白皮松成熟胚细胞的微体分布与超微结构特点

THE ULTRASTRUCTURAL FEATURE AND DISTRIBUTION OF MICROBODIES IN MATURE EMBRYO CELLS OF PINUS BUNGEANA

白皮松成熟胚细胞中的微体,主要分布于根冠组织和下胚轴的皮层细胞中,在这些细胞中脂体是最基本而丰富的成分,其中微体则被许多脂体紧紧包围;在子叶中,虽然脂体更为丰富,并彼此强烈挤压,但微体却很少。成熟种子中的微体,属乙醛酸循环体类型,其超微结构特点是很明显的,它除了单层膜的束缚外,基质中具有电子致密的无定形内含物或规则排列的晶体点阵。

The material of pine seeds used in this investigation was collected in 1982 from Peking. The microbodies of mature embryo cells are very well developed and their diameter averages about 2-3 μm, even up to 4.3 μm. The appearance is usually ovoid or elliptic. The mierobodies are essentially glyoxysomes. The microbody matrix is composed of two types of substances, one type is of a finely granular material in a densely arrangement (Plate Ⅲ Fig. 6) ; the other is of coarsely granular or flocculant in appearance and the elements of the matrix are loosely distributed. These matrices usually contain an amorphous inclusion or crystalline arrays in regular arrangement. The inclusion sometimes occupies a small portion of the microbody matrix (Plate Ⅲ, Pigs. 5, 6) and sometimes the inclusion occupies nearly the entire glyoxysome (Plate Ⅱ, Fig. 3). It is interesting that the "pockets" frequently appear in the microbodies of mature embryo cells, and those are actually as a result of invagination in microbodies (Plate Ⅱ, Fig. 4). In addition, an electron-transparent "oil body-like space" occurs occasionally in microbody (Plate I, Fig. 1). The periphery of "space" is a constitutive part of matrix or continuing with the matrix. This "space" may be due to the degradation in a part of the matrix. While the periphery of the pocket is membranaceous and an electron-opaque cytoplasmic groundplasm was found within the pocket. The microbodies of mature embryo cells in Pinus are mainly distributed in perico-lumn cells of the root cap and cortical cells of the hypocotyl. Besides the dominant organelles of lipid bodies in the cells of above mentioned tissues, there are also micro-bodies, amyloplasts, mitochondria, plastids, endoplasm reticulum and Golgi apparatus, of which the microbodies are the most aboundant organelles. In contrast, the microbodies and other organelle are rare in the parenchyma of the cotyledons in Pinus. Their common and outstanding characteristics in various tissues of mature embryo is that the entire cytoplasm of the cells is almost full of the lipid bodies, and each organelle is directly surrounded by a number of lipid bodies (Plate Ⅰ—Ⅲ, Figs. 1-6). Because of the other organelles are rare in parenchyma of the cotyledons, the lipid bodies are so appressed with each other that the inlaid periphery of lipid bodies frequently occurs in some degree. To sum up, based upon the state of distribution of microbodies in mature embryo tissues, cotyledons of Pinus could be considered as the main storage organ of nutrient substances, while the root cap and hypoeotyl are the important sites of glyoxysome metabolism. The function of glyoxysomes is to convert lipid into the carbohydrates and to transfer the latter to embryos for growth.