Dinis A M, Santo Dias J D, Mesquita J F
Department of Botany, University of Coimbra, Portugal.
J Submicrosc Cytol Pathol. 2000 Oct;32(4):591-601.
The structural organization of the Michelia figo mature pollen was investigated. The pollen wall consisted of an outer exine and an inner intine, the former being coated by a thin polysaccharide pellicle. The intine comprised three structurally distinct layers that were equally thick throughout the pollen surface. The generative cell (GC) was closely associated with the vegetative cell (VC) nucleus and its periplasm was found to maintain communication with the sporoderm through a complex plasmalemmic cord. In the freeze-fixed pollen a fluffy coat was detected on the cytoplasmic face of the VC plasmalemma bordering the GC. The plastids were present in only the VC and usually contained abundant small starch grains. In a few pollen grains, however, little or no starch existed and in this case one or more electron dense inclusions appeared in the plastids. Microbodies were found in both the VC and GC. In the VC they presumably have a glyoxysomal function as indicated by the numerous lipid droplets in the cytoplasm and the spatial relationship of microbodies with lipid droplets and/or mitochondria. In the GC the function of the microbodies is unclear once this cell had no abundant lipid reserves and the microbodies did not show any preferential relationship with other organelles. The most conspicuous feature of the VC cytoplasm was the high amount of storage vacuoles which displayed a striking different appearance after one and the other of the fixation techniques used. In contrast to the chemically fixed pollen they were quite polymorphic in the freeze-fixed pollen, and appeared uniformly filled with fibrillar material. Enzymatic digestion with protease has revealed most of this material to be proteinaceous in nature. The existence of phytin reserves is, however, also probable. These protein storage vacuoles closely resemble those in storage tissues of seeds and fruits.
对含笑成熟花粉的结构组织进行了研究。花粉壁由外层的外壁和内层的内壁组成，外壁被一层薄的多糖薄膜覆盖。内壁由三层结构不同的层组成，在整个花粉表面厚度均匀。生殖细胞（GC）与营养细胞（VC）的细胞核紧密相连，发现其周质通过复杂的质膜索与孢子体保持通讯。在冷冻固定的花粉中，在与生殖细胞相邻的营养细胞质膜的胞质面上检测到一层蓬松的涂层。质体仅存在于营养细胞中，通常含有丰富的小淀粉粒。然而，在少数花粉粒中，淀粉很少或不存在，在这种情况下，质体中会出现一个或多个电子致密内含物。在营养细胞和生殖细胞中都发现了微体。在营养细胞中，它们可能具有乙醛酸循环体的功能，这可以从细胞质中大量的脂滴以及微体与脂滴和/或线粒体的空间关系中看出。在生殖细胞中，微体的功能尚不清楚，因为这个细胞没有丰富的脂质储备，并且微体与其他细胞器没有任何优先关系。营养细胞胞质最显著的特征是大量的贮藏液泡，在使用的两种固定技术处理后呈现出明显不同的外观。与化学固定的花粉相比，它们在冷冻固定的花粉中非常多样，并且看起来均匀地充满了纤维状物质。用蛋白酶进行酶消化表明，这些物质大部分本质上是蛋白质。然而，也可能存在肌醇六磷酸储备。这些蛋白质贮藏液泡与种子和果实贮藏组织中的液泡非常相似。
