侧柏小孢子囊壁绒毡层和中层细胞的发育

Studies on the development of tapetum and middle layer of microsporangium in Platycladus orientalis

侧柏 [Platycladusorientalis (L.) Franco]小孢子囊壁包括 3层细胞 :表皮、中层和绒毡层。中层细胞为 1层扁平的细胞。绒毡层细胞属于分泌型。成熟的绒毡层细胞除了有单核和双核细胞外 ,还有三核和四核等多核细胞。细胞核有圆形和长椭圆形 2种形态。绒毡层细胞的染色质伴随着小孢子母细胞减数分裂有一个浓缩和伸展的时期 ,这个时期影响营养物质向小孢子囊内部转运。绒毡层细胞发育的初期就为造孢细胞提供营养 ,后期解体时 ,分泌的乌氏体不是散乱地而是有组织地向花粉粒的表面转移。

The microsporangium wall cell of Platycladus orientalis (L.) Franco consists of three layers:the epidermis,the middle layer and the tapetum.The form of middle layer cell is flat.The tapetum is secretery type.There are tri and tetra caryotic cells in mature tapetum as well as mono and di caryotic cells.The form of tapetal cell nucleus is round or long elliptical.The reason of the formation of polycaryotic cell is that the nuclear division of dicaryotic tapetal cell.The chromatin of tapetal cell has a period of becoming condensed and then spreading accompanying the meiosis of the microspore mother cells,which will affect the entering of nutrient into the inner part of microsporangium.The tapetal cell has under taken the task of providing nutrition for the sporogenous cells at earlier development.Ubisch body secreted from tapetal cell later transport to the surface of pollen grain not in scattered but in organized form.The middle layer and the tapetum cells are totally absorbed as nutrient at last.