Study On Ecophysiological Characteristics Of Narrow Leaves And Broad Leaves Of Populus Euphratica

P. euphratica is the only tree species in dry desert that can form large natural forests, which is very important in ecological and economical construction in temperate deserts. The leaf types of the sapling of P. euphratica are mainly lanceolate leaves and linear leaves, and we call the two types altogether as narrow leaves. While the leaf types of the mature tree are nephroid leaves and broad-ovate leaves, and we call them broad leaves. With the idea of ecophysiology, we have studied the narrow leaves and broad leaves of P. euphratica in deferent tree age in Ejina County at three aspects:①Phenology,②Drought resistance: PV curve and cut branch method,③photosynthetic property. Some conclusions have been drawn as the following. 1) The narrow leaves and the broad leaves have respectively different strategies of leaf life history. The strategies of broad leaves are earlier leaf emergence in spring, short duration of leaf emergence and earlier defoliation in autumn. The leaf emergence time of narrow leaves is later about 5 days than broad leaves. And its duration period of leaf emergence is very long. Defoliation time of narrow leaves in autumn is about 5 to 10 days later than broad leaves. The leaf number per current branch of narrow leaves is larger than broad leaves. 2) The ability of drought resistance of broad leaves is better than that of narrow leaves. And the two types of leaves have different drought resistance methods. The capacity of reduction of water loss of broad leaves is better than that of narrow leaves. Broad leaves contain more osmotic solute in the cell, and the ability of conserving water and tolerating low osmotic potential is better than which of narrow leaves. Narrow leaves maintain turgor pressure mostly by good elasticity of cell wall. 3) The ability of photosynthesis of broad leaves is better than that of narrow leaves. The LCP and LSP of narrow leaves is respectively 26.69μmolPhoton·m-2·s-1 and 448μmolPhoton·m-2·s-1, and broad leaves, 31.20μmol Photon·m-1·s-2 and 785μmolPhoton·m-2·s-1. Narrow leaves can tolerate much shadier condition than broad leaves. Broad leaves can adapt to intense irradiation. Therefore, the two types of leaves have different methods to adapt to the environment, that is, the characteristics of narrow leaves secure the fast growth of the saplings of P. euphratica and the settling of its population, and broad leaves secure its long-term survival in the deteriorating environment.