42 
Journal of Agricultural Research 
Vol. XXIV, No. I 
concen^ation of 125 parts per million is just about the concentration 
producing the best growth under these conditions, as shown by other 
work; and as will be seen later, there was very little likelihood of the 
plant absorbing very much more plant food than was actually needed for 
its development. 
Beginning with the fifth day after the seeds were placed in the solution, 
on every third day enough plants for an analysis were drawn from the 
pans, care being taken to draw some plants from each pan to equalize 
variations in the cultures as much as possible. When one of the culture 
pans fell below the normal it was discarded. In this way a representative 
set of plants could be withdrawn each time. The analyses of the plants, 
together with that of the original seeds, are shown in Table I, the results 
being expressed on the basis of 100 plants. 
Table I .—Analyses of 100 wheat seedlings, grown in nutrient solutions, at different 
stages of growth 
No. 
Stage of growth. 
Dry weight. 
N 
KsO 
P20i 
I 
Original seeds. 
Gm, 
2. 14 
Gm. 
0. 0490 
Gm. 
0. 0295 
Gm. 
0. 0210 
2 
5 days old. 
I. 89 
• 0565 
. 0272 
. 0184 
3 
8 days old. 
2. 05 
.0742 
. 0489 
.0250 
4 
II days old. 
I. 82 
. 0812 
. 0869 
. 0308 
5 
14 days old. 
I- 95 
.0924 
. 1203 
.0336 
6 
17 days old.. 
2. 30 
. 1160 
. 1311 
.0570 
7 
20 days old. 
3 - 04 
. 1410 
. 1466 
.0740 
8 
23 days old. 
3 - 50 
. 1946 
; 1610 
. 1020 
9 
26 days old. 
4. 64 
. 2110 
. 2018 
. 1220 
It will be noticed that there is a falling off in dry weight, in potash, and 
in phosphoric acid, but not in nitrogen, up to the fifth day. The loss in 
weight is, of course, due largely to the decomposition of starch and sugar 
of the seeds and to the evolution of carbon dioxid. This loss often 
amounts to as much as 40 per cent of the dry weight before enough 
plant food and carbon dioxid are absorbed to balance the loss. Many 
experimenters with wheat seedlings, when using dry weight as a crite¬ 
rion, fail to realize the fact that in the first stage of growth they are 
dealing with a diminishing quantity. The loss of potash and phos¬ 
phoric acid always takes place at the beginning of germination, due to 
the exudation of these plant foods from the seed. It might be added 
that these very salts that are exuded from the seeds are absorbed by 
the seedling in a few days or as soon as the radicle has become suffi¬ 
ciently developed. There is usually little exudation of nitrogen for the 
reason that the nitrogen of the seed exists in organic combinations, pro¬ 
tein, and is not readily dissolved out by water. 
These results when plotted are represented by figure i. 
By cutting the curves through any particular date it seems possible 
to determine the relative demand of the plant at that age for the three 
important plant foods. It is also evident that the relative demand for 
food changes very rapidly as the plant develops. Beginning about the 
fifth day, when the plants begin to feed, the curve for potash rises very 
rapidly. The little seedling awakes to life with a ravenous appetite for 
potash, out of proportion to other plant foods. When the seeds are 
moistened and warmed preparatory for germination, the potash which 
