Five castor plants of Shanghai local variety of small grain, whose seeds had been produced in Tokyo University of Education at Komaba, were grown with pot culture in a green house in 1973. The growth in length of main stem, every lateral branch and leaf was measured every second day.
The growth of both lateral branches and leaves proceeded according to the manner of growth curve equation known to be same as that of monomolecular autocatalitic reaction; that is, the growth was linear except the later stage, when the length was plotted logarithmically against number of days. The linear portion will be refered to as growth line in this summary.
The growth lines of leaves were arranged in almost parallel with fairly uniform intervals in order of appearance, i, e. from lower to upper leaves. In lateral branches, however, the growth of branches on a mother stem took place almost simultaneously.
The stem parts and 1st leaves (numbered in order of appearance) of branches attained to 10 mm long at nearly the same time as the first flowering of the racemes of their respective mother stems, in case of productive branches. In non-productive branches, mostly 3rd (numbered from top to bottom, see Fig. 1) or lower node branches, on the other hand, the stems and 1st leaves attained to 10 mm long later than the first flowering.
The plastochron indices (refered to as P. I.) of main stems proceeded linearly but very slowly at the begining portion of growth upto about P. I. 0.6, afterwards proceeded also linearly with much larger rate. In case of branches, P. I. increased linearly at rapid and similar rate to that of the later portion of main stems.
As to the growth rate (exprssed by regression coefficient of logarithm length to number of days for the above-mentioned linear portion) and increasing rate of P. I. with temperature effect eliminated, main stems were smaller than lateral branches, furthermore, some differences were observed among branches depending on the order and the position on the mother stem. That is, primary branches had larger growth rate than secondary branches, and the 1st node branches were rapider than 2nd node branches in increasing of P. I. The 3rd or lower node branches, mostly non-productive, had smaller growth rate and P. I. increasing rate than the uppermost two branches. The 1st and 2nd leaves had larger growth rate than 3rd and 4th leaves.
There was little difference in final length between the 1st node and 2nd node branches, both of which were vigorous and mostly productive. The 3rd or lower branches were shorter in final length than the uppermost two branches. Secondary branches were shorter than primary branches. This was probably caused, at least partly, by decrease in number of nodes under the long day condition.
The lower node branches showed larger ratio of logL
u to logL
f (as to L
u and L
f, see Fig. 5), sometimes close to 1. This fact suggested that those lower branches stopped growing during or shortly after the linear stage of active growth.
The comparison of growth including P. I. among branches of different orders and positions are being made about castor plants grown in field under natural condition.
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