Nov. 15, 1925 
Growth-Equation Constants in Crop Studies 
981 
organs directly associated with seed development, but included in 
the stalk data. For the sunflower this would be the head except the 
seed, and for the corn the husk and shank. Fortunately some data 
are available in the case of corn showing the proportion of crude fiber 
in the husk and the remainder of the stalk. Schweitzer 10 gives data 
which indicate that 19 per cent of the crude fiber of the stalk 138 days 
after planting was in the husk. Grindley * 11 found in a crop of corn 
yielding 100 bushels per acre that 18 per cent of the crude fiber of the 
stalk was in the husk and silk. According to the equations of Figure 
5, at 133 days after planting the second cycle is responsible for 24.8 
per cent of the crude fiber of the stalk. Bearing in mind that the 
shank is not included in the proportions of 19 and 18 per cent, as 
estimated from Schweitzer’s and Grindley’s figures, the proportions 
suggested in Figure 5 from the theoretical treatment of the combined 
data are consistent with the view that the second growth cycle 
indicated by the stalk data is quite directly associated with seed 
development. 
GROWTH IN SEED AND EAR 
The data j ust examined indicate that growth in the sunflower and 
corn crops occurs in two cycles, that the first cycle is associated with 
the vegetative functions and the second with the reproductive func¬ 
tions. In agreement with this, the development of seed and ear seems 
to constitute a well defined growth cycle, which, however, in the case 
of certain constituents is not completed at the death of the stalk. 
The writers’ data on the sunflower seed show that all of the constitu¬ 
ents except nitrogen-free extract continued to increase in substantial 
conformity with the autocatalytic formula. This is in contrast with 
the behavior of the same constituents of the stalk. In the stalk there 
is first an accumulation and then a loss in the case of all constituents 
except crude fiber and aluminum. This loss may be regarded as due 
to a process of senescence, the reverse of growth. 
Properly, one might regard the development of the seed as cycle 
one, and accordingly A of the seed growth equations is to be divided 
by the number of seeds per acre to convert the equation to an individ¬ 
ual basis. Another growth cycle then ensues at that later time 
when the seed is provided with the conditions for germination and 
growth. This cycle also conforms to the autocatalytic formula with 
reference to the essentially structural materials. With reference to 
other materials, however, the processes of senescence predominate 
over those of growth after a time, so that the equation used is not 
alone adequate to describe the entire changes. 
Robertson 12 has analyzed data of Monnier on the growth of the oats 
plant and has reached the conclusion that the mineral constituents 
did not follow the autocatalytic law of growth. Considering the 
sunflower crop as a whole, the writers’ data would require the same 
conclusion with reference not only to the mineral constituents but 
also to all the other constituents, except crude fiber, crude fat, and 
aluminum. This condition is due, however, to the senile losses in 
10 Schweitzer, P. study of the life history of corn at its different periods of growth. Mo. 
Agr. Exp. Sta. Bui. 9, 78 p. 1889. 
11 Unpublished data, Ill. Agr. Exp. Sta. 
12 Robertson, T. B. the chemical basis of growth and senescence. 389 p., illus. Philadelphia 
and London. 1923. 
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