水稻小穗轴的结构及其在开闭颖过程中的变化

STRUCTURE OF RACHILLAE AND ITS CHANGES OURING FLOWER OPENING AND CLOSURE IN RICE

用光学显微镜和电子显微镜观察了水稻小穗轴的维管结构及其在开闭颖过程中的变化。结果表明。（１）水稻小穗轴是由表皮、皮层厚壁细胞和维管束系统组成。来自小枝梗的１条大维管束和数条小维管束合并后进入小穗轴，向四周分散，韧皮部朝外，木质部在内，并分段结合，先后分枝出通外颖５条，通内颖３条，通浆片４条，通花丝６条，通雌蕊３条等维管束。通向内外颖的维管束为有限外韧型，维管束中薄壁细胞大量低，而通向浆片和雌雄总的维管束木质部和韧皮部相互嵌合，继管束中薄壁细胞含量高。（２）通雌雄蕊的维管束的筛管不仅在端壁上有筛扎，而且在侧壁上也有筛孔，筛孔中充满了胼胝质，筛管中富含只有蛋白质结晶体的Ｐ－质体，筛管周围的薄壁细胞中的线粒体密度很高，并含有许多小液泡。（３）小穗轴中有两类厚壁细胞，一类是皮层厚壁细胞，形似花生状；另一类分布在维管束间和维管束周围，两类厚壁细胞部有较多的纹孔，纹几中充满胞间连丝，厚壁细胞间隙较大，能进行共质体和质外体的运输。厚壁细胞中含有只有片层结构、能进行淀粉代谢的质体。开颖前，质体中通常见不到淀粉粒，闭颖后，质体中大量合成和积累淀粉。（４）开颖后浆片、花丝和柱头细胞发生自溶，分解物通过导管进入小穗轴，在开花后１?

The strueture of vascular bundles of rachillae and its changes during flower opening andclosure in rice were observed with microscopes and an elcetron microseope. The results were as follows:(1)Arice rachilla was composed of cpidermis, thick-walled cells of cortices and a vascular system. Beingmerged and got into the rachilla, one large and .several small vascular bundles from pedicels separatedaround with their phloem external, xylem internal and combined by segments, and more vascular bundleswere further branched:5 of them went through to a lemma, 3 to a palca,4 to loducles, 6 to filaments and 3to pistil. The vascular bundles through to the palea and lemma were limited collateral types and had fewerparenchyma cells. But the bundles to the lodicule, pistil and stamen had more parenehyma cells and theirxylem and phlocm were mosaiccd cach other.(2) The sicvc pores filled up with callosc not only existed onthe tip walls but also on the side walls of the sicves tubes of the vascular bundles through to pistils andstamens. There were rich p-type plastids with protein crystillization in the sieves tubes. The parenchymacclls around the tubes had many mitochordria and small vacuolcs.(3) There were two kinds of thich-wal-led cells in the rachilla. One was the cortex thick walled cells, liked peanut. The other distributed among oraround vascular bundles. Both of them had many pits filled up with plasmodesmata. The intereellularspace between thick-walled cells was large and could transport via symplast and apoplast; The thick-wal- led cells contained lammellar-structured plastids in which the starch metabolism could be taken place. Agreat number of starch grains were synthesised and accumulated in plastids after flower closure,they couldnot be found before flowering.(4) The cells of lodiculcs,filaments and pistil could antolysed after flow. ering, and their catabolites were transfered to rachilla via tracheae. The tracheac to the lodicuks, filamentand pistil and the interccllar spaces were filled up with these catabolites one-two day after flowering.