Morphogenetic Alterations of Spikelets on a Straighthead Panicle in Rice

[摘要] A study was undertaken to clarify microscopically the characteristics of morphogenetic alterations in rice spikelets on a straighthead panicle. Plants of an upland rice (Oryza sativa L. cv. H4) were grown by the method "Onae Ishokuho" developed by Matsuo et al. to induce straighthead symptoms. Spikelets fixed with Formaline-acetic acid-alcohol at heading time were dissected under a stereo microscope to investigate morphogenetic changes of sexual organs, the pistil and stamens, and glumes. Some of the spikelets having principal changes were examined by scanning electron microscope (SEM). Of the total 407 spikelets dissected, 93.9% lacked in both sexual organs and 18.9% developed spikelet-type (S-type) proliferation, in which instead of normal sexual organs small spikelet (s) differentiated. A small protuberance viewed by stereo microscope at the site of pistil was identitied by SENI to be the same as normal spikelet primordium. Of the total spikelets, 3.7% developed pistil hyperplasia to have differentiated more stigma (ta) or pistil (s) than the usual number. Almost all of the spikelets changed the shape of their lemma and palea, and in 40.0% of the total spikelets the palea developed. On the other hand, glumes were increased in 11.5% of spikelets. Spikelets lacking in sexual organs were considered to have possibility to develop any kind of proliferation. It was concluded that initiation of pistil hyperplasia and S-type proliferation were main characteristics in morphogenetic changes of sexual organs induced by straighthead in the present study. Similarity of the changes with other morphogenetic changes by different environmental stresses and its significance were discussed from the view point of spikelet morphogenesis and vegetative proliferation.

[学科分类] 农业科学（综合）

[关键词] Morphogenesis;青立ち症;Pistil hyperplasia;イネ;Proliferation;貫生;Rice;形態形成;Scanning electron microscope (SEM);小穂;Spikelet;雌ずい増生;straighthead;走査電子顕微鏡