178 
J. J. SKINNER AND F. R. REID 
Table 6 
Showing the influence of the phosphate in overcoming the harmful effect of a-crotonic acid. 
Green weight of wheat plants in nutrient solutions, composed of Na3P04, 
NaNOs, and K2SO4. Cultures arranged according to content of P2O5. 
Cultures No. 
Parts per Million P2O5 
Average Green Weight of Culture 
Percentage Increase 
or Decrease in 
Crotonic Acid 
(See Fig 2) 
in Nutrient Solution 
Without Crotonic 
With 25 P. p.m. 
Acid 
Crotonic Acid 
grams 
grams 
I 
80 
1.96 
2.18 
+ 11 
2- 3 
72 
2.58 
3-04 
+ 18 
4- 6 
64 
2.99 
3.29 
+ 11 
7-10 
56 
3-37 
3-09 
- 9 
11-15 
48 
3-79 
3-50 
- 8 
16-21 
40 
3-57 
3-50 
— 2 
22-28 
32 
4.06 
3-69 
- 3 
29-36 
24 
4.10 
3.80 
- 7 
37-45 
16 
4-31 
4-15 
- 4 
46-55 
8 
4.29 
3-93 
- 9 
56-66 
0 
3-87 
3-34 
— ID 
When the cultures are grouped, as discussed in the former set, the 21 
mainly phosphate cultures were reduced in growth only 2 percent by the 
crotonic acid, the 21 mainly nitrogenous were reduced in growth 8 percent, 
and the mainly potassic cultures were reduced 6 percent. 
Discussion 
The data presented in connection with the foregoing experiments are 
interesting in that they again show that the physiological effect of organic 
compounds on plant development and growth are altered by inorganic 
salts. The study of crotonic acid adds knowledge of another organic 
compound to the list of those which have been studied in this laboratory.^ 
Its behavior in regard to the action of phosphates is somewhat like that of 
cumarin,^ and of certain of the aldehydes.'' Cumarin is harmful to plants, 
having a characteristic effect, producing stunted tops and distorted leaves. 
Like crotonic acid these effects are overcome or greatly lessened by phos- 
phates. The harmful effect of salicylic and certain of the other aldehydes is 
also influenced by phosphates. In soil this compound is oxidized or other- 
wise destroyed by phosphate fertilization. It is also interesting to note 
that the harmful effects of other compounds are influenced by nitrogen, and 
those of still others by potash.^ 
^ Schreiner O., and Skinner J. J. Nitrogenous soil constituents and their bearing on 
soil fertility. U. S. Dept. Agr. Bur. Soils, Bull. 87. 1912. 
^ Schreiner, O., and Skinner, J. J. The toxic action of organic compounds as modified 
by fertilizer salts. Bot. Gaz. 54: 31. 1912. Skinner J. J. Influence of phosphates on 
the toxic action of cumarin. Bot. Gaz. 54: 245. 1912. 
^ Schreiner, O., and Skinner, J. J. Harmful effects of aldehydes in soils. U. S. Dept. 
Agr. Bull. 108. 1914. Skinner, J. J. Field test with a toxic soil constituent: Vanillin. 
U. S. Dept. Agr. Bull. 164. 1915. Skinner, J. J. Soil aldehydes. A scientific study of 
a new class of soil constituents unfavorable to crops, their occurrence, properties and 
eWmination in practical agriculture. Journ. Franklin Inst. 186: 165. 1918. 
