| Populus bachofenii×P. pyramidalis ROZ is a new cultivar hybridized by Populus bachofenii and P. pyramidalis, which is selected and cultured by scientists of Siberian arboretum in Russia. This cultivar has the characteristic of high adaptability, rapid growth, long life, beautiful shapes of trees and leaves, excellent timber and also the tolerance of low temperature (the lowest of -50℃), drought, and saline-alkali, which is suitable for city virescence and timber in north of China and other high altitude area. We validated the cold tolerance of Populus bachofenii×P. pyramidalis ROZ by carring out the field experiment for living through the winter, the plants were all survival, but the range of drought tolerance and salt tolerance were unknown. We should find out the capbility of drought and salt tolerance and their indexes in order to extend the variety in the areas that of drought, cold and salt.We used 1 year old tissue-culture derived seedlings of P. bachofenii×P. pyramidalis ROZ as material, determined seedling height, ground diameter, biomass, photosynthesis, permeation of plasma membranes, soluble sugar, soluble protein, SOD, POD, CAT under drought stress and salinie-alkali stress. The results were as follows:Drought stress and salinie-alkali stress had inhibitory effect on the growth of seedlings, which increased along with increasing of stress and the time prolong. The change of root/shoot ratio are different between drought stress and salinie-alkali stress. Root/shoot ratio in drought stress treatment are higher than that of control. The relative soil moisture of best growth condition is 60%～65%, and the absolute cubage moisture content of that is 27.6%～30.0%. Effect of salinie-alkali stress on seedling growth is low when the salinie-alkali content is lower than 0.2%.Drought stress and salinie-alkali stress depressed the net photosynthetic rate, transpiration rate and stomatal conductance of seedling and the depression enhanced with increasing of stress. The net photosynthetic rate is lowest under high stress of drought and salinie-alkali, which reduced by 91.70% and 61.67% respectively. The depression of net photosynthetic rate at initial stage of stress was caused by stomatal factor when the relative soil moisture is lower than 40% and the soil salinie-alkali content is higer than 0.4%, but at mid and later stage of stress were caused by non-stomatal factor.Membrane permeability enhanced by drought stress and salinie-alkali stress, and also increased the damage of cells. SOD, POD activity increased along with increasing of stress and the time prolong. The enzymes activity didn't decrease in the two stresses suggested that P. bachofenii×P. pyramidalis ROZ has higher self-regulated and adaption capability. SOD, POD and CAT can prevented the damage of radical efficiently. P. bachofenii×P. pyramidalis ROZ can start the osmotic-regulation mechanism after stressed by drought and salinie-alkali, and then depressed cell osmotic pressure through regulating by soluble sugar and protein, which can also absorbd water from soil and maintain normal metabolism. Soluble sugar content increased at initial stage of both the two stresses, but decreased at later stage especially in high stress, which related with the leakage of cytoplasm caused by membrane permeability. The soluble protein content appeared to decrease at initial and then increase which suggested that drought stress and salinie-alkali stress affected the protein synthesize. But at later stage of stress, the soluble protein content increased because the drought tolerance genes and salinie-alkali tolerance genes were activated.The results showed that P. bachofenii×P. pyramidalis ROZ could grew well with soil moisture content above 18.4% and the best growth condition of soil moisture coontent 27.6%～40.0%. The P. bachofenii×P. pyramidalis ROZ could survive and grow well with soil salinie-alkali content below 0.2% , survive with soil salinie-alkali content below 0.2%～0.4% and could not survive with soil salinie-alkali content above 0.4% .
|
PDF Full Text Request