イネ小穂の貫性化に関する研究 : 第4報 貫性化小穂における組織・器官形成 (その1)

抄録

This experiment was carried out to make clear whether the apical meristems in the proliferated spikelet primordia of the mutant strain induced by X-ray irradiation were different or not in size and organization with those of normal ones at the differentiation stage of stamen primordia, and whether, the vascularization of "spikelet-like organ" was the same or not as normal spikelets. The apical meristems of young proliferated spikelets, differentiating glumes or spikelet-like organ(s) successively, indicated larger values both in height and bottom dianmeter, especially in height, than those of normal ones, and the ratio of height to diameter (H/D ratio), therefore, were larger in the proliferated spikelets than in normal ones. The structure of the apical meristems in the proliferated spikelets had considerably definite organization composed of initial cell(s), rib meristem and peripheral meristem, though the smaller apical meristems (diameter: below 50 μ, H/D ratio: below 0.5) had one layer of tunica and indefinitely organized corpus. These shoot apices had a tendency to elongate remarkably, differentiating some organ primordia at the subapical region of them. The differentiation and connection of provascular bundles in the spikelet-like organ was confirmed to be the same as the normal spikelets histogenetically. Judging from the facts that the proliferated spikelets have larger and more protuberant apical meristems and successively differentiate spikelet(s) or glumes, it is evident that the shoot apices of the proliferated spikelets have prominent mitotic activity, especially in corpus, and continue the vegetative growth which differentiate branches or leafy organs, retarding the transition into the reproductive stage. The phenomenon which one or more spikelet primordia are differentiated in a spikelet is considered to indicate that the apical meristem of the proliferated spikelet has regained the morphogenetic character of previously passed developmental stage, and a rejuvenation or a kind of de-differentiation has occurred in the shoot apex of it. If we can make progress the physiological and genetical studies on the development of these proliferated spikelets, we might be able to contribute to clarify the mechanism of morphogenesis of normal spikelets, especially that of the transition from vegetative growth into the reproductive one, sporogenesis in rice plant.