Individual Differences With Twig-leaf Traits And Photosynthesis Of Tamarix Ramosissma In The Heihe National Nature Reserve Of Zhangye

Light is one of the most important environmental factor that affect the survival, growth and regeneration of plants. The response of plants to different light intensity is mainly achieved through the regulation of external morphology and internal physiological characteristics. The growth pattern of branches and leaves determines the material exchange capacity between plants and the environment, and the different speed growth pattern of branches and leaves is of great significance for understanding plant phenotypic plasticity and its regulation mechanism. Leaf traits directly affect the basic behavior and function of plants, which is closely linked to the plant growth strategy and the ability to use resources.Photosynthetic active radiation can significantly change the leaf morphological structure and physiological and biochemical characteristics during plant growth, plant leaf photosynthetic physiological and morphological characteristics(such as SLA, Pn, Tr, etc.) also reflects the plant growth strategy and resource use pattern, the leaf morphological structure and physiological and biochemical characteristics is the results of plant and environment long-term interaction, where in the light intensity on leaf size, specific leaf area, photosynthetic rate, transpiration rate and chlorophyll fluorescence characteristics has a significant impact. Many scholars respectively had studied that the leaves and twig different growth rate relationship, leaf size formation and adaptation mechanism, leaf photosynthesis and chlorophyll fluorescence characteristics, however, combing the leaf traits and photosynthetic characteristics to study the mechanism of interaction between the plant traits, resource utilization and allocation process of plant and adaptation strategies of and plant is not deep enough. In view of this, in flood plain wetland in Zhangye City, select different plant size Tamarix ramosissma as our research object. Total of 90 plants were divided into different size classes based on the volume: d(the cube root of plant volume) ? 90 cm, 90 cm < d ? 140 cm, and d > 140 cm. Twig and leaf traits were log-transformed, and the standardized major axis(SMA) estimation method was used to examine the allometric relationships of twig length with leaf area or leaf number. On the basis of plant twig an leaf traits and photosynthesis theory, we analysed twig and leaf allometric growth relationship, leaf area and net photosynthetic rate relationship, leaf area and water use efficiency relationship, and the leaf chlorophyll fluorescence characteristics. In order to systematically elaborate the strategy about plant resource allocation and response strategy to light environment, further enhancing the understanding of plant photosynthetic yield and adaptability mechanism. Results show:(1)Size I, size II and size III of Tamarix ramosissima photosynthetic effective radiation intensity are upper > middle > surface, photosynthetic active radiation in turn to decreased.(2)With the increasing of the plant size, Tamarix ramosissima height, twig number, twig length and leaf area in accordance with the size I, sizeII, sizeIII increased successively, but branching angle, specific leaf area and leaf number were gradually decreased.(3)Three size classes Tamarix ramosissima twig length and leaf area, twig length and leaf number showed a significant positive correlation, with increasing of twig length, leaf area and leaf number were increased. Allometric slope of twig length and leaf area was size I>size II >size III,but twig length and leaf number have the common slope of 0.90, compared with size III, the size I and size II SMA intercept of Tamarix ramosissima appeared significant positive movement the along the Y-axis.(4)Different plant size of Tamarix ramosissma net photosynthetic rate, water use efficiency, transpiration rate, stomatal conductance, and specific leaf area exist significant differences. Pn?Tr?Gs and SLA were < size II< size III, but the WUE was size I > size II> size III.(5)There was significant positive correlation relationship between the rate of photosynthesis and leaf area, and there was significantly negative correlation relationship between water use efficiency and leaf area. the regression slope of rate of photosynthesis and leaf area was size I <size II < size III, whereas, the regression slope of water use efficiency and leaf area was also size I <size II < size III.(6)Tamarix ramosissima chlorophyll fluorescence values of qP and Y(II) were size I > size II >size III, the NPQ, Y(NPQ) and Y(NO) were size I < size II <size III.Twig and leaf traits and their relationships, leaf photosynthetic characteristics are restricted by the plant size, due to the light resource constraints, twig length, twig number, leaf area and leaf number have investment difference and the leaf photosynthesis difference, the plant through the regulation of leaf traits and photosynthetic characteristics to adapt to the environment and to promote the photosynthesis efficiency. Different shapes and sizes of plants due to the ecological niche is not consistent, leading to its inevitable choice of different optimal income growth models, but also the ecological niche differentiation and compensating results.