Effect Of UV-B Radiation And Drought Stress On Morphology And Physiology In Artemisia Sphaerocephala

Arid climate,scarce precipitation,large temperature difference between day and night,intense ultraviolet radiation and sparse vegetation are the characteristics of desert area.As the pioneer of sand-fixation plant in desert area,Artemisia sphaerocephala could well adapt to the desert environment.In the long-term evolution process,A.sphaerocephala has formed a defense mechanism that can effectively resist the adverse situation of desert.A.sphaerocephala was used as research material in the present study.We simulated two universally abiotic stresses in desert region: UV-B radiation and drought,and conducted the combined treatment for 21 days.The aim of this study is to explore the effects of supplemental UV-B radiation on growth of A.sphaerocephala seedlings under drought stress with different gradients.The main results are as follows:(1)When adding UV-B radiation,as compared with drought treatment,some morphological indexes of A.sphaerocephala seedlings,such as leaf weight,stem weight,root weight,total biomass,leaf area,specific leaf area,plant height and root shoot ratio,were significantly increased.The result indicated that UV-B radiation could alleviate the inhibition of drought stress on the growth in A.sphaerocephala.(2)When adding UV-B radiation,the antioxidant capacity,relative water content of combined treatment were significantly increased;while proline content,relative conductivity and malondialdehyde content of combined treatment were significantly decreased when compared with drought treatment.It revealed that UV-B radiation could alleviate the physiological damage which caused by drought stress in A.sphaerocephala.(3)When adding UV-B radiation,the flavonoid content of UV-B stress + Light drought stress was significantly higher than Light drought stress,and the flavonoid content between UV-B stress + Severe drought stress and Severe drought stress had no significant difference.Phenylalnine ammonialyase,chalcone synthase and chalcone isomerase were three key enzymes in flavonoid synthesis pathways.The change of chalcone isomerase content was consisted with the change of flavonoid content,and chalcone isomerase may be the rate-limiting enzyme in flavonoid synthesis pathway of A.sphaerocephala.(4)Under the drought stress and UV-B radiation,the content of saturated fatty acids was increased,and the content of unsaturated fatty acids was decreased.Index of unsaturated fatty acid was reduced and the composition of fatty acids in membrane lipid tended to be saturated at the same time.Linoleic and linolenic were decreased significantly,which was caused by drought treatment.After adding UV-B radiation,polyunsaturated fatty acids content of UV-B stress + Light drought stress was higher than Light drought stress,and monounsaturated fatty acids content of UV-B stress + Severe drought was higher than Severe drought stress.The lipoxygenase activity of combined treatment was significantly lower than drought treatment.The results indicated that the maintenance of high level unsaturated fatty acids played an important role in adapting the compound environment of A.sphaerocephala.