青藏高原草地植物叶解剖特征

运用常规石蜡制片技术对我国青藏高原66种草地植物优势种的叶解剖特征进行研究,并分析了叶解剖特征与海拔、生长季降水及生长季均温之间的关系.结果表明:青藏高原草地植物叶片具有很多适应高寒环境的结构特征,如表皮层厚且表皮细胞大小差异显著,表皮毛等表皮附属物发达,异细胞丰富,通气组织普遍发达等；叶片各组成部分厚度的变异程度不同,其中海绵组织厚度变异最大,其次为上角质层、下表皮层、下角质层、上表皮层、栅栏组织,叶片厚度的变异最小；青藏高原草地植物叶片各组成部分的厚度存在协同进化,上下角质层厚度呈强烈正相关,海绵组织厚度与叶片厚度相关性最强；青藏高原草地植物叶片各组成部分的厚度与海拔、生长季降水、生长季均温3个重要环境变量呈较弱的相关性,总体表现为随海拔升高叶片各组成部分的厚度减小,而随生长季降水和生长季均温的增加叶片厚度增加.

Leaf anatomical characteristics of the plants of grasslands in the Tibetan Plateau

As exposed to the air, plant leaves are sensitive to the changes in environments. In this study, we investigated the leaf anatomical characteristics and their correlations with environmental variables for 66 dominant species of grasslands in the Tibetan Plateau. The results showed that: (1) Plants of grasslands on the Tibetan Plateau showed typical characteristics to adapt to the alpine environments, such as thicker epidermal and mesophyll layers than plants in other areas. In detail, epidermal cells of some plants can be differentiated into special structures such as blister cells and epidermal hair; mesophyll cells had thick cell walls, dense cytoplasm with rich reserves, containing large volume and amount of chloroplasts. Besides, the thick palisade tissue was composed of multi-layers of tightly arranged small-volume cells. The spongy tissue was composed of relative small cells, with large intercellular space, however, its thickness varied greatly among species. Most of the plants had well-developed aerenchymas and sclerenchymas in the mesophyll cells, with the advanced sclerenchymas around the veins and vascular bundles often extending to the leaf surface. Many vascular bundle sheaths and idioblasts (reserve cells) were observed within the mesophyll cells. For most plants, these idioblasts existed in (or around) the vascular tissues; furthermore, the idioblasts existed in one or two cell layers of palisade tissue near upper epidermis for over half of the plants. (2) Thickness of leaf anatomical structures varied in different degrees; in particular, thickness of spongy tissue exhibited the greatest variation (0.34), followed by that of upper epidermal cuticle (0.33), lower epidermis (0.28), lower epidermal cuticle (0.26), upper epidermis (0.26), palisade tissue (0.25) and the leaf as whole (0.17). (3) Thicknesses of leaf anatomical structures were negatively correlated with altitude, thicknesses of all anatomical structures except the upper cuticle were positively correlated with precipitation for growing season; thicknesses of all leaf anatomical structures except the lower cuticle were positively correlated with mean temperature for growing season. These results suggested that different components of the leaf were relatively thin at high altitudes, and the leaf was relatively thick in the areas with high precipitation and mean temperature for growing season.