The Treatment of Seeds 



containing about 2-5 parts of growth-substance per million of 

 dust, and grew them on in sand. Stimulation of the early 

 stages of growth of the aerial parts was shown, and there was 

 also a stimulated growth of the normal (underground) roots of 

 wheat and barley in presence of concentrations of this order of 

 magnitude. 



Grace (1938 b) has shown that at least two synthetic growth- 

 substances are compatible with, and stable in, formalin solu- 

 tion. A formalin treatment is widely used in Canada and 

 elsewhere for the repression of that fungal condition in cereals 

 known as smut. Smutted seeds treated by formalin have re- 

 duced germination (some of the seeds being dead) and the 

 survivors have a weakened growth. According to Grace, such 

 damage to seed oats and wheat can be considerably reduced, or 

 entirely offset, by adding minute amounts of a-naphthyl or 

 3-indole acetic acid to the formalin solution before it is used 

 on the seed. The strengths recommended were o-oi-i part 

 per million of solution. Such a mixture of formalin and 

 growth-substance can be stored at least ten weeks. It is 

 thought that the effect on the seed of the mixture of formalin 

 and growth-substance should be attributed to stimulation of 

 damaged embryos, rather than to prevention of damage at the 

 time of treatment. It might seem that the artificial growth- 

 substance replaces some natural hormone inactivated by the 

 treatment, but there is evidence that the benefit cannot be so 

 simply explained. 



A demonstration of "the undoubted physiological activity" 

 on winter wheat of mercurial dusts containing about 2-10 

 parts per million of the indole- and a-naphthyl-acetic acid 

 was made by McRostie and others (1938). The dusts were 

 applied to the seed, the comparison being between treatment 

 with mercurial fungicide alone and fungicide plus growth- 

 substances. Small but significant increases of yield of both 

 grain and straw were reported, but the experiment is regarded 

 as preliminary, and further work must be done to define the 

 effects of variety, season, and other variables. This was the 

 first field experiment with growth-substances applied to an 

 agricultural crop. 



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