Apr. i, 192 
Effect of Time of Irrigation on Kernel Development 
45 
losing color. The plants on plot 3 had exhausted their water supply to 
the point of wilting badly. Those on plot 4 were affected slightly. This 
is apparent in the various graphs, but is more significant when correlated 
with the field observation. 
The ripening was not uniform. On most of the plots the bases of the 
spikes were inclosed in the leaf sheaths. The kernels so inclosed did not 
ripen as soon as those which were exposed. The kernels from plot 8 
were wrinkling by August 5 and therefore were ripe. The tip kernels 
from all plots were wrinkling by August 8, but the basal kernels in some 
cases were still adding material. Of the plots irrigated once after June 
23, plot 5 was the last to ripen, having sufficient water and having been 
irrigated before maturity was as far advanced as in plot 7. The later 
maturity of plot 5 is apparent in figure 18. 
The departure in the growth of the various plots came at about the 
critical stage pointed out in the paper on daily development—that is, 14 
days after flowering. The course of the wet weights indicated that the 
ultimate size of the kernel was affected 3 days earlier. The nature of 
this change has not been investigated; but, as was suggested, it may be 
correlated with the stopping of the addition of new cells or with the enter¬ 
ing upon the secondary phase of starch formation. 
At Aberdeen, the deposit of dry matter continues until just before the 
grain wrinkles. Maturity at Aberdeen seems to occur at the earliest 
date possible without accident or drying. In other words, there is no 
prolonged period of maturation such as apparently takes place in districts 
where cold, wet weather occurs at ripening time. 
CONCLUSIONS 
At Aberdeen, Idaho, deposit of dry matter in the kernel continues 
until very near the point of absolute ripeness. 
The plants are able to utilize water up to the date of full maturity. 
Late irrigation results in a greater activity and a later maturity. 
A deficiency of water, even after the spikes are losing their color, 
results in checking the deposit of dry matter. 
A deficiency of water earlier in the development of the kernel probably 
determines the size of the kernel, even before the rate of deposit of dry 
matter is checked. 
