Responses Of Photosynthetic Characteristics And Antioxidant System Of Indocalamus Decorus To Drought And High Temperature Stress

In this paper,the seedlings of Indocalamus decorus were used as experimental materials,and the artificial climate box was used to artificially simulate natural drought and high temperature stress.Set two temperature gradients:normal temperature treatment T1(28°C/22°C),high temperature treatment T2(40°C/28°C),and four moisture gradients under each temperature gradient:control drought(CK),mild drought(LD),moderate drought(MD),severe drought(HD).The photosynthetic fluorescence index and the relevant indexes of the antioxidant system were measured,and the drought resistance and heat resistance were evaluated,in order to provide a theoretical basis for the future research on the resistance to high temperature and drought.Below are key research findings:1.In order to adapt to the adversity,the Chl t of the leaves of I.decorus increased under high temperature and mild drought,and the contents of Chl a,Chl b,Chl t and Car began to decrease under moderate drought stress and mild coordinated stress.Under severe drought,they were significantly lower than the control 35.90%,31.10%,34.79%and31.85%.Under severe synergistic stress,they were significantly lower than the control by32.97%,30.57%,32.35%and 44.45%,respectively.It may be due to water shortage in leaves,and the combined effects of high temperature and drought have restricted the formation of photosynthetic pigments and the decomposition rate is greater than the synthesis rate.And Chla/b decreased under severe synergistic stress,and the core complex was damaged.2.Both drought stress and coordinated stress reduced Pnmax and photosynthetic capacity.The moderate and severe drought stress and high temperature drought coordinated stress decreased AQY and LCP,lowered the conversion efficiency of light energy,and reduced the ability to adapt to light.Drought and high temperature stress can adapt to adversity by reducing Tr and Gs.In mild to moderate drought,Pn and Ci decrease but Ls rises.The main factors leading to the decline of photosynthetic rate of I.decorus are stoma limitation and WUE increase in moderate drought.Severe drought and moderate to severe synergistic stress decreased Pn,Ci increased significantly,and Ls decreased significantly.The main factor turned to non-stomata restriction,WUE decreased significantly,and the photosynthetic mechanism of I.decorus was damaged.3.I.decorus copes with high temperature and drought stress by shutting down some reactive centers,increasing absorption and capturing light energy and using more energy for heat dissipation.In severe drought,V_J,Mo and DI_O/CS_Oare higher than CK by24.18%,42.05%and 27.10%,respectively.Under severe synergistic stress,it is 41.52%,86.58%and 31.55%higher than that of CK,but the energy used for electron transfer decreases from moderate drought and synergistic stress.Severe synergistic stressφEo is41.55%lower than CK,electron transfer is blocked,andψo is lowered.Severe drought stress and severe synergistic stress decreased by 27.60%and 38.65%,respectively.The carbon assimilation capacity of I.decorus began to decline.Under severe synergistic stress,ABS/CS_O,TR_O/CS_O,DI_O/CS_O,DIo/RC increased significantly,and ET_O/CS_Oand ETo/RC are significantly reduced.Although they absorb and capture a large amount of light energy,the energy used for electron transfer is drastically reduced,and the leaves of I.decorus are seriously damaged.4.I.decorus regulates cell osmotic potential by increasing the content of soluble sugar and soluble protein to resist drought stress.However,due to lack of water in moderate to severe droughts,the rate of hydrolysis of sucrose into glucose and fructose is slightly reduced,and the soluble sugar,sucrose,fructose and glucose under mild synergistic stress are significantly lower than drought stress by 40.28%,72.44%,55.35%and 41.07%.I.decorus waited for the adversity to be relieved by reducing its metabolism.The content of soluble sugar,sucrose,fructose and glucose increased significantly under moderate synergistic stress,but the content of soluble sugar and fructose was lower than that of moderate drought by 18.38%and 19.14%.It is possible that the interaction of drought and high temperature at this time inhibited the synthesis of soluble sugar and fructose.The relative water content of leaves under severe synergistic stress was 59.6%lower than that of CK,and the content of soluble protein and soluble sugar increased by18.19%and 15.78%respectively compared with severe drought.Compared with drought stress,more soluble sugar and protein are required to maintain osmotic potential.5.I.decorus can prevent excessive accumulation of ROS under mild drought by improving GR activity and GSH/GSSG value.I.decorus clears ROS under moderate drought by coordinating glutathione cycle and SOD and CAT activity.Under severe drought stress,the activities of SOD,CAT and POD increase,but GSH/GSSG is 56.40%lower than CK,glutathione redox is unbalanced,MDA content and relative conductivity are significantly higher than CK by 44.53%and 82.93%.The I.decorus leaves are damaged.In moderate synergistic stress,in response to the production of more ROS,the activities of SOD,CAT and POD increase by 108.99%,380.40%and 26.38%,but the efficiency of As A-GSH Cycle is not as good as that of mild synergistic stress.APX,DHAR and MDHAR activities are 19.21%,25.13%and 44.72%lower than mild synergistic stress,respectively.In severe synergistic stress,the activity of POD is partially inactivated or destroyed.Compared with CK,the activities of APX,DHAR and MDHAR are reduced by46.12%,16.05%and 62.19%,respectively.The ascorbic acid metabolism pathway is blocked,and GSH/GSSG is reduced by 68.18%compared with CK.Glycine redox is seriously imbalanced,the content of MDA and relative conductivity are increased by84.31%and 122.97%compared with CK,and the leaves of I.decorus are seriously damaged.To sum up,there are differences in the pre-adjustment methods of I.decorus under high temperature stress,drought stress and cooperative stress,but they can all adapt to adversity through their own adjustment.Moderate synergistic stress still has certain resistance and can be further domesticated and promoted as an ornamental bamboo species or slope protection plant in garden applications.In daily cultivation and maintenance,water should be added in time under continuous high temperature environment to avoid the combined effect of high temperature and drought to cause irreversible damage to the bamboo.