Comparative Study On Anatomy Structure And Photosynthesis Characteristics Of Several Arbor Leaves Of Qinghai-Tibet Plateau

The characteristics of leaf structure and photosynthesis of 4 Salicaceae species Populus szechuanica var.tibetica,Populus alba L.,Salix maizhokunggarensis and Salix paraplesia var. subintegra were examined in the different altitudes habitat at Qinghai-Xizang Plateau,in order to study the adaptability of plant to plateau environment change.The results showed that the thickness of leaf,layers of palisade cells,and thickness of upper and lower epidermis cuticle,density of the first layer cells of palisade cells,density of stoma and thickness of midrib of the four species were significantly increased,except the area of stoma was significantly decreased.But there are no significantly effect in the type of leaf,shape and arrangement of epidermis and palisade cells and interspaces of cells with increasing altitude. However,there are mutual characteristics for 4species of Salicaceae.The response to the environment change of species in Populus mainly depend on keratose,while species in Salix rely on fibrovascular.Moreover,the photosynthesis characteristic of the 4 arbor were taken on disciplinary change.P_n,G_s and C_i of the leaves from four species-were significantly decreased with the increasing altitude.On the contrary,the L_s was significantly increased.The result of data analyzed indicated that there were similar adaptation strategies among the 4 species in Salicaceae along the plateau habitat change of them,the leaf structure changed and the ability of carbon assimilation decreased to adapt the plateau habitat.But there still exist difference.Except Populus szechuanica var.tibetica,intracellular CO₂ concentration(C_i) in the other three arbor species was significantly higher at Lhasa than at Naqu;stomatal inhibition(L_s) of them was significantly lower at Lhasa than at Naqu. The two above parameters showed no difference between Lhasa and Naqu in Populus szechuanica var.tibetica.As to Populus szechuanica var.tibetica,non-stomatal inhibition was the main reason for decline of photosynthesis.About Salix maizhokunggarensis,some nontemperature factors might have been involved in the decline of stomatal conductance which leads to stomatal inhibition.Therefore,we can conclude that different arbor species have different ways in responding the environment of Qinghai-Tibetan Plateau while the specific mechanisms of this response need to be more investigate.