花生胚乳细胞化的超微结构观察

花生（ＡｒａｃｈｉｓｈｙｐｏｇｅａｅＬ．）心形胚期的胚乳游离核多瓣裂，或具长尾状结构。胚乳细胞质内有大量线粒体、质体、高尔基体、小泡及少量内质网。中央细胞壁有壁内突。球胚及心形胚期常见胚乳瘤。心形胚晚期，胚乳开始细胞化，胚乳细胞壁形成有３种方式，分别存在于不同的胚珠中：（１）从胚囊壁产生自由生长壁形成初始垂周壁，具有明显的电子密度深的中层，其生长主要靠末端的高尔基体小泡及内质网囊泡的融合。两相邻的自由生长壁末端或其分枝末端相连形成胚乳细胞。（２）核有丝分裂后产生细胞板，细胞板向外扩展并可分枝。间期的非姊妹核间也观察到形成了细胞板。小泡与微管参与细胞板的扩展，高尔基体和内质网是小泡的主要来源。细胞板的扩展末端相互连接，形成胚乳细胞的前身。小泡继续加入细胞板的组成，以后形成胚乳细胞壁。（３）胚乳细胞质中，出现一些比较大的不规则形的片段性泡状结构，它们可能来源于高尔基体小泡，这些片段性泡状结构随机相连形成细胞壁，未见微管参与。胚乳细胞外切向壁及经向壁上有壁内突。

AN ULTRASTRUCTURAL OBSERVATION OF ENDOSPERM CELLULARIZATION IN ARACHIS HYPOGEAE

Cellularization of endosperm in peanut was observed with transmission electronmicroscopy.The free nuclei of endosperm at heart-shaped embryo stage are irregular in shape.Abundant mitochondria,plastids,Golgi bodies,vesicles and some endoplasmic reticulum arepresent in the cytoplasm of the free nuclear endosperm. The endosperm nodules are usually foundat globular and heart-shaped embryo stage. There exist wall ingrowths on the embryo sac wall.Three patterns of endospenn cellularization were observed in different ovules:(1)The initialanticlinal walls arise from the em brvo sac wall and grow predominantly by the coalescence ofGolgi vesicles and endoplasmic reticulum cisternae. These freely growing walls which have middlelamellae branch and eventually meet to form the endosperm cells.(2)After the mitosis of thenuclei,the cell plates are formed between the sister nuclei.These cell plates grow continuously andbranch.The cell plates are observed between the nonsister nuclei too,They are growing withvesicles and microtubules,the vesicles come from Golgi bodies and endoplasmic reticulum. ThecelI plates joIn each other to form the precursors of the endosperm cells. Numerous vesicle continue to fuse with the cell plates and form the walls of endosperm cells later.(3) There are many irregular shaped discontinuous vesiculous structures in the cytoplasm of endosperm, which may be formed by Golgi vesicle fusing Then these structures join together and form the walls of endosperm cells.No microtubule is obserued in the joining process.Wall ingrowths appear on the outer periclinal walls and anticlinal walls ofendosperm cells.