白木香叶解剖结构的研究

Studies on Anatomical Structure of the Leaves of Aquilaria sinensis

用石蜡切片法制片,光学显微镜观察,研究白木香叶的解剖结构。结果表明,白木香叶为典型的异面叶,但同时还表现出许多旱生形态。表皮由一层排列紧密形状不规则的表皮细胞组成,细胞外壁角质膜较厚。上表皮角质膜一般较下表皮角质膜厚1μm,下表皮上零星分布着单细胞表皮毛。气孔仅分布在下表皮上,微下陷,气孔类型为无规则型。叶肉组织发达,其间分布着较多的长方晶体,其细胞长轴与表皮垂直。栅栏组织由1-2层排列整齐的圆柱形细胞组成。栅栏组织的外层细胞转化为异细胞,海绵组织内具有一层由异细胞组成的下皮层;横切面上栅栏组织厚度与海绵组织厚度之比为13∶。主脉发达,有异细胞组成的维管束鞘,具双生韧皮部。叶内具有发达的木质部外纤维。这些特征与旱生环境相适应。

Leaf structure of Aquilaria sinensis （Lour.） Gilg （Thymelaeaceae） observed under light microscope shows that the leaves are of typically bifacial exhibiting xeromorphic characters. Epidermis consists of a row of irregular epidermal cells with thick horny layers and are closely arranged. The horny layers in upper epidermis are 1μm thicker than that in lower epidermis. Sunken stomata exist only in lower epidermis which is sparsely covered by unicellular hairs. The stomata are of anomocytic type. Mesophyll is well developed, in which many rectangular lithocyst arranged perpendicularly to the epidermis. Palisade parenchyma is composed of 1-2 layers of cylindrical cells. The cells in outer layer of palisade parenchyma are transformed into idioblasts. In spongy parenchyma there is a layer of hypodermis which is composed of idioblasts. The ratio of the thickness of palisade parenchyma to spongy is 1： 3. The micrib belonging to bicollateral bundle is well developed. The bundle sheath is composed of idioblasts. The leaves are rich in extraxylary fibres. The structural characteristics show that it is a xerophytic species adapted to arid environment.