小麦体细胞胚发生的超微结构研究

ULTRASTRUCTURAL STUDIES OF SOMATIC EMBRYOGENESIS IN WHEAT

对小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）幼胚培养中体细胞胚发生过程的超微结构变化进行了研究，结果如下：（１）原体细胞中大液泡消失，存在大量小液泡，细胞质的电子密度加强，核大，核仁明显，出现多核仁；（２）细胞器数量和种类，如质体、核糖体和线粒体增加；（３）细胞壁加厚，胞间连丝逐渐消失，细胞器数量丰富，胚性细胞中积累淀粉；（４）细胞壁加厚的胚性细胞中存在核仁液泡、自体吞噬泡和分泌泡；（５）多细胞原胚、球形胚和梨形胚被一层外壁包围，但胚体内细胞间广泛存在胞间连丝；（６）成熟胚生长点部位的细胞内质体中出现膜系结构，已向叶绿体转变。

Electron microscopic observation of somatic embryogenesis from cultured immature wheat embryos revealed the presence of a lot of small vacuoles, a large nucleus, clear nucleolus and polynucleoli.The electron density of cytoplasm was strengthened during somatic embryogenesis. Quantity and type of organelles——plastid, ribosome and mitochondrion were increased; thickened cell wall, disappeared plasmodesmata, increased organelles and starch accumulation in the embryogenic cells. Nucleolus vacuoles, autophagic vacuoles and secretory vesicles were present in the embryogenic cells with thickened cell walls. The multicellular proembryos, globular embryoid and pear shaped embryoid were surrounded by an envelop, but plasmodesmata existed extensively between cells of somatic embryoid. The membranous structures appeared in the plastid which underwent transformation into chloroplast in the cells of growing point in almost mature embryoid. The relation of the above mentioned structural changes to somatic embryogenesis is also discussed.