2种水分生境下红砂叶片功能性状的响应及适应机制

Responses of Leaf Functional Traits of Reaumuria soongorica in Two Different Desert Habitats

干旱是中国西北荒漠生态系统的主要特点之一,干旱对植物的生长、发育、繁殖及分布等产生重要的影响。红砂是广泛分布在我国温带荒漠草原生态系统中的优势种和主要建群种之一,对多种环境胁迫尤其是干旱胁迫具有极强的耐受性。因此,研究红砂对不同水分生境的响应及适应机理有着重要的科学意义。对不同水分条件自然生境中(小红山地区和长流水地区)的红砂叶片形态、表皮微形态及超微结构进行分析,揭示红砂适应干旱胁迫的叶片形态结构特征。结果表明,随着生境中土壤含水量的降低,红砂叶片厚度增大,叶面积及气孔开度减小,角质层增厚,从而降低植物蒸散过程中体内水分的散失。表皮细胞面积减小,表皮细胞密度增大,细胞壁增厚,增加了表皮细胞弹性,有助于降低干旱胁迫下植物失水造成的机械损伤。与此同时,栅栏组织增厚,且细胞排列更加致密,海绵组织的厚度减小,在一定程度上促进叶片的光合作用进行。因此,红砂叶片的形态结构特点使其对干旱具有极强的耐受性。研究揭示了荒漠植物红砂的叶片形态结构对不同水分条件的响应,为理解荒漠植物对水分限制的响应机制提供数据支持。

Reaumuria soongorica,a shrub species widely distributed in semi-arid and arid desert areas of northwestern China,can survive in severe environmental stresses.In order to explore responses of leaf functional traits to different soil water contents,leaf areas,epidermal micromorphology and mesophyll structure were investigated.Samples were collected from two sites with different soil water contents.The results showed that with the decrease of soil water content,the thickness of leaf and cuticle increased,and the leaf area and stomata opening decreased.All those variations were considered to be strategies of R.soongorica to reduce water loss to a minimum in transpiration process.Increases of epidermal cell size,density and cell wall thickness could improve the plasticity of epidermal cells,consequently mitigate the mechanical damage in water loss process.Meanwhile,the thickness and density of palisade tissue increased,resulting in the improvement of photosynthesis rate.Our results indicate that the leaf functional traits of R.soongorica is closely correlated with soil contents,and play important roles in response to desert drought environment.