臭椿不同发育阶段叶片表面结构特征

利用光学显微镜和扫描电子显微镜技术,对臭椿(Ailanthus altissima(Mill.)Swingle)叶片从叶芽到成熟叶4个发育阶段(叶芽、幼叶、近成熟叶和成熟叶)的4种叶表面结构(表皮毛、气孔器、角质层、腺体)进行了详细地观察和比较。结果显示:叶片上、下表面具单细胞非腺毛和头状腺毛两种表皮毛,其密度在叶芽阶段最大,之后随着叶片的生长和展开表皮毛密度逐渐降低;气孔器主要分布于下表面,叶片近成熟时气孔器密度最大;角质层具有条纹状结构,其隆起程度在近成熟叶阶段达到最大;叶片基部两侧具锯齿状突起,每个突起上有一个腺体,腺体发育成熟后可分泌透明黏液。说明叶片表面各结构特征是臭椿对环境长期适应的结果。

Leaf Epidermal Features of Ailanthus altissima (Mill.) Swingle in Different Development Stages

The leaf epidermal features of Ailanthus altissima (Mill.) Swingle,including epidermal hairs, stomatal apparatus, cuticles and glands, were examined at different development stages (leaf bud, young, near-mature and mature leaf) under light microscopy (LM) and scanning electron microscopy (SEM). We observed two kinds of epidermal hairs on both sides of the leaf, that is, single-celled non-glandular hairs and capitate glandular hairs. Hair densities were greatest in the leaf bud, then decreased gradually with leaf development. The stomatal apparatus was mostly found on the lower leaf epidermis, and stomatal density was greatest in the near-mature leaf. The leaf epidermis was covered with striated cuticles, which showed maximum swelling degree in the near-mature leaf. Leaves had serrated protuberances on the leaf basal part. Each protuberance had one gland, which produced transparent mucus when mature. The epidermal features of A. altissima leaves reflect their adaptation to environments during long-term evolution.