银杏叶表皮结构

THE EPIDERMAL STRUCTURE OF GINKGO LEAF

银杏(Ginkgo biloba L.)的叶片形态与表皮结构有多种变异,上下表皮层细胞的形态结构差异也较大。上表皮细胞排列比较整齐、表面平滑;而下表皮细胞排列很不规则,细胞壁突起的方向不一,且壁上具有绉纹。叶子上表皮气孔数目稀少,且多局限在叶片基部,所以常被忽视,但是也有的只有下表皮具有气孔。气孔的保卫细胞下陷很深,而围绕的4—7个副卫细胞顶上突起,覆盖了气孔。在下表皮上,常可看到二个气孔甚至于三个气孔着生在一起,这在其它种子植物中非常少见。

Ginkgo biloba L.has often been called a living fossil.Significant variations are often seen in its leaf form and structure of the epidermal layer and the morphological differences between the upper and lower layer.In the upper epidermal layer,the cells are rather orderly arranged in the appearance of a smooth surface.However,the cells of the lower layer are very irregularly arranged.The Cell wall projects in various directions and is wrinkled.The sto- mata in the upper layer are rare and are restricted to the base of the leaf blade,for which they are often neglected.However,in some incidences,they are present only in the lower layer. The guard cells are deeply caved in by the surrounding 4—7 subsidiary cells,the upper part of which projects and covers the stoma.In the lower layer,two stomata,or occasionally three, that set close to each other might be observed.These phenomena are scarcely seen in other seed plants.