Effects of Drought Stress and Rehydration on Growth,Physiological Characteristics and Accumulation of Secondary Metabolites in Astragalus Mongholicus Seedlings
In order to clarify the response mechanism of Astragalus seedlings to drought stress with different water deficit degree,the effects of different drought stress degree,stress duration and rewatering on the growth,physiological characteristics and secondary metabolites accumulation of Astragalus seedlings were studied using Tongqi 16-1 seedling as experimental material.The results showed that mild drought stress treatment and moderate drought stress treatment for four,eight days showed a gradually decreasing trend in the plant height,aboveground biomass,chlorophyll content,and net photosynthetic rate of Astragalus seedlings with the deepening of stress degree and prolongation of stress time.The root length,underground biomass,the activities of superoxide dismutase and peroxidase,the content of malondialdehyde(MDA)and proline(Pro)gradually increased,and a large accumulation of secondary metabolites in the roots was observed.After 12 days of moderate drought stress,the accumulation of secondary metabolites decreased significantly,and the change trend of other indexes were basically the same as that of four and eight days of moderate drought stress.Under severe drought stress,the contents of MDA and Pro in Astragalus seedlings continued to increase,while the other indexes decreased gradually.After rehydration,the indexes of mild and moderate stress were basically restored to the control level,while those under severe stress could not recover completely and there were significant differences between the seedlings and the control group after long treatment.The results showed that Tongqi 16-1 seedlings had certain drought resistance,according to the comprehensive analysis of seedling growth,physiological and biochemical indicators,the relative water content of soil water that did not affect the growth and development of seedlings was 50％-60％,and the stress duration was no more than eight days.
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