i8o 
J. J. SKINNER AND F. R. REID 
Summary 
Alpha-crotonic acid in amounts of 25 and 50 parts per milli^ yas found 
to be very harmful to wheat plants grown in nutrient culture solutions. 
'The solutions were composed of calcium acid phosphate, sodium nitrate, 
and potassium sulphate, and were prepared according to the triangular 
system. Growth was reduced about 50 percent when the crotonic acid was 
used in amounts of 50 parts per million and 35 percent in concentration of 
25 parts per million. 
Phosphates had an ameliorating effect on the harmfulness of crotonic 
acid. Where large amounts of P2O5 were present in the nutrient solution, 
the effect of the crotonic acid was milder than in those solutions which 
contained a smaller amount of P2O5. The toxic action of the organic com- 
pound in nutrient solutions decreased as the content of P2O5 increased. 
Experiments using NaH2P04, Na2HP04, and Na3P04 in the place of CaH4 
(P04)2, showed that each of these phosphate salts, regardless of the basic 
or acidic character of the salt, had an action antagonistic to the harmfulness 
of alpha-crotonic acid, which seems to show that the antagonistic action of 
the phosphate salts toward crotonic acid is due to the phosphate radical. 
It is also shown that the effect of crotonic acid is less severe in solutions 
containing alkaline salts. 
Soil Fertility Investigations, 
Bureau of Plant Industry, 
Washington, D. C. 
