鹤顶兰胚囊发育过程中Ca~（2＋）分布的超微细胞化学定位（英文）

用焦锑酸盐沉淀法对鹤顶兰（Phaius tankervilliae）胚囊发育过程中的Ca2＋状态进行超微细胞化学定位。观察结果发现：功能大孢子时期,珠孔端的胚囊壁上开始出现小颗粒的Ca2＋沉淀,但功能大孢子细胞内未见明显的Ca2＋标记;四核胚囊时期胚囊壁上的Ca2＋沉淀明显增多,液泡膜上有Ca2＋沉淀出现,珠孔处的Ca2＋沉淀颗粒较大;成熟胚囊时期,胚囊壁上的Ca2＋沉淀进一步增多,且胚囊内Ca2＋分布明显增多,且极性明显,珠孔端助细胞、卵细胞比合点端反足细胞有更多的Ca2＋沉淀。鹤顶兰成熟胚囊内Ca2＋积累的来源有：（1）在胚囊成熟前主要由珠被细胞、珠细胞通过胞间连丝向胚囊运输;（2）以沉淀有大量Ca2＋的小泡形式跨过胚囊壁进入胚囊。

Ultracytochemical Localization of Calcium during Embryo Sac Development in Phaius tankervilliae(Orchidaceae)

Ultracytochemical localization of calcium in embryo sac of Phaius tankervilliae(Aiton) Bl. was carried out using potassium pyroantimonate precipitation method. Results of Ca2+ distribution during embryo sac development are as following: (1) Megasporocyte stage: There is no Ca2+ precipitation in the megasporocyte, nucellar cell and micropyle; (2) Functional megaspore stage: Small particles of Ca2+ precipitates appear on the embryo sac wall at the micropylar end, but no apparent Ca2+ can be found in the functional megaspore; (3) 4-nucleate stage: There are significant increase of Ca2+ precipitation on the embryo sac wall and large grains of the precipitates in the micropyle, while a little starts to appear on the membrane of vacuole; (4) 8-nucleate embryo sac stage: Ca2+ precipitation continuously increases on the embryo sac wall. Distribution of Ca2+ in embryo sac shows strong polarity. More Ca2+ precipitations are observed in the synergids and the egg cell than the antipodal cells. Accumulation of Ca2+ precipitation is achieved by (1) transferring Ca2+ to embryo sac through the plasmodesmata between the nucellar cells, which mainly occurred at the chalaza end before the embryo matured; (2) forming large amounts of small bubbles of Ca2+ precipitation, which can cross embryo sac wall to enter embryo sac.