青藏高原不同海拔3种菊科植物叶片结构变化及其生态适应性

Structure and ecological adaptability of the leaves of three asteraceae species at different altitudes on the Qinghai-Tibet Plateau

采用常规石蜡制片技术和显微观察方法,对分布于青藏高原祁连山东部山地冷龙岭3600—4400 m不同海拔高度的蒲公英(Taraxacum mongolicum Hand-Mazz)、火绒草(Leontopodium leontopodioides(Willd.)Beauv)和美丽风毛菊(Saussurea superba Anthony)的叶片形态解剖结构进行了研究,并探讨了其对海拔高度的响应及生态适应性。结果表明:随海拔高度的升高,3种植物气孔器外拱盖内缘、角质层纹饰、气孔与表皮细胞的位置关系以及上、下表皮气孔器内缘呈现不同的变化趋势;火绒草上、下表皮气孔密度随海拔升高而增加,而蒲公英和美丽风毛菊的气孔密度则降低;3种植物上、下表皮气孔指数随海拔高度的增加均未出现规律性变化;3种植物叶片厚度、上下表皮厚度、上下角质层厚度、栅栏细胞系数均随海拔升高而增加;解剖学指标之间大多呈明显的协同进化;叶片结构,尤其是气孔密度对海拔高度变化表现出较大的可塑性。研究表明3种植物采取不同的响应机制来适应海拔高度的变化,植物对高原环境变化的适应具有多样性。

To investigate the impacts of climate change on plants,the paraffin section method and microscopic techniques were used to study the morphological and anatomical structures of Taraxacum mongolicum Hand-Mazz,Leontopodium leontopodioides（ Willd.） Beauv,and Saussurea superba Anthony leaves. These species are distributed at different altitudes（3600 m to 4400 m） in the eastern part of the Qilian Mountains on the Qinghai-Tibet Plateau. Leaves,as the organs with the largest surface area exposed to the sun and air,are the main photosynthetic organs of most plants,and very sensitive to environmental changes（ e. g. light,temperature,moisture etc.）. Thus,leaves can exhibit great phenotypic plasticity in response to environmental heterogeneity,as both the external morphology and internal anatomy of a leaf can vary extensively with changes in environmental conditions. The Qinghai-Tibet Plateau is one of the areas most vulnerable to the effects of global climate change,because of its high altitude. In this study,we observed the morphological features of leaves,calculated their anatomical indexes and stomatal parameters, and analyzed the correlation between the anatomical characteristics of the above Asteraceae plants. We also investigated the response and ecological adaptability of these plants to differences in altitude. The results showed that the three plants undergo different changes in the inner margin of the outerstomatal ledge,cuticular ornamentation,relative positions of stomata and epidermal cells,as well as the inter-margin of the upper and lower epidermal stomatal apparatus with increased altitude. The average stomatal density of on upper and lower epidermis of Leontopodium leontopodioides increased with altitude; however,the opposite effect was observed in Taraxacum mongolicumand Saussurea superba. The three plants underwent an irregular change in the stomatal indices of the upper and lower epidermis with the increase in altitude. The area of the stomatal apparatus of the upper and lower epidermis of Taraxacum mongolicum and Leontopodium leontopodioides gradually increased with altitude（ there was no significant differences at the 0. 05 level in the stomatal apparatus area of upper epidermis of Leontopodium leontopodioides between 3800 m and 4400 m above sea level）,while the area of the stomatal apparatus of Saussurea superba first decreased,then increased when the altitude increased from 3600 m to 4000 m. The thicknesses of the leaves,upper and lower epidermis,upper and lower cuticle,and coefficient of the palisade cell increased with altitude. The results indicate the occurrence of a significant co-evolution between most leaf anatomic indexes（ for example,upper and lower cuticle thickness and epidermis thickness,palisade tissue thickness and spongy tissue thickness,coefficient of palisade and coefficient of palisade cell,and mesophyll cell area and volume）. The anatomical structures of the leaves,and the stomatal density in particular exhibited highly plastic responses to changes in altitude. These results suggest that the anatomical structures responded similarly to altitude change among the three species,and that the co-evolution and plasticity of leaf anatomy were driven by environmental variation. The different plants possess different response mechanisms that allow them to adapt to changes in altitude,which confer adaptability to environmental changes on the Qinghai-Tibet Plateau.