棉花小孢子发育过程中巨大的叠堆粗面内质网及其活动

THE GIANT STACKED ROUGH ENDOPLASMIC RETICULUM AND ITS ACTIVITY DURING COTTON MICROSPORE DEVELOPMENT

棉花(Gossypium hirsutum L.)小孢子发育过程中,从四分孢子的后期至大液泡开始出现,外层细胞质中普遍存在叠堆的粗面内质网(S-RER),并且具相当多的数量。这种RER的叠堆是巨大的,可在光镜下见到,直径在2—4.5 μm。S-RER的结构形式是多样的,可归纳为两种主要的类型:一种是小的简单的叠堆,只含少数几个平行排列的潴泡。另一种是大的复杂的叠堆,集聚的潴泡可达50多个。在两种极端大小的S-RER之间存在各种不同大小的叠堆。此外,还观察到一些S-RER具特殊的形态,其中的潴泡的边缘变为囊泡状。这种构型可能代表了S-RER将通过潴泡的的膨大囊泡化而失去原来的结构形态。此外,S-RER还能活跃地形成小泡的活动,小泡在膜上具核糖体颗粒。小泡的动向:一是向细胞表面的质膜转移,并与质膜融合;二是小泡相互之间融合成较大的囊泡,形成原液泡体,并逐渐转化为小液泡。本研究结果得出如下结论:1、在棉花小孢子发育过程中存在的S-RER虽然在结构上与某些植物中报道过的成熟花粉粒中的相似,但棉花小孢子中S-RER不象在成熟花粉粒那样是活动能力低的,而是处于高度活动的功能状态,表明S-RER的结构形式不一定是不活动的特点。2、在棉花小孢子发育中,在体积迅速增大时,伴随发生液泡的增多和扩大,必然涉及细胞表面质膜和内部液泡膜的构建,表明S-RER的一个重要功能是提供质膜和液泡膜的构建物质。

The giant stacked rough endoplasmic reticulum (S-RER )is discovered in the study of cotton microsporogenesis. These giant S-RER are randomly dispersed in the outerpart of the microspore cytoplasm and are easily visualized,because they have sufficient number and are large enough for examination under light microscope. The diameters of those stacks attain to a range of 2.0 — 4. 5μm. Specific characteristics of S-RER vary with the developmental stage and metabolic state, but they may be included into two main types:one is small and simple,the other is large and complex. The giant stacks may be composed of more than 50 parallel cisternae. Of course, between the main types there are many transitional forms. In addition,a few special configurations of S-RER was observed which the cisternae always become vesicularized at the peripheral portion of the stacks occurring near the plasma membrane (PM). In this case,the S-RER itself may be further lost its own structural property,instead of substituted a lot of small vesicles at its original site. It may also be called vesicular RER . Those vesicles derived from RER cisternae bear ribosomes on the outer surface. On the other hand,vesicles as a major vesicle may be directly formed at the ends of RER cisternae,which,in fact,serve as transition elements. The dynamic activities of those vesicles during the spore metabolic processes are conducted via two pathways operative; (1)the vesicles detach from the RER end and migrate towarss PM,then the vesicle membrane fuses with PM and the contents of the vesicles are discharged, (2) vesicles fuse together among themselves to form provacuolar bodies in the outer part of the spore cytoplasm. Several provacuolar bodies may further converge more and more to form small vacuoles. From the data studied the following conclusions may be drawn:(1)although the S-RER presented during cotton microsporogenesis is much the same as that in mature pollen grains of some plants, yet in this study S-RER always shows functional activities. So that S-RER is not limitted to represent an inactive RER configuration. (2)During the development of cotton microspore,the enlargement of the cell size is bound to follow a rapid increase and great extension of the vacuoles. It indicates that a rapid synthesis of en-domembrane materials must be involved in the growth of microspore. The supply of membrane materials is one of the important functions of S-RER.