STUDIES ON INTERNODE ELONGATION IN SOYBEAN PLANTS .2. EFFECTS OF MECHANICAL STIMULATION ON INTERNODE ELONGATION

In order to clarify the effects of physical stress on the internode elongation of soybean (Glycine max Merr. cv. Fukuyutaka), mechanical stimulation was given to pot-grown plants by stroking upper part of shoot with a dusting brush continuously for 15 to 180 seconds per day during certain period of different growth stages. The mechanical stimulation inhibited the internode elongation on the main stem, but did not affect yield characters (Table 2). The inhibition was limited on the upper elongating internode subjected to stimulation and was more when treated during the period from floral differentiation to the beginning of flowering stage (Table 2 and Fig. 1-A). As the longer the stimulating time was, the more the internode elongation was depressed (Fig. 2). When the mechanical stimulation was given to one of the two same-sized branches emerged from the cotyledonary nodes on the Y-shaped plant which was forced to form by removing apical shoot above the nodes, the inhibition of internode elongation occurred on the stroked branch but not on the other branch, suggesting that the stimulus was not transmitted from a treated to an untreated branch. From these results, the main stem elongation of soybean could be reduced by the mechanical stimulation without affecting reproductive characters including seed yield. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.