46 
Journal of Agricultural Research 
Vol. XXIV, No. I 
The abrupt rise of the potash curve is noticeable, showing the demand 
for potash in the seedling was out of proportion to that for other plant 
foods. The cumulative demand, brought out in this experiment, seems 
to be true, not only for fractional parts of the day but for much longer 
periods. 
DEMAND OF WHEAT PLANTS AFTER BEING-HELD IN DISTILLED 
WATER FROM 2 TO 17 DAYS 
Seven culture pans of soft wheat were germinated and grown in dis¬ 
tilled water for 4 days. One pan was then transferred to a nutrient solu¬ 
tion of 125 parts per million each, nitrogen (N), potash (KjO), and 
phosphoric acid (P2O5), while all the others were kept in distilled 
water. At the end of 3 more days a second pan was placed in the nutrient 
solution, and this process continued every 3 days until six of the lots had 
been taken from distilled water and placed in nutrient solution. They 
were then allowed to grow for 2 more days, when they were taken down 
and analyzed. Thus the first pan had been feeding from a good nutri¬ 
ent solution for 17 days, while the last pan had been feeding only 2 days. 
The last pan having been grown in distilled water for 15 days had no 
increase in growth over the control when placed in the nutrient solu¬ 
tion. The results of the analyses are shown in Table III. 
Tabi,® III.— Analyses of 100 wheat seedlings grown two or more days in nutrient solutions 
Na 
Days in nutrient solutions. 
Dry weight. 
N 
K2O 
P2O5 
Gm. 
Gm. 
Gm. 
Gm. 
I 
Control 0. 
6. 28 
0. 0840 
0. 0613 
0. 0400 
2 
2. 
6. 60 
. 1410 
. 1154 
.0587 
3 
5 .■.. 
6. $2 
. 1904 
.1685 
.0750 
4 
8. 
7. 12 
. 2268 
. 2090 
.0813 
5 
II. 
6. 80 
. 2674 
•2350 
• 0973 
6 
14. 
6. 80 
. 2604 
. 2361 
. 0908 
7 
17. 
7. 00 
. 2912 
. 2580 
. 1440 
It will be seen by refemng to Table III that with each plant food 
element the absorption for the 2-day period was out of proportion to 
that of the 17-day period. By subtracting the quantity of potash in 
the control, for example, from that of the plants grown for 2 days in 
the nutrient solution, we get 0.0541 gm. of potash actually absorbed 
in 2 days. In like manner, by subtracting the control from the 17- 
day plants, we get only 0.1967 gm. potash actually absorbed in 17 days, 
when we should get 0.459 gm. of potash if time alone governed absorp¬ 
tion. These results plot very well, showing that the demand is fairly 
regular and cumulative. This experiment was repeated, changing the 
plants in 2-day periods, with similar results. 
If Tables IV and V, showing the rates of absorption of the different 
plant foods, are studied, other interesting relations are brought out. 
From Table IV it appears that the absorption of potash for the short 
period is much more pronounced than the absorption of other plant 
foods. On the other hand, when seedlings are left in the nutrient solu¬ 
tion for a number of days (Table V), the absorption of potash and 
nitrogen shows a remarkable agreement in the rate. This is brought out 
in figures 4 and 5. 
