南瓜叶片中的胞间连丝类型与分布

The Types and Distribution of Plasmodesmata in Pumpkin Leaf Blades

胞间连丝是植物调节生长、发育所不可缺少的细胞器,为了解南瓜叶片胞间连丝的类型和分布,试验对叶片不同细胞界面上的胞间连丝进行超微观察。结果表明,叶片内有简单胞间连丝和分支胞间连丝两种类型,简单胞间连丝出现在叶肉细胞-叶肉细胞界面及叶肉细胞-伴胞界面,分支胞间连丝出现在表皮细胞-叶肉细胞界面、叶肉细胞-伴胞界面以及伴胞-筛管界面。在叶肉细胞-伴胞界面上既有简单胞间连丝又有分支胞间连丝,但以分支胞间连丝为主。叶肉细胞-伴胞界面上胞间连丝不是随机分布,而是聚集在某些直径1.5~3μm的区域内,这些区域内胞间连丝密度高达122个/μm~2,为光合产物的韧皮部装载提供了共质体途径。胞间连丝的不同类型及其分布特点为超微水平认识南瓜叶片提供了新视角。

Plasmodesma is essential organelles for regulating plant growth and development.In order to characterize plasmodesmata in pumpkin leaf blades,these organelles at the interfaces between different cell types were examined by means of transmission electron microscopy.Two types of plasmodesmata were observed,simple plasmodesmata and branched plasmodesmata.Simple plasmodesmata were found at the interfaces between mesophyll cells and between mesophyll cells and companion cells.Branched plasmodesmata were demonstrated at the interfaces between epidermal cells and mesophyll cells,between mesophyll cells and companion cells,and between companion cells and sieve elements.Branched plasmodesmata predominated at the interface between mesophyll cells and companion cells,although there were two types therein.Plasmodesmata were not randomly distributed at the interface,but assembled in areas 1.5-3μm in diameter.The density of plasmodesmata in the aggregation area was up to 122 perμm2.Such a large density provided a symplastic pathway for phloem loading of photosynthetic products.The types and distribution pattern of plasmodesmata provided a new perspective for understanding leaf blade at ultramicroscopic level.