The Relationships Among The Leaf Traits Of Polygonum Viviparum In Different Population Densities In Gaihai Wetland

Plant leaf was the main organ and tissue of plants,and the relationship among leaf traits were most sensitive to the changes of external environmental conditions.The allometric growth relationship between leaf and vein traits was the basis of the theory of leaf economics spectrum,and have affected water use strategy of plant physiological activities,which is helpful to understand the economic tradeoff between the carbon input and the function of leaf vein.The correlation between petiole length and vein traits have affected hydraulic dynamic balance of leaves,which has the vital significance to reveal the plant leaves water transport safety and effectiveness in the process of the coupling mechanism of physiological ecology.The coevolution of leaf veins and leaf index were the basis for understanding the theory of plasticity in plants,which was important to regulate the physical structure of plant leaves and the relationship of physiological metabolism in the press living environment.In this paper,The relationship between the leaf size?leaf thickness,leaf area?and tiny vein density,and the relationship between the petiole length and vein traits?tiny vein density,middle vein diameter?,and the relationship between the leaf index and vein traits of Polygonum viviparum population in different density habitats in Gahai alpine meadow wetland was studied by using correlation and standardized spindle estimation method?SMA?,according to the plant population density,the Polygonum viviparum population were divided into three density gradients,high density(I,>330 plant·m^–2),medium density(II,160–330 plant·m^–2)and low density(III,<160 plant·m^–2).The biomass allocation patterns and resource utilization strategies of the wetland plants under different heterogeneous environments were analyzed.It shows that wetland plants can optimize the allocation of resources and the mechanism of phenotype plasticity according to their functional requirements.The results show:?1?There were significant differences in wetland community characteristics between different plots?p<0.05?.With the decrease of the density of the population of Polygonum viviparum,the soil water content,community hight and coverage gradually increased,the soil density,soil electrical conductivity and PAR?photosynthetically active radiation?decreased.the density of the population decreased first and then increased?p<0.05?.?2?With the decrease of the density of the population of Polygonum viviparum,there were significant differences among leaf traits and plasticity index in different density plots?p<0.05?.the leaf area,leaf width and tiny vein density of Polygonum viviparum were significantly increase,and the leaf thickness,leaf length,middle vein diameter,petiole length and plant height were gradually decreased.?3?The photosynthetic parameters of Polygonum viviparum were significantly different?p<0.05?.With the decrease of the density of the population of Polygonum viviparum,the transpiration rate?T_r?and the saturated vapor pressure deficit?VPD?decreased gradually.The net photosynthetic rate?P_n?and and water use efficiency?WUE?of the Polygonum viviparum population firstly increased then decreased.The correlation between leaf traits and photosynthetic parameters of Polygonum viviparum was significantly different?p<0.05??4?The correlation between leaf area and leaf thickness and leaf density of Polygonum viviparum was significantly different?p<0.05?.There was a significant positive correlation between the leaf area and the density of the veins in the high density???,medium density???and low density???.The SMA slope gradually increased with the decrease of population density.The leaf thickness and the density of the veins were significantly negatively negative in the three density habitats?p<0.05?.The SMA slope gradually decreased with the decrease of population density.?5?The relationship among the petiole length and middle vein diameter and tiny vein density were significantly different in different wetland populations?p<0.05?.There was a significant negative correlation between middle vein diameter and petiole length in high density???,medium density???and low density???.SMA slope gradually increased with the decrease of population density.And there was significant difference between the two groups?p<0.01?.The slope of SMA showed a tendency to increase gradually with the decrease of population density.?6?The correlation among the middle vein diameter and tiny vein density and leaf shape index were significant?p<0.05?.At the high density???and low density???plot,The correlation between middle vein diameter and tiny vein density,leaf shape index and tiny vein density were very negative significant?p<0.01?,medium density???showed significant negative correlation?p<0.05?.At the same time,There was a significant positive correlation between the leaf shape index and the middle vein diameter of the low density sample?p<0.01?in the high density plot??,??,and there was a significant positive correlation between the medium density plots?p<0.05?.The growth relationship between leaf traits and plant was closely related to the acquisition and utilization of resources,which could reflect the adaptability of its physiological activity and leaf shape shaping and growth law to the environment.The intense sun radiation,water salt and other stress conditions have led Polygonum viviparum to selected the middle vein,low tiny vein density,and long petiole of the hydraulic ecosystem,and the small,thick,elongated blade configuration at high density habitat of wetland community,which could make sure that the plants themselves keep their carbon and water balance and guarantee the optimal coupling between plant leaf and physiological function in heterogeneous habitat.In low density plots,facing with low physical activity and the intense competition for resources in the community shade environment,the leaf hydraulic support structure were combined by short petioles,coarser middle vein and a large amount of tiny vein were chosed by Polygonum viviparum population,and formed the physical build pattern of large,thin oval blades.Therefore,it can be restricted to cold and cold and maintain high water use efficiency in the body by reducing the risk of the xylem to improve water conductivity.