Effects Of Drought Stress On The Growth And Physiological Characteristics In Sorbus Folgneri Seedlings

Using a movable rain shelter to keep of precipitation,field experiments on the morphological and physiological-Biochemical characteristics of Sorbus folgneri.were conducted under different soilmoisture treatments by controlled irrigation,the relative soil moistures for the different treatments were controlled at 75%-85%(control),60%-65%(light stress),45%-50%(moderate stress),30%-35%(heavy stress).The purpose is to research for morphological characters, physiol-ogy and biochemistry characters under different stress levels of Sorbus folgneri.Investigate the initial adaptation mechanism to water stress and ability to understand the scope of its water needs and adapt to,provide the scientific basis for the introduction and cultivation of trees, the results as follows:1,Drought had significantly reduced seedling height, diameter, leaf area, increased main root length and lateral root number. Drought decreased biomass accumulation, altered biomass allocation patterns, led more photosynthetic products transferr to belowground parts, caused higher root to shoot ratio for the decreasing of stem and leaf mass ratio, and increasing of root mass ratio. However, this distribution is reduced at the expense of 1 stem and leaf mass ratio.2,With the enhanced level of drought stress, Sorbus folgneri leaf thickness, palisade tissue thickness was significantly thinner in the water sufficient conditions (control group), lime leaves Sorbus longer palisade tissue, arranged in neat rows, but under the moderate and severe drought conditions, the shorter the palisade tissue is small, the organizational structure under mild stress conditions the tightness of the largest, arranged in palisade tissue more closely, the plants use light energy the higher the efficiency. Severe stress treatment of leaf tissue structural organization of the tightness is smallest.3,Under drought stress, photosynthesis of Sorbus folgneri lhas been significantly affected, moderate, and severe stress of Sorbus folgneri photosynthetic rate, transpiration rate, stomatal conductance decreased significantly, but the intercellular CO2 concentration was higher than control; with water stress the degree of enhancement, lime seedlings stomatal limitation of photosynthes is has gone from non-stomatal limitation to the process of change, but mainly non-stomatal limitat.4,With drought stress intensity increasing and duration extension, leaf relative water content maitain stably in control and light stress, but reduce continually in moderate and heavy stress,and both soluble sugar content and malonic dialdehyde content increased remarkably. Meanwhile, moderate and severe stress on SOD, POD activity first increased and then decreased, indicating a long period of drought stress is beyond the tolerance range of Sorbus folgneri, so activity decreased.