Effects Of Suaeda Salsa Endophyte On Carbon And Nitrogen Metabolism And Chlorophyll Fluorescence Of Rice Seedlings Under Pb Stress

With the development of modern industry,heavy metal pollution in the soil is becoming more and more serious,seriously endangering the growth of crops and people's food security.Rice is an important food crop in China,and it is of great significance to study measures to improve its resistance to heavy metals.In this study,rice?Liaoxing No.1?was used as the material to infect rice with Suaeda endophyte EF0802.The endophyte infestation group under stress of different concentrations of heavy metals?0,50,100,150,200?M?Analysis of rice carbon metabolism?including carbohydrate content and key enzyme activities of carbon metabolism?,nitrogen metabolism?nitrate nitrogen content and key enzyme activities of nitrogen metabolism?and chlorophyll fluorescence parameters in the uninfected group,aiming at physiological and biochemical and chlorophyll fluorescence To explore the physiological mechanism of endophyte to improve the resistance of rice seedlings to Pb stress,and provide theoretical data for the future use of endophyte to improve the resistance of plants to abiotic stress.The main findings are as follows:1.Pb stress inhibited the plant height and root length of rice seedlings,and reduced the accumulation of dry and fresh weight above and below ground;endophyte infections significantly promoted the plant height,root length,and fresh weight of underground rice seedlings.2.With the increase of Pb concentration,the soluble sugar content of rice seedlings showed a trend of increasing first and then decreasing,and the content of sucrose,starch,cellulose and key enzymes of carbon metabolism showed a decreasing trend;endophyte infection significantly increased Pb stress The above sugar content of rice seedlings and the activity of key carbon metabolism enzymes indicate that endophyte infection can enhance the activity of key carbon metabolism enzymes to increase carbohydrate accumulation and alleviate the harmful effects of Pb stress.3.With the increase of Pb concentration,the nitrate nitrogen content of rice seedlings and the activities of glutamate synthetase?GOGAT?and glutamate dehydrogenase?GDH?gradually decreased,but the activity of glutamine synthetase?GS?gradually increased,while nitric acid Reductase?NR?activity increased first and then decreased;endophyte infection increased the nitrate nitrogen content and NR,GS,GDH activities of rice seedlings under Pb stress to a certain extent,but had no effect on GOGAT activity,indicating endogenous Bacterial infection can increase rice nitrogen metabolism and increase nitrogen accumulation.4.With the increase of Pb concentration,the chlorophyll fluorescence parameters F₀ and F_m of rice seedlings increased first and then decreased,but Fv/Fm decreased significantly,but there was no significant change in qN and qP;endophyte infection had no effect on Fm in rice seedlings under Pb stress.But it can increase qN,and endophyte infection can relieve the inhibitory effect of high concentration Pb on F₀.At a certain concentration,endophyte can protect the rice seedling PS?from Pb damage by enhancing the activity of PS?reaction center,increasing heat dissipation and promoting photosynthetic electron transfer.