ACTION OF ALPHA-CROTONIC ACID ON PLANTS 177 
triangle i-i 6-21, figure 2; the mainly nitrogenous, subtriangle 21-61-66, 
and the mainly potassic solutions, subtriangle 56-16-61. In the 21 cultures 
high in phosphate growth was reduced by the crotonic acid 5 percent, in 
the mainly nitrogenous cultures growth was reduced 25 percent, and in the 
mainly potassic, 28 percent. 
Twelve of the cultures from these two sets are shown in figure 8; cultures 
I and lA contain nitrogen and potash but no phosphate. The cultures 
marked "A" contain 25 parts per million of crotonic acid. Here it is seen 
that the crotonic acid has reduced growth considerably. This is also true 
in cultures 2 and 2A, which contain only 8 parts per million of P2O5. In 
cultures 3 and 3A, which contain 24 parts per million P2O5, growth is re- 
duced only slightly, the roots being checked more than the tops. In the 
other three sets of cultures, nos. 4, 5, and 6, growth of both tops and roots 
is about as good in the crotonic acid as in the normal solution. Culture 4 
contains 40 parts per million P2O5; culture 5, 56, and culture 6, 72 parts 
per million P2O5. 
Effect of Tri-sodium Phosphate 
In the entire set of cultures in which the tri-sodium phosphate (Na3P04) 
was used with sodium nitrate and potassium sulphate, the harmfulness of 
the crotonic acid was relatively less than in the former experiments. How- 
Fig. 9. Green weight in grams of wheat plants in nutrient solutions containing varying 
ratios of phosphate, nitrate, and potash, the source of P2O5 being tri-sodium phosphate, 
(i) Without crotonic acid, and (2) with 25 p. p.m. crotonic acid. 
ever, it is seen by examining the charts of figure 9 and table 6 that in the 
solutions which contained none or only a small amount of phosphate, the 
crotonic acid had much more effect than in solutions containing a higher 
amount of this element. In fact, where as much as 64 parts per million of 
phosphate were used growth was larger in the cultures containing crotonic 
acid. The effect of the organic acid was more severe in the line of cultures 
containing no phosphate. 
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