侧柏小孢子的发生和雄配子体的形成

STUDIES ON THE MICROSPOROGENESIS AND THE FORMATION OF THE MALE GAMETOPHYTE IN PLATYCLADUS ORIENTALIS

侧柏[Platycladusorientalis（L．）Franco]初生造孢细胞在8月下旬（1992年）形成，11月上旬形成小孢子母细胞，1993年2月中旬形成四分体，2月下旬小孢子从四分体内释放出来，3月中旬形成成熟花粉粒并开始传粉，4月上旬花粉粒在珠心上萌发，5月上旬生殖细胞分裂，6月上旬精原细胞分裂。小孢子母细胞在休眠以前开始减数分裂，解除休眠以后形成成熟的花粒粒。减数分裂从11月上旬开始至次年2月17日结束。小孢子母细胞减数分裂存在扩散双线期。小孢子母细胞以双线期渡过休眠。精原细胞接近颈卵器时开始分裂，形成两个大小相同的精细胞。精细胞独立存在的时间很短。精细胞的细胞质分为三个区域。小孢子母细胞在发育过程中，发现有部分小孢子母细胞退化，在小孢子囊内形成一大的空腔的现象。

This paper mainly deals with the microsporogenesis and the formation of the malegametophyte of Platycladus orientalis (L.) Franco.Primary sporogenous celle wasformed in the late August (1992);microspore mother cells (MMC) were formed in theearly Novemberl next year (1993),in the middle of February tetrad was formed;microspores were released from tetrad in the late February;mature pollen grain was formedand began shedding in the middle of March;pollen grain germinated in the early April;generative cell divided in the early May;spermatogenous cell divided in the early June.Meiosis of MMC of P.orientalis begins before dormancy,while mature pollen grain isformed after dormancy.Especialy there is a diffuse diplotene stage during MMC's meiosis which begins from early November (1992) to later middle February next year.MMCgo through dormancy at the stage of diplolene.After pachytene,MMC enter into a diffuse diplotene and go through dormancy at the same time,rather than pass directly tothe next typical diplotene.Approching the archegonium,spermatogenous cell begins celldivision and gives rise to two sperm cells of the same size.The time of independent existence of the sperm cell,whose cytoplasm is evidently divided into three region by haemotoxylin staining,is very short.During the development of MMC,we find that there is aphenomenon which takes place in the microsporangium:part of MMC begins to degenerate,resulting in the formation of a large cavity by the time Feb.18.