180 BOTANICAL GAZETTE [SEPTEMBER 
This general relationship is even more strongly shown when the 
decreases in the concentrations of the solutions in these various 
groups are considered. The average decrease, in solutions with 
and without dihydroxystearic acid, for each group in each experi- 
ment, is shown in table II. 
TABLE II 
SHOWING THE AVERAGE DECREASES IN THE CONCENTRATION OF TOTAL CONSTITUENTS 
IN THE GROUP OF CULTURE SOLUTIONS CONTAINING FERTILIZER SALTS HAVING 
THE COMPOSITION OF 50 TO 100 PER CENT OF ANY ONE OF THE COMPONENTS P.0s, 
NH,, AND K.O, WITHOUT AND WITH DIHYDROXYSTEARIC ACID (ORIGINAL CONCEN- 
TRATION =80 PARTS PER MILLION). 
50 100 PER CENT P,O, 50-I00 PER CENT NH; 50-100 PER CENT K,O 
ae 
Decrease Decrease z er 
in in a 
m " droxy 
: dihydroxy- ‘ dihydroxy- ay i dihydro 
ExpeRIMENT oe With | stearic —— With | stearic buat With genre 
aci no aci Jutions 
solutions. solutions. “No 1 
ormal Normal equals 100 
equals oo equals 100 Danson 
ee ce 27.8 | 37.6 63 35-4 | 24.0 68 34-0 | 13-9 ‘ 
CS a eo 28.9 | 24.6 55 30.3 | 34.6 114 38.5 | 30-8 69 
Pca See 27.8) 23.8 8 -9- : 8 .O | 31.0 
3 Z 3 5 35-9 | 32.0 9 45 a cee 
The third column under each fertilizer group gives the relation 
between these decreases, the decrease in concentration when 
dibydroxystearic acid is absent being considered as the normal 
for comparison and equal to too. A comparison of these relative 
effects shows that the mainly nitrogenous fertilizers give the highest 
results. In other words, the decrease with the nitrogenous ferti- 
lizers was more nearly like that observed under the normal con- 
ditions where dihydroxystearic acid was absent. This result a 
be interpreted to mean that the mainly nitrogenous fertilizers 
decreased the inhibitive effect of the dihydroxystearic #0" 
although it does not show whether this is a direct or an IN@"™ 
effect; that is, whether there is an actual decrease of this inhibitive 
material or whether there is mainly the ability of the plant t0 
withstand the attacks under these conditions. Attention es 
already been called to the fact that this substance when in ate 
most easily destroyed by processes which promote oxidation, & 
it should be borne in mind that the mainly nitrogenous fertilizers 
are the ones which promote the most active root oxidation by the 
plants themselves. A study of the oxidation of roots in these : a 
Aart atiee: i 
pA cS OG ee A a or eS. 
d 
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