202 PLANT GROWTH SUBSTANCES 



may prolong the process abnormally and any delaying effect of treat- 

 ment might be exaggerated (13). Tandon (45) made fortnightly measure- 

 ments of height in seven varieties of flax sprayed with 0, 4, 8, and 16 oz. 

 of sodium salt, amine salt, and ester of 2,4-D. He concluded that up to 

 8 ounces there is little reduction in height, and as the crop advances 

 towards maturity even the little reduction noticed at earlier stages 

 is practically eliminated. Paatela (40) has also reported that before the 

 final height (of flax) was recovered, the average height of treated plants 

 increased (more than the untreated) and the increase was greatest for 

 plants treated with the highest concentration. 



Chemical and physiological responses of plants to 2,^-D. — The diff"er- 

 ential response of crop plants to applications of 2,4-D may be expressed 

 in factors affecting quality. Most of the work reported has dealt with 

 protein content of wheat and with the oil content and iodine number of 

 the oil in flax. Helgeson et al. (25) and Mitchell and Linder (38) report 

 increases in the protein content of sprayed wheat, but the increase 

 was associated with a reduced yield, an association that would normally 

 be expected. Corns (9) obtained an increase in protein of barley when 

 yields were reduced by more than five bushels. Erickson, Seely, and 

 Klages (19), however, report an increase in protein of wheat without 

 a corresponding decrease in yield. 



The effect on the oil content and iodine number of the oil in flax 

 has been investigated by Tandon (45), Klosterman and Clagett (29), 

 and Paatela (40). Recent studies of the writer and co-workers will be 

 outlined briefly. Tandon found a distinct differential response among 

 seven varieties to the amine and sodium salts apphed at 4, 8, and 16 oz. 

 per acre. The ester of 2,4-D at these rates reduced both oil percentage 

 and iodine number in all varieties tried except the oil in B5128 at 4 oz. 

 per acre. Paatela reported a reduction in oil up to 2.3 per cent when the 

 flax was sprayed with the morpholine salt of 2,4-D in the bud stage and 

 a reduction in the iodine number when treated in the cotyledon stage. 

 Square yard samples were obtained by Klosterman and Clagett from 

 sprayed and unsprayed portions of four fields. The spray was applied at 

 0.175 pounds of 2,4-D acid per acre in the form of the alkanolamine salt. 

 The variety Dakota was grown on two fields and Minerva and Sheyenne 

 on one field each. Stages of growth varied between fields at time of 

 spraying. No significant differences were found in oil percentage; the 

 iodine number of sprayed Dakota was significantly higher than that of 



