马尾松主要器官树脂道的发生和发育

Initiation and Development of Resin Ducts in Major Organs of Pinus massoniana

利用半薄切片、超薄切片方法研究马尾松主要器官中树脂道的结构、分布、发生和发育过程,以及树脂道发育过程中的超微结构变化。结果表明：马尾松树脂道是由一层上皮细胞围绕着伸长的胞间道而构成的,上皮细胞外又有1～2层鞘细胞。树脂道几乎分布于所有器官中,仅子叶中未观察到树脂道。树脂道以裂生方式形成,其发育过程可分为3个阶段：原始细胞阶段、形成阶段和成熟阶段。在原始细胞阶段,原始细胞中含较多的质体,质体中缺乏完整的膜结构,在质体外膜及内质网上可见到少量嗜锇滴。在形成阶段,上皮细胞内质体数量增多,质体外常见到内质网鞘包裹,各种细胞器的数量增加。在成熟阶段,上皮细胞内各细胞器的数量逐渐减少,但质体仍很多,嗜锇滴多。

The structure, distribution and the patterns of resin ducts in processes of its initiation and development were studied with the methods of thin section and ultra-thin section. This paper emphasized the uhrastructual changes during canal development in Pinus massoniana. Our observations revealed that the resin ducts were relatively large intercellular spaces surrounded by a ring of the alive epithelial cells, and the epithelial cells were usually surrounded with one or two layered sheath cells, which were normal parenchyma cells in some primary resin ducts and became dead cells with thick walls in other primary and secondary resin ducts. The resin ducts were found to occur in almost all organs, except in cotyledon. The resin ducts were formed by Schizolysigeny according to characteristics of cell morphologic changes at the different stages of canal development and three developmental stages could be divided, namely initial stage, formative stage and mature stage, respectively. At the initial stage, the initials had dense cytoplasm and the abundant plastids in large size and elliptical shape, which contain one or two starch grains, without internal structure visible apart from a few short membranous profiles. A small number of osmiophilic droplets were present in the plastids. At the formative stage, the plastids, mitochondria and Golgi bodies in the cytoplasm increased in number. The plastids were commonly surrounded by an endoplasmic reticulum （ER） sheath. The larger osmiophilic droplets in cytoplasm and the smaller osmiophilic droplets on the plastids envelope, mitochondrion envelope and in Golgi vesicles obviously increased in number while canal developing. At the mature stage, the cytoplasm of epithelial cells became thin with a small nucleus. The number of mitochondria and Golgi body decreased, but numerous plastids still existed. Osmiophilic droplets were abundant in epithelial cells as previous status. The structures of plastids in epithelial cells gradually became well-developed so that the synthesis of resin remarkably enhanced during resin ducts formation and plastids would be main site for resin synthesis.