| Black Locust(Robinia pseudoacacia)was headed for water and soil conservation species and play an important role in afforestation for its characteristics of combating drought and fast—growing. They are the main tree species in afforestation in the arid and hemi—arid areas. One—year—old seeding of ten Locust clones of 8048, Big Leaves, Little Leaves, 8041, Num2, Num7, Num9, Num5, 3—I and NC have been used as materials to study the characteristics of drought resistance for each tree species. The tested traits include the content of chlorophyll, photosynthesis rate, transpiration rate , water use efficiency, water potential of leaves(at dawn), leaves water content and relative water content, water consumption, water consumption rate, water loss rate, leaves soluble protein, leaves relative electric conductivity and the content of leaves MDA, analyzed by using subordinate function. The results were as follow:(1)The ability of combating drought is a complex hereditary and is controlled by many physiological and biochemistry characteristics. In drought gradient, by analyzing the these 13 indexes, we can conclude that the clones of 8048, Num7, 3—I and NC have stronger ability than Num2 and Num5 in combating drought. The ability in combating drought of Big Leaves, Num9, 8041 and Little Leaves is moderate. The drought resistance for the ten black locust clones was ranked as follows:3—I>8048>Num7>NC>Big Leaves>Num9>8041 >Little Leaves>Num2>Num5.(2)In the response of photosynthesis, photosynthesis rate and transpiration rate dropped with the decreasing of soil water content. The daily variation of photosynthesis rate were similar with two peak and had the phenomenon of "midday rest". There were one peak in the daily variation of transpiration rate and the peak of the clones of 3—I, 8048, Num5 and Num2 were at the noon. The water use efficiency increasing with the decreasing of the soil water content. The overall tendency of the content of chlorophyll were decreasing with the soil water content' dropping. But in the drought gradient, they displayed the tendency of increasing at first and decreasing at last. |
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