Responses Of Native Shrubs To Drought And Salt Stress In Urumqi

Salsola arbucula, Convolvulos tragacanthoides, A. traphaxis virgata, A. spinosa and Caragana acanthophylla are important component of vegetation around Urumqi. They play an important role in maintaining ecosystem stability in the area.The response to drought stress of S. arbucula, C. tragacanthoides, A. spinosa and A. virgata were studied with controlling water by potted planting.The results showed that the hight, basal diameter and the biomass of the four shrub species were differently decreased at three levels of drought stress.The distribution of the biomass were also affected. C. tragacanthoides were least decreased, and A. virgata were the most decreased. At the three level of drought stress, the contents of malondialdehyde (MDA), proline and solube sugar were higher than that in the control at different level, and the content of chlorophyll were contrary. Analysis by fuzzy membership functions, it showed that their drought resistance descending order was as following: C. tragacanthoides > A. spinosa > S. arbucula > A. virgataS. arbucula, A. virgata, A. spinosa and C. acanthophylla seedlings were studied with controlling salt by potted planting to research of their growth and physiological charcteristics. The results showed that compared with control, the growth and biomasse of A. virgata and A. spinosa were enhanced with mild salt treatment. At the same time, the growth and biomasse of S. arbucula and C. acanthophylla had no significant changes. The chlorophyll contents of A. virgata increased progressively with salt treatment, and had no significant effect on chlorophyll (a/b) ratio with moderate and severe salt stress. The proline contents of Salsola arbucula was the lowest of the four shrub species, and had not increased at the three salt stress levels. Proline and solube sugar play an important role in the osmotic adjustment of A. virgata and A. spinosa. And the osmotic adjustment of C. acanthophylla were mainly by solube sugar. Analysis by fuzzy membership functions, it showed that their salt resistance descending order was as following: A. virgata > A. spinosa > C. acanthophylla > S. arbuculaSeedlings of A. virgata and C. acanthophylla were grown in pots with varied soil drought and salt (NaCl) levels (alone and in combination) to determine their effects on the growth and biomass allocation of the seedlings. The results showed that there were significant effects of soil salt and water contents on symptoms and survival rate, the relative height growth, relative basal diameter growth, biomass and its allocation of the seedlings. According to the results we found that the two shrubs were acclimated moderate stress (drought, salt and their combination). The growth of seedlings displays intercrossing adaptability under mild intercrossing stress. C. acanthophylla were more tolerant to drought stress, but A. virgata were more tolerant to salt stress. C. acanthophylla grew better under intercrossing of drought and salt stress.As for physiological charcteristics of the two shrub seedlings under drought and salt stress, the results showed that the contents of osmo-regulation substances increased significantly, which played an active role on resistance. Because of the cell membrane lipid peroxidation, the MDA content in leaves of C. acanthophylla rapidly increased with increased salt concentration, as well as A. virgata under drought stress. With increasing of the stress,the leaf chlorophyll contents of the two shrubs decreased gradually. In a word, C. acanthophylla grew better under intercrossing of drought and salt stress.