Physiological Responses Of Gymnocarpos Przewalskii Leaves To Natural Drought

Gymnocarpos przewalskii belongs to the perennial small shrubs,being a national first-class protected plant and the relatively rare tertiary relict plant distributed in the desert region of Central Asia,possessing an important scientific value in studying the origin of the xerophytic flora components.As one of the main constructive species in the stony desert area,it plays an important ecological role.Taking the leaves of Gymnocarpos przewalskii on the annual and perennial branches of big and small bush,analyzing the change and variation of the following physiological indicators among different months(June,July and August)and among different types of leaves under natural drought conditions,the physiological and ecological response characteristics and adaptive mechanisms of different types of leaves to natural drought and provide a theoretical basis and reference for further studying the physiological and ecological response mechanisms of Gymnocarpos przewalskii and its endangered causes under extreme drought conditions,and provide some reference for the rare species protection and vegetation restoration.The results showes as follows:(1)With the persistence of drought,UA’s Chla+b,Pro,SS,SOD,APX,AsA firstly increased then dreased,while TWC,Va/Vs,and Chla/b showed the converse change trend.POD and CAT activities were significantly enhanced,SP continued to accumulate,and REC and MDA contents continued to increase.The results showed that this type of leaf can adapt to certain droughts through the osmotic adjustment of proline and soluble sugars and the antioxidation of SOD,APX activitys and AsA content.Soluble protein is the main osmotic adjustment substance for adapting to drought,POD and CAT activities are Antioxidant key activitie.(2)SS content and SOD activity in UP decreased significantly,REC and MDA content increased significantly,Va/Vs,Chla+b,APX activity,and AsA content increased first and then decreased.TWC and Pro first decreased and then increased,Car content,SP content and CAT activity continued to increase,suggesting that it mainly adapts to arid environment through the osmotic adjustment of proline soluble protein and the antioxidant protection of carotenoid and CAT activity.(3)The TWC of LA decreased significantly,REC and MDA increased significantly,and the leaf membrane system was significantly damaged.Va/Vs,Chla+b,Pro,SOD,APX,and Car first decreased and then increased,then decreased.Chla/b,SP,SS,POD,CAT,and AsA showed a significant trend of falling first and then increasing,indicating that they could exert osmotic adjustment effects on soluble protein and soluble sugar by enhancing the synergistic action of photosynthetic activity,osmotic adjustment substances,antioxidant enzymes,and antioxidants.And POD,CAT and ASA antioxidant effect to reduce the damage of drought on the leaves.(4)The MDA content of LP increased significantly.The values of TWC,Va/Vs,Chla+b,Pro,SS,APX,AsA,and Car increased first and then decreased.Chla/b,REC,SP,and POD decreased first and then increased.The CAT activity was significantly increased,indicating that it mainly through the synergistic action of three osmotic regulators,and the combined antioxidant effect of APX,CAT,POD enzymes,and AsA,Car substances maintained the photosynthetic activity of the leaves,in which the CAT activitie was resistant to the leaves.Protection plays a key role.(5)Under the same rainfall conditions,in June,Pro,POD,CAT,and MDA contents of leaves in small shrubs were significantly greater(P<0.05)than those in large shrubs,and TWC,Chla/b,SP and Car were smaller than those in large shrubs and the difference was significant(P <0.05).(6)In July,the REC,MDA,SOD,POD,CAT,APX,and AsA of the small shrub were significantly larger than those of the large shrub(P<0.05),TWC,Va/Vs,Chla+b,Chla/b,SP,Car was significantly less than large shrubs(P<0.05).In August,the Va/Vs,Chla+b,Chla/b,Pro,POD,CAT,and Car of the small shrub were obviously larger than the big shrub(P<0.05),and the SOD was significantly smaller than the big shrub(P< 0.05).Under the same rainfall conditions,in June,the Va/Vs,CAT,APX,MDA of the leaves on the annual branches were larger than those on the perennial branches,while the REC,POD,Car were smaller than the perennial branches.In July,Chla/b,Chla+b,REC,SP,SOD,and Car of the leaves on the annual branches were greater than perennial branches.In August,Va/Vs,REC,MDA,Pro,SS,SOD,and POD activity of the leaves on the annual branches were greater than perennial branches,and CAT activity was less than perennial branches.(7)Comprehensive evaluation of drought resistant showed that in different months,the levaves showed different drought ability.In June,the order of drought resistance of different types of leaves was: LA>UA>UP>LP,In July,the order showed as: UA>LA>UP>LP and in August,the order was: UA>UP>LA>LP.Comprehensive analysis indicated that the drought resistance of leaves on annual branches was greater than that of perennial branches,and the drought resistance of the shrubs was greater than that on perennial branches and the drought resistance of the leaves on the small shrub was higher than that on the large shrub.As drought time continues,the final drought resistance of different types of leaves showed as: UA>LA>UP>LP.