| A comparative study on drought-resistant ability of three species of Caragana Fabr, Caragana microphylla, Caragana intermedia and Caragana korshinskii, were performed, using a method of PEG-6000-simulated drought stress.The levels of various phytohormones and Cu/Zn-SOD gene expression of three Caragana Fabr species at different growth periods were investigated, and the drought-resistant ability of the three species were discussed. The main results are as follows:1.The RWC of the three Caragana Fabr species gradually decreased by increasing of PEG-6000-treated time, while the NWSD showed an opposite tendency.2.The contents of phytohormones in the three Caragana Fabr species were determined. Under the drought-strees conditions, the contents of ABA and IAA increased, and the content of GA3 decreased in the three plant species. The contents of ABA and IAA in leaves of the three Caragana Fabr species increased during the growth period after germination, and then decreased, while the content of GA3 appeared a tendency of decreasing in the seedling stage.The Caragana microphylla had a higher contents and a faster increasing rate of phytohormones (ABA, and IAA) than those of the other species. These results indicated that phytohormones play an important role in drought-stress response and plant growth and development.3.Cu/Zn-SOD genes were isolated from the three Caragana Fabr species, and the Cu/Zn-SOD gene expression under drought stress conditions were investigated by RT-PCR. The results showed that the Cu/Zn-SOD gene expression in the three Caragana Fabr species were induced under the drought-stress conditions and the Caragana microphylla had a higher accumulation of Cu/Zn-SOD mRNA than the other species.These results suggest that the Caragana microphylla has a stronger drought-resistant ability than the other species.This study will prove a theoretical and experimental basis for protecting and utilizing of Caragana plants.
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