Study On Physiological Characteristics Of Drought Resistance In Ailanthus Altissima Seedling

The tree of heaven (Ailanthus altissima Swingle) is one of the main forestation and urban planting tree species, which has a fast-growth, wide distribution and adaptability characteristics. This paper studied the physiological response of A. altissima in seedling stage to soil drought stress with four different soil contents levels: W1(12.5% of well-watered treatment), W2(25% of well-watered treatment),W3(50% of the well-watered treatment),W4(75% of soil water content under well-watered treatment, CK), and evaluated the drought resistance of the tree of heaven. The main results are as follows:(1) Under the soil drought stress in pot-cultivation condition, the changes of the membrance permeability, chlorophyll content and MDA content of the seedlings of Shandong Luzhong and Henan Baofeng provenances were smaller, and the leaf water potential of the provenances were small, but POD activity and net photosynthesis were high, which indicated that the seedlings of these two provenances have the characteristics of drought resistance. However, the leaf water potential and net photosynthesis of the seedlings of Ningxia Pingluo and Beijing Miyun provenances were high and net photosynthesises were small. Therefore, the rank of drought resistance from strong to weak for the seedlings of different provenances are: Shandong Luzhong and Henan Baofeng, Ningxia Pingluo, Beijing Miyun and Fraxinus americana L.(2) As the increasing of soil drought stress, the membrance permeability, POD and SOD activity, MDA content were increased, but the chlorophyll content, net photosynthesis were reduced. The increasing of the height and root-collar diameter of seedling with the treatment of sever and moderate drought stress were 13% and 21% of well-watered treatment respectively. The seedling's drought tolerance level was between moderate and mild drought stress.(3) Under pot-cultivation and greenhouse condition, the peak of daily water consume of the seedlings occurred at 12:00pm to 16:00pm. The value of daily water consume for the seedling of Fraxinus americana L. was biggest than others which was 80g per individual, but the value of daily water consume for the seedling of Henan Baofeng provenance was smallest which was 50.8g per individual. The daily water consume was reduced largely when the soil water content was reduced, but the reducing of daily water consume for the seedlings of Shandong Luzhong and Henan Baofeng provenance were smaller.