The Physiological And Biochemical Responses Of Multiple Stress On Desert Plant Karelinia Caspia Less Bieb

This research used to gradient PEG-6000, NaCl solution concentration, and the high temperature tosimulate drought, salt, and high temperature stress. The seed germination rate, seedlings protectivemembrane permeability and lipid peroxidation degree (relative conductivity and MDA content), protectiveenzyme system (SOD, POD and CAT activity) and the change of chlorophyll content of composition inthe Karelinia caspia Less leaf statisticsed under above stresses were determined.The results showed that:(1) Under the5%~20%of PEG stress, the germination rate of Karelinia caspia Less seed was over50%.When PEG mass fraction in the range of20%~30%, it reduced sharply to11%. So, the critical value toresistant to PEG of Karelinia caspia Less seeds was20%. Under the drought stress of radicle, germ growthcharacteristics and similar as seed germination. The Karelinia caspia Less seedlings,which was stressed inthe range of PEG5%~15%, With concentration and stressestime of the PEG enhancing, the MDA content,activity of POD, SOD and CAT were increased with stress prolonged. But in this range, the chlorophyll a,chlorophyll b and content of chlorophyll (a+b) compared with each other were no significant difference.When the seedling stressed by25%PEG, relative conductivity and MDA content were increased with stressprolonged; POD, SOD and CAT activity increased with prolonged stress first decreases after.Thechlorophyll a and chlorophyll b and lower content of chlorophyll (a+b).(2) Under the salt stress of50~150mmol/L NaCl solution concentration,the seed germination rate wasabove50%;NaCl solution concentration in the range of200~300mmol/L of seed germination rateeventually fell sharply to8%,the critical value for NaCl stress of seed germination period was200mmol/L.The Karelinia caspia Less seedlings stressed under NaCl solution concentration in the range of200~300mmol/L,the MDA content, POD, SOD and CAT activity increased gradually with prolongedstress,when the NaCl solution concentration was in the range of400~500mmol/L, divided by the SOD,MDA content, POD and CAT activity first increased after fell with prolonged stress;The chlorophylla,chlorophyll b and total chlorophyll content as the stress time extended gradually reduced.Therefore,Karelinia caspia Less seedling biofilm for salt stress of tolerance limit was300mmol/L;Karelinia caspiaLess seedlings of protective enzyme system of SOD for salt stress of endurance limit was400mmol/L,PODand CAT of salt stress endurance limit was300mmol/L; Karelinia caspia Less seedlings chlorophyll NaCltolerance threshold was400mmol/L.(3) The most suitable temperature of germination of Karelinia caspia Less seed was20/25℃.Kareliniacaspia Less seedling protective membrane permeability and lipid peroxidation degree,under40℃,45℃and50℃stressed,MDA content for heat resistant to high temperature time threshold was6;8h and3h. TheSOD and CAT activity of Karelinia caspia Less seedling increased and POD activity increased first, after inwithin24h,12h and24h to heat threshold of activity with stress prolonged at40℃,;Under45℃stressed,the enzyme activity of SOD, POD and CAT, was first raised and after reduced with stress time extending,and reached the limit value at8h,4h and8h;under high temperature of50℃stressed, the enzyme activityof SOD, POD and CAT was raised before reduced with stress time extended, and activity reached the limitvalue in1h.Above all,the PEG, NaCl and high temperature resistance of Karelinia caspia Less seeds was notstrong,through the seedlings analysised in PEG, NaCl and high temperature stress, determined Karelinia caspia Less seedling drought tolerance limit was PEG20%, salt stress endurance limit was400mmol/L; thelimit value of the resistance for high temperature was45℃.