Study On Leaf Development And Leaf Characteristics Of Populus Euphratica In Ejina County, Inner

Populus euphratica is a relict plant from Tertiary, with strong drought resistance and salt tolerance. As the constructive species in Ejina oasis, Populus euphratica has important ecological significance to the function of ecosystem in this area. Populus euphratica is a typical plant species with heteromorphic leaves, the leaves of a mature tree are consist of variety shapes such as acicular, lanceolate, ovate and broad ovate. Leaves traits of Populus euphraticais can indicate physiological and ecological characteristics and environmental adaptation. Research of development of different shapes of leaves and leaf traits can reveal the development law and resource allocation features in assistant. And it will learn more about survival strategies to climate change adaptation in progress. For a systemically study of stress-resistance of Populus euphraticais, which shows theoretical and practical significance.Our objectives were Populus euphratica in Ejina, Inner Mongolia. The research aimed at the leaves of different stages of developmental, which included lanceolate, ovate and broad ovate leaves. The main results were as following:Comparative and analysis of structural characters in different developmental stages of Populus euphratica leaves had found that:there were differences between the three structural characters in three shapes, and the difference changed with the growth of leaves. That is to say, throughout the process, leaves characters (lamina water content, lamina mass, lamina area and lamina volumes) and petiole characters (petiole length and petiole mass) were always significantly different between broad ovate leaves and lanceolate leaves. Lamina water content, lamina mass, lamina area and lamina volumes in three type leaves at different developmental stages were significantly correlated. The relationships of growth in traits varied from leaf types, so as to the growth index with leaf growth. Laminas and petioles trait were significant correlated, and relationships variability existed between different characters of leaf types and petiole growth characteristics.In different development stages, the water physiology results of three leaf types showed:Leaves transpiration rate (Tr) and water usage efficiency (WUE) trends varied at different developmental stages, The Tr of July was higher than the May, and the WUE was on the contrary slightly.In the three-shaped leaves functional traits, photosynthesis diurnal variation of three leaf types showed:On daily net photosynthetic rate per area (Aarea), the May was higher than the July, but the relation turned over on net photosynthetic rate per unit mass(Amass). Light response curve results showed that the Aarea of lanceolate leaves significantly lower than the broad oval, while no significant difference was found on Amass of three leaf types. The respiration rate of lanceolate leaves, Dark respiration rate (Rn) of mitochondrial respiration rate in light (RL), was significantly lower than the broad ovate leaves. As carbon balance of blade was weight by both photosynthesis and respiration, different leaf type did not have a significant difference on carbon assimilation efficiency (Ag/R), but lanceolate leaves ratio of Ag/R higher than broad ovate leaves. Lanceolate leaves have a high Ag/R and photosynthetic nitrogen use efficiency (PNUE), and broad ovate leaves have a high Aarea and respiratory rate.By analyzing these findings, the conclusions drawn as following:Populus euphratica leaves formed disparately at different growth stages, which had a close relationship on adapting to the special environmental conditions. There are differences among different leaf structure traits, and the difference with the development changed.No significant difference on fixed resources (carbon and biomass) of leaves there was, but on different levels, allocation of resources and the allocation ratio do exist. Broad ovate leaves exhibited high-energy capture and high-energy consumption on functional characteristics. And resource allocation on the structure traits were higher than the lanceolate leaves. As it is to say broad ovate leaves had a stronger resistance than the lanceolate leaves relatively. Based on the physiological needs of different developmental stages of blades, investment ways and its ratio of structural traits and functional traits will be adjusted for three leaf types. A higher resource utilized in a period of strong growth (May) for lamina area, lamina biomass, lamina volumes and other structural traits aiming at supporting and improving resource capture and conversion efficiency to meet the needs of the blade vigorous physical activity. In mature leaves (July), resources are more allocated for improving the mechanical support and transporting efficiency of nutrient and water on petiole, which can enhance blade stress-resistance.