Plant Qrowth'Suhstances 



It may be noted that even should indole-acetic acid regain 

 its one-time price of about los. ($2-50) a gram, or about ;f200 

 ($1,000) a pound^, treatment of agricultural seeds on the field 

 scale with a dust or formalin solution containing the recom- 

 mended doses of synthetic growth-substance cannot add 

 appreciably to the cost of dressing. Mercurial dusts, costing 

 about 2S. a pound, are already applied free by many seed- 

 merchants, and the added cost of material, if five parts of 

 indole-acetic acid were incorporated, would not exceed a 

 farthing (half a cent.) per pound of dust. It is, in fact, 

 practicable to give away a very expensive synthetic chemi- 

 cal! 



Work on the treatment of seeds with synthetic growth- 

 substances has been done by Amlong and others (1937, 1938, 

 1939), who investigated mainly the effects of water-soluble 

 potassium salts of indole-acetic, indole-butyric, and a-naph- 

 thyl acetic acids, in 10-^ and lo-^ equimolecular solutions to 

 which had been added traces of magnesium nitrate and 

 manganese chloride. 20 gm. of seed of sugar-beet (2 strains), 

 lucerne, maize, and spring wheat were steeped 24 hours in 

 60 ml. of solution and sown by hand in the field. The results 

 with maize (ears), wheat (grain) were not significant, but both 

 strengths gave remarkable increases (24-62 per cent.) of yield 

 of leaves and root of beet, and of lucerne hay. The authors 

 conclude that the treatments are economically practical for 

 these two crops. Seed treatment was also given to a number of 

 herbs and vegetables grown in pots, and it was concluded that 

 each species has its optimal dose-requirements. 



Sprays of a commercial growth-substance preparation 

 applied from four weeks after sowing gave especially remark- 

 able results with sugar beet (about 60 per cent, increase in root 

 and 80 to over 100 per cent, increase in tops). It was suggested 

 that spraying has a specially beneficial influence upon the tops, 

 and that the effect of seed-treatment is principally upon the 



^The cost is now slightly reduced ; the prices of indole-butyric acid and the 

 naphthyl-acetic acids are similar. There is reason to think that a-naphthyl- 

 acetic acid should now cost shillings (a few dollars), rather than many 

 pounds (hundreds of dollars) per pound. A cheapening of the other sub- 

 stances can scarcely be looked for. 



48 



