水稻反足细胞发育期间超微结构变化的观察

An Ultrastructural Study on the Development of Antipodal Cells in Rice Embryo Sac

本文通过透射电镜对水稻反足细胞形成发育过程中超微结构的变化进行观察。结果表明,反足细胞发育过程中细胞壁、细胞核和各种细胞器均出现明显的变化。在发育早期(即胚囊中两个极核移向卵器上方之前的时期),反足细胞位于胚囊合点端顶部,细胞间的壁很完整。反足细胞与珠心细胞相邻的壁(即最顶部的胚囊壁)、反足细胞彼此之间的壁,以及反足细胞与中央细胞相邻的壁上均有胞间连丝分布;在发育中后期(即胚囊中两个极核移向卵器上方及以后的时期),原有的壁加厚,新壁不断形成。除了新壁产生的个别胞间连丝外,已有壁上的胞间连丝均消失。反足细胞的核在发育早期多为球形,中后期则经常形成“珊瑚状”。反足细胞的各种细胞器中,在整个发育过程中数量一直保持较高水平的有核糖体、线粒体和内质网。高尔基体形态变化较特别,在中后期出现“念珠状”的潴泡。质体在发育早期含有淀粉粒,中后期淀粉粒消失。大型液泡发生在发育早期,但以后则消失。到胚囊成熟时,反足细胞的液泡很小,且为数不多。水稻反足细胞发育过程中超微结构的变化规律可能反映反足细胞在胚囊发育过程中功能的变化。

An uhrastructural study on antipodal development was carried out in rice. The results showed that the ultrastructure of walls, nuclei and various organella underwent considerable changes during antipodal development. At the early stage, each antipodal cell was surrounded by a thin layer of wall. Plasmodesmata were present in the walls between the chalazal antipodal and the nucellar cell, in between the antipodals and the walls between the micropylar antipodal and the central cell. At mid and late stage, the original walls of the antipodal cell be came much thickened and some new walls formed. At the late stage of embryo sac development, all plasmodesmata disappeared from the original wall. Few plasmodesmata were, however, still seen present in some of the newly formed walls. Nuclei of antipodal were round in shape at early stage. However, some of them became'coral-shaped' at mid and late stages. The cytoplasm of the antipodals contained numerous ribosomes, mitochondria and endoplasmic reticulum. The shape of dictyosomes was quite variable and they became'bead-shaped' at the mid and late stage. Plastids contained starch grains at early and mid stage, which disappeared at mid and late stage. Large vacuoles were present in the early stage. They disappeared at mid and late stages. At the time of embryo sac maturity, only a few small vacuoles could be found. The changes of the antipodals seen at the ultrastructural level seemed to suggest that the antipodals might played an active role(e. g. in the supply of nutrients to the embryo sac) in the development of the embryo sac.