Study On Eco-physiological Responses Of Salix Matsudana On Drought Stress

Salix matsudana species was chosen as the research object, growth status, photosynthetic characteristics of leaves, water characteristics, osmotic adjustment substances and protective enzyme activity in a 10-day cycle for the measurement and analysis to drought were studied systematically via pot experiment referring to control group, light drought stress, moderate drought stress, and severe drought stress, among which control group stranded for 90% field capacity 44.39%, light drought stress stranded for 70% field capacity 44.39%, moderate drought stress stranded for 50% field capacity 44.39%, and severe drought stress stranded for 40% field capacity 44.39%.Through the research on response mechanism of Salix matsudana species under different drought stress conditions, theoretical basis was proposed for the further study on diversity of the methods of plants' resistance to drought, and reference for tree species selection in arid and semiarid area was provided.The research results showed that growth rate of Salix matsudana decreased, whose growth in thickness in caudex was inhibited and grew slowly under moderate and severe water stress. Through auto-regulation of Salix matsudana, photosynthetic growth and transpiration water consumption were decreased by reducing leaf number, narrowing leaf area, decreasing color intensity of leaves, and leaf wilting to be adapt to arid environment.The net photosynthetic rate and stomatal conductance both declined with the intensification of drought stress degree. In addition, light compensation point ascent and light saturation point descent through auto-regulation of Salix matsudana itself. Efficiency of apparent quantum yield dropt to be adapt to arid environment. Under different gradients of water stress, transpiration rate of Salix matsudana species all exhibited first elevation and then reduction as the light intensity enhanced. With the aggravation of water stress, the whole transpiration rate of Salix matsudana species decreased. Under each gradient of water stress, increasing amplitudes of water use efficiency were successively moderate water stress, light water stress, control group, and severe water stress, respectively as light intensity increased. It was indicated that under the circumstance of soil drought, photosynthesis of Salix matsudana species was conducted by using limited water in soil to maintain higher photosynthetic capacity and normal growth.When the time of drought stress prolonged and degree of drought stress intensified, water loss rate of Salix matsudana leaves increased and water retaining capacity of Salix matsudana leaves decreased. As the degree of drought stress intensified, increase amplitude of water loss rate was relatively low, which indicated that Salix matsudana species had relative high water retaining capacity and relatively great resistance to drought. Critical saturation deficit of Salix matsudana species ranged between 66.50% and 78.61%. As the degree of water stress intensified, water saturation deficit increased to consolidate resistance to drought through auto water regulation of Salix matsudana species itself in order to be adapt to disadvantageous habitat and to guarantee smooth growth consequently. Survival potential of Salix matsudana species was relative great under the circumstance of light water stress and moderate water stress.The soluble protein content of Salix matsudana species leaves increased gradually as the degree of drought stress intensified and time of drought stress prolonged to restrain more water. When subjected to light water stress and moderate water stress, SOD and POD enzyme activity in Salix matsudana body can be improved effectively to perform the function of protecting membrane system. However, when subjected to sever drought stress, the disequilibrium of generation and disappearance of superoxide occurred and SOD and POD enzyme activity in Salix matsudana body decreased, which were still higher than that of control group, though. MDA content and relative permeability of membrane in Salix matsudana leaves both increased as the water stress increased. Finally MDA content and relative permeability of membrane exhibited positive correlation.