Vegetative Proliferations of Floral Spikelets in Oryzasativa L. : III. The external morphology of the proliferations in the spikelets of a mutant strain induced by the treatment of ethylene imine.

Abstract

This experiment was carried out to compare the proliferations in the spikelets of a mutant strain induced by the treatment of ethylene imine with that induced by X-ray irradiation which had been reported previously, and to make clear the common structural tendencies between both proliferations. External morphological phenomena observed in this experiment were as follows; 1) initiation of adventitious roots at the basal portion of spikelets, 2) remarkable elongation and multi-venation of empty glumes, 3) successive initiation of foliage leaves forming a vegetative plantlet, 4) decrease of stamens in number, 5) increase of spikelets in number, etc. Almost of those phenomena mentioned above were the same as the result s induced by X-ray irradiation, and a seedling-like plantlet observed in this experiment were agreed with a "leafy shoot", reported previously, on the point that it was composed of many leafy glumes like a primary leaf of the seedling, arranging 1/2 alternate phy11otaxis. It was made, therefore, clear that those proliferations which have been observed in this experiment were the same phenomena as those of X-ray irradiation in the point of indicating a kind of re-vegetative growth in the tendency of the degenration of reproductive organs. Judging from that the gradual morphological changes of leaves which composed a seedling-like plantlet followed almost the same tendency as seen in the seedling plant, it could be said for certain that the proliferation initiated on the spike in this experiment assumed to follow the same morphogenetic process as in the seedling developed from the the germination of seed. Therefore, the development of the proliferation was considered to be a kind of the transformation from reproductive growth stage (or phase) to vegetative one in the spikelet primordium, showing the capacity to develop into the individual plantlet by means of the initiation of adventitious roots. On the physiological background of the initiation of the proliferation, it was suggested that some changes of the endogenous gibberellin might be participated with the initiation of the proliferation judging from the fact that the number of spikelets in a proliferated panicle revealed the same tendency of increase as in a panicle treated with gibberellic acid.