyrkky. -Kas- vinsuojelu-uutiset N:o 9: 4-7. ENNIS Jr., W. B. and Bovn, F. T. 1946: The response of kidney-bean and soybean plants to aqueous-spray appliCations of 2,4-dichlorophenoxy- acetic acid with and without Carbowax. - Bot. Gaz. 107: 552-559. Exisns Jr., W. B. 1948: Responses of crop plants to O-Isopropyl N-phenyl carbamate. - Bot. Gaz. 109: 473-493. HOFSTEN VON, C. G. 1948: Försöksverksamheten och upplysningen rörande kampen mot ogräs. - Lantmannen. 31: 511-513. JACOBSON, GEORG and BJÖRKLUND, CARL M. 1948: Hormonderivaten i kam- pen mot ogräsen. - Off-print of Skånska Dagbladet 2. 4. 48, Malmö. MARTH, P. C. and DAVIS, F. F. 1945: Relation of temperature to the selective herbicidal effects of 2,4-dichlorophenoxyacetic acid. - Bot. Gaz. 106: 463-472. MITCHELL, Jo= W. and BROWN, JAMES W. 1946: Movement of 2,4-dichloro- phenoxyacetic acid stimulus and its relation to the trånslocation of organic food materials in plants. - Bot. Gaz. 107:.393-407. OSVALD, HUGO and ÅBERG, EWERT 1948: Kampen mot ogräset. - Växt- odling 3: 74-92. Uppsala. PAATELA, JUHANI 1947: On the Possibilities of Growing Oil Flax in Finland- On the Quality of Finnish Linseed Oil and some Factors affeeting it. - Off-print of the publication of Scientific Agric. Soc. of Finland Acta Agralia Fennica 68, 1: 1-106. Helsinki. PETERSEN, INGVAR') H and DALBRO, SVEN 1948: Hormon Praeparater i Land- og Havebrukets Tjeneste. - Udgivet af det Kg1 danske Land- husholdningsselskab. 84 pp., Kobenhaven. RASMUSSEN, L. 1947: Oversigt over Resultaterna af Landboforeningernes Forsogsvirksomhed paa Sjaelland 1947. - Off-print of Beretning om Landboforeningernes Virksomhed for Planteavlen paa Sjaelland 1947, p. 321. RICE, ELROY L. 1948: Absorption and translocation of ammonium 2,4-dichloro- phenoxyacetate by bean plants. - Bot. Gaz. 109: 301-314. Statens Forsogsvirksomhed i Plantekultur 1948: 417. Meddelelse. SWANSON, CARL P. 1946: Two methods for the determination of the herbicidal effectiveness of plant growth-regulating substances in oil solution on broad- leaf plants. - Bot. Gaz. 107: 560-562. 742-49 7 50 WEAVER, ROBERT J. and DeRosE, II. ROBERT 1946: Absorption and transloca- tion of 2,4-dichlorophenoxyacetic acid. — Bot. Gaz. 107: 509-521. WEAVER, ROBERT J. 1946: Effect of spray applications of 2,4-dichloropheno- xyacetic acid on subsequent growth of various parts of red kidney bean and soybean plants. — Bot. Gaz. 107: 532-539. WEAVER, ROBERT J.; MINARIK, C. E.; and Buil). F. T. 1946: Influence of rainfall on the effectiveness of 2,4-dichlorophenoxyacetic acid sprayed for herbicidal purposes. — Bot. Gaz. 107: 540-544. WEAVER, ROBERT J.; SWANSON, CARL P.; ENNis Jr., W. B. and Bovn, F. T. 1946: Effect of plant growth-regulators iii relation to stages of develop- ment of certain dicotyledonous plants. Bot. Gaz. 107: 563-568. ÅBERG, EWERT; HAGSAND, ERIK and VÄÄRTNÖU, HERMAN 1948: Hormon- derivat i kampen mot ogräs, V. Fältförsök 1,946-1947. — Växtodling 3: 8-64. Uppsala. ÅBERG, EWERT; SUNDELIN, GUSTAV; JACOBSON, GEORG; BJÖRKLUND, C. M. and GELINDER, C. Fr. 1948: Hormonderivatens användning i jord- bruket. — Försök och Forskning 5, 3: 17-19. Suomenkielinen selostus Maatalouskoelaitoksen kasvinviljelysosastolla Tikkurilassa ryhdyttiin profes- sori OTTO VALLEn toimesta v. 1946 tutkimaan tekohormonien merkitystä rikka- ruohoj en torjunnassa. Kokeita on jatkettu vuo'sina 1947 ja 1948. Niissä on kiin- nitetty päähuomio tekohormonien vaikutukseen eri- rikkaruoholajeihin, varsinkin öljypellavalla tavattaviin. siemenrikkaruohoihin. — Tekohormonit ovat keinolli- sesti valmistettuja orgaanisia yhdisteitä, jotka vaikuttavat kasveissa tavatto- man pienissä määrin esiintyvien hormonien (auksiinien) tavoin, mutta joita ei ole tavattu-kasveissa. Tekohormonit tuhoavat sopivan suuruisina määrinä annet- tuina useat rikkaruohot, mutta eivät yleensä vaikuta haitallisesti viljakasvien kasvuun eivätkä satoon, mikäli levitys on suoritettu viimeksi mainittujen ollessa nuorella kehitysasteella. • Kaikki ruohomaiset kasvit eivät kuitenkaan ole yhtä herkkiä tekohormoneille: Niinpä eräät rikkaruohot tuhoutuvat varsin helposti jo yz kg/ha suuruisella tekohormonimäärällä, kun taas eräät toiset lajit eivät tuhoudu edes 2 kgiha 'suuruisella määrällä. Samankin kasvilajin kestävyys teko- hormoneja vastaan saattaa kuitenkin huomattavasti vaihdella, riippuen mm. sen kehitysasteesta, kasvimopeudesta sekä käytetystä valmisteesta. — Ruoho- maisista viljelykasveista öljypellava kestää .melko hyvin metoksoni-tyyppisiä tekohormoneja, joilla niin ollen voidaan torjua rikkaruohoja öljypellavaviljelyk- siltä. On vain selvitettävä, kuinka suuria määriä öljypellava normaalioloissa kestää tekohormoneja ilman että sen sadon määrä pienenee tai laatu huononee, ja• toisaalta, kuinka pienillä määrillä rikkaruohot saadaan tuhotuiksi. Käsillä olevan tutkimuksen tarkoituksena on selvitellä lähinnä kysymyksen ensimmäistä osaa, ts. miten ö 1 j y-p ellava kestää, eri kehitysasteilla ollessaan eri suuria teko- hormonimääriä Tutkimukset on suoritettu Maatalouskoelaitoksen kasvinviljelys- osastolla kasvukauden 1948 kuluessa. Seuraavassa yhteenvedossa esitetään saavutetuista tuloksista lähinnä käytän- nön maanviljelijää kiinnostavat seikat, jotka hänen on syytä ottaa huomioon ryhtyessään tekohormoneilla torjumaan rikkaruohoja öljypellavaviljelyksiltään. Ensiksikin mitä valmistetyyppiin tulee, ovat 2M-4K- eli metoksoni-val9nisteet (esim. Agroxone ja P 46) ehdottomasti suositeltavampia kuin 2,4-D-valmisteet, jotka saattavat vaikuttaa hyvinkin haitallisesti öljypellavan siemen- ja varsi- sadon määrään sekä siemensadon laatuun (ss. 17, 25--26). Tekohormonien käytössä on myös erittäin tärkeätä ottaa huomioon, että käsittely suoritetaan oikeaan aikaan, sekä että tehoavaa ainetta käytetään sopiva määrä. Suositeltavin käyttö- määrä on 1 kg lha tehoavaa ainetta 10 litraa esim. Agroxonea tai P 46-valmis- totta) ruiskutettuna 700-1 000 litrassa vettä. Tämä määrä on yleensä myös riittävä useimpien rikkaruoholajien tuhoamiseksi (ss. 38-40). Öljypellava kestää 2M-4K-tyyppisiä tekohormoneja parhaiten nuorella kehitysasteella, sts..sen ollessa 3-13 cm:n mittaista. Tosin tällöinkin käsitellyt kasvustot taipuvat, niiden väri vaalenee ja pituudenkasvu hidastuu, mutta ne ovat ohimeneviä ilmiöitä, jotka eivät vaikuta haitallisesti lopullisen sadon määrään eivätkä laatuun (ss. 1327). Jos käsittely suoritetaan sirkkalehtiasteella (2.5-3 cm), kasvusto kärsii enemmän 52 kuin hiukan myöhemmillä kehitysasteilla. Tämä ilmenee mm. kasvuston harve- nemisena ja voimakkaampana taipumisena (ss. 13-14, 19-20, 22). Sadon mää- rään sirkkalehtiasteellakaan suoritettu käsittely ei kuitenkaan vaikuta haitalli- sesti. Liian myöhään, sts. nuppuasteella tai hiukan ennen sitä suoritettu käsit- tely sen sijaan saattaa vaikuttaa erittäin haitallisesti siemensadon määrään ja laatuun (ss. 17-18, 25-27). Näin ollen käsittely on varminta suorittaa heti sirkka - lehtiasteella taiviimeistään kun öljypellava on kasvanut 13 em:n mittaiseksi. Öljypellavan rikkaruohontorjunnan kannalta on mitä edullisinta, että käsit- tely tekohormoneilla voidaan suorittaa jo kehityksen alkuvaiheessa. Ensiks k i n öljypellavakasvustot saadaan vapautumaan rikkaruohoista hetkellä, jolloin öljypellava hidaskasvuisena ja erittäin huonosti varjostavana saattaa helpoimmin joutua rikkaruohojen tukahduttamaksi. Toiseksi öljypellavalle jää rikka- ruohojen kuoltua käytettäväksi enemmän kasvinravintoaineita ja vettä. Varsin- kin viimeksi mainitun puute matalajuurisen öljypellavan ollessa nuorella kehitys- asteella saattaa vaikuttaa erittäin haitallisesti sen kehitykseen. Näin ollen teko- hormoneilla käsiteltyihin kasvustoihin kehittyvien kukkien lukumäärä, joka mää- räytyy jo varsin aikaisessa kehitysvaiheessa, tulee, samoin kuin siemensatokin, suuremmaksi kuin rikkaruohojen varjostamissa kasvustoissa. Kolmanneks kun käsittely suoritetaan öljypellavan ollessa nuorella kehitysasteella, suurin osa ruiskutteesta tulee käytetyksi rikkaruohojen torjuntaan. . Tällöin nimittäin ruis- kutetta leviää enemmän rikkaruohojen lehdille ja maahan, jossa sen rikkaruo- hoja tappava vaikutus yleensä kestää parin kuukauden ajan, kuin jos ruiskutus tapahtuisi myöhemmin öljypellavan ollessa rehevämpää. Tekohormonien käyttö öljypellavaviljelyksien rikkaruohontorjunnassa on kai- kesta päättäen menetelmä, joka on omiaan lisäämään öljypellavan viljelyvar- muutta. Kun rikkaruohot saadaan pidetyksi kurissa, .öljypellavan kasvuolosuh- teet paranevat, josta johtuen sen sato saattaa, rikkaruohojen runsaudesta ja koosta riippuen, oleellisesti lisääntyä. Suoritettujen kokeiden perusteella näyt- tää myös siltä, että 2M-4K-tekohormonit em. sopivilla kehitysasteilla ja sopivan suuruisina määrinä annettuina kykenevät kiihottamaan öljypellavan kasvua ja siten lisäämään öljypellavan siemensatoa keskimäärin 175 kg /ha eli 15 % (ss. 17, 27). ".7 7. • .14 - • .1.7? W:5g. .44 •••:. 14p t4. 1.44' • " , - g. tr, : 1/4 '745 411 5.4 .,4"; •+,5 • >44 !.-4.4:: ,..47,••4fig5,,.5:" .4"." • 4`I 4-50 , N :4•• .F719 • )052x, 4;4444 54:1