摘要
通过透射电镜对水稻（ＯｒｙｚａｓａｔｉｖａＬ．）胚囊卵器发育过程中超微结构的变化进行观察，结果表明：卵器刚形成时，３个细胞均有完整的细胞壁，壁上分布着许多胞间连丝，不久各细胞合点极壁出现突起解体。随着卵器细胞进一步发育，合点极壁不断解体。到胚囊成熟时，卵细胞的合点极壁消失，仅留下一层质膜；助细胞由于出现退化，侧边近合点端壁出现断裂破碎解体。此时，３个细胞只在弯钩壁上观察到胞间连丝。卵器细胞不同发育阶段各种细胞器的变化很明显，其中最为明显的是质体和液泡。卵细胞在整个发育过程中大部分的质体都含有淀粉粒，而助细胞的质体在２个极核移向卵器上方时，质体内淀粉粒已消失，直至胚囊成熟也未重新出现；卵细胞液泡的出现时间、大小和位置与助细胞的有所不同，卵细胞液泡出现较迟，但到发育后期，液泡体积却明显比助细胞的大，液泡除了主要位于合点极外，珠孔极也有些液泡，而助细胞的则主要位于合点极。助细胞中脂滴的出现存在一个高峰期，即发生在胚囊近成熟时。助细胞核在发育早期呈椭圆形，位于近中部偏珠孔端，在发育中后期呈不规则形，位于近珠孔端壁旁边。水稻卵器发育过程中各细胞的超微结构变化充分反映其代谢规律。
The development of the eggapparatus (consisted of an egg cell and two synergids) of rice (Oryza sativa L.) was studied at the ultrastructural level.The walls of the egg cell and synergids,immediately after their formation, possessed numerous plasmodesmata.Plasmodesmata were also present on walls between the egg cell and synergids.During the enlargement phase of the egg cell and synergids,the walls at the tip region began to loosen and vesiculate.By the time the embryo sac became mature,the part of the wall of the egg cell and synergids,facing the chalaza,disappeared.Consequently,the tip regions of the egg cell and synergids were only protected by a plasma membrane.When the embryo sac reached full maturity,the upper and middle region of the wall of the synergids broke up into pieces.At that time one synergid began to degenerate.Plasmodesmata persisted at the hook region of the wall of both the egg cell and synergids.Most plastids in the egg cell contained starch grains that persisted throughout the period of the embryo sac development.Starch grains in the plastids of the synergids appeared only before the time when the two polarnuclei moved into the region above the eggapparatus.They then disappeared and did not appear again until the embryo sac had reached full maturity.The size and location of the vacuoles in the egg cell were different from those in the synergids.The time of formation was also different.Vacuoles in the egg cell formed late in comparison with the synergids.Vacuoles in the chalazal region of the egg cell (especially at the early stage of the embryo sac development) were much larger than those in the micropylar region.Vacuoles in the synergids tended to concentrate mainly in the chalazal region.There was a peak period of lipid formation in the two synergids.The peak appeared when the embryo sac neared maturity.At the early stage of development,the nuclei of the synergids were elliptical in shape and were situated at the central region near the micropyle.The shape of the nuclei at the lat
基金
香港RGC部分资助
关键词
水稻
胚囊
卵器
受精前
超微结构
Rice, Embryo sac, Eggapparatus, Prefertilization, Ultrastructure
