胡杨不同发育阶段叶片光合作用及其光响应特征

Leaf photosynthesis and light response characteristics of Populus euphratica in different developmental stages

胡杨(Populus euphratica)为第三纪孑遗植物,在个体的不同发育阶段形成了独特的异形叶,具有较强的抗旱性和耐盐性,是额济纳绿洲生态系统的主要建群种,具有重要的研究价值。以内蒙古额济纳旗胡杨林自然保护区胡杨为研究对象,通过实地调查观测,分析了胡杨幼苗期、幼树期和成熟期叶片的形态变化规律及其性状特征,利用Li-6400XT便携式光合作用系统测定了胡杨幼苗期、幼树期和成熟期不同形态叶片的光合作用光响应过程,并采用直角双曲线修正模型对其进行了拟合分析。结果表明:(1)在胡杨生长发育过程中,其叶片形态性状表现出明显的变化规律。随着胡杨树龄的增长,其叶片的长/宽比值、比叶面积和叶片厚度逐渐减小,而叶干物质含量、叶面积和叶干重数据增大。(2)胡杨成熟期阔卵圆形叶具有较高光合活性,通过提高Pnmax以增强光能利用率,使其在干旱荒漠区高温、强光环境下仍能保持较高的光能转化效率与光合速率;幼树期条形叶具有较宽的光能利用区间,能够在弱光环境下保持较高的光合速率;幼苗期条形叶具有较低的α与相对较高的LCP、LSP及Pnmax,主要归因于其较高的比叶面积,高效光捕获面积使其具有较高的光合速率;上述结果是胡杨在不同光环境下形成的适应性反应和生理生态机制。(3)直角双曲线修正模型适于胡杨不同形态叶片光合生理参数的定量研究。

Populus euphratica is the tertiary relic plant with various forms of leaves at different stages of individual development.It is very important to study on the drought resistance and salt tolerance of P.euphratica,which is the major dominant species of oasis ecosystem in Ejina area,Inner Mongolia.It was analyzed for the leaf morphological characteristics,photosynthesis and light response process of P.euphratica at different developmental stages.The results showed that the ratio of length to width,specific leaf area and leaf thickness of P.euphratica decreased from seedling stage,young tree stage to mature tree stage,while the leaf dry matter content,leaf area and leaf dry weight increased.The higher photosynthetic efficiency and photosynthetic activity of broad oval leaves of P.euphratica at mature stage were maintained to increase photosynthetic rate under desert environment of high temperature and strong light.The higher photosynthetic rate of strip leaves at young tree stage was related to wider range of light energy utilization under weak light environment.The higher photosynthetic rate of strip leaves at young seedling stage was maintained due to higher specific leaf area and light capture,while light compensation point(LCP)and light saturation point(LSP)were also higher.The above results provided the base of adaptive responses and eco-physiological mechanisms of P.euphratica under different light environments.It was proved that the modified model of rectangular hyperbola was suitable for quantitative study of photosynthetic physiological parameters of different leaves of P. euphratica.