Alleviation Of Endophyte EF0801 From S.salsa To The Damage Of Rice Seedlings Under PEG Stress

In recent years,the effects of global warming or atmospheric circulation on precipitation are all contributed to the deterioration of the global drought situation,the utilization of land resource is getting lower and lower,which influence on the crop production and economic development,and even the social level.Rice as the main food crop in China,it is very important to study the resistance of rice under water stress,and it is an important foreshadowing to improve the grain yield and safety of our country.Endophyte can improve resistance of plants to stress.Using rice seedlings as the experimental material,they were divided into two groups(E+:endophyte-infected seedlings,E-: endophyte-uninfected seedlings).Each group was randomly assigned to five polyethylene glycol 6000(PEG)treatments(concentrations of 0,5,10,15 and20% in Hoagland's solution).Measuring the change of morphological characters(plant height,root length,aboveground and belowground dry weight),relative water content,photosynthetic indexes(chlorophyll a,b content,photosynthetic and fluorescence parameters),antioxidant system(antioxidase activity and antioxidant content),reactive oxygen species,proline and mineral elements content of rice seedlings,to assess the mechanism of endophyte on physiological responses of rice seedlings under PEG stress.Research results shows:1.PEG stress inhibited the growth of the height and root length,accumulation of dry weight,and decreased the relative water content of rice seedlings.The infection of endophyte alleviated the inhibition of PEG stress on shoot height and dry weight.The relative water content of E+ is higher than that of E-,and the greater water stress,the more obvious difference.2.PEG stress decreased chlorophyll content,net photosynthetic rate,stomatal conductance,and the fluorescence parameters(Fv/Fm,Fv/Fo),and inhibited the photosynthesis.After the infection of endophyte,the above parameters of E+ are higher than those of E-.It can be seen that endophyte reduce the damage to photosynthetic organs and improve the photosynthesis.3.PEG stress increased the content of hydrogen peroxide and superoxide anion,electric conductivity and MDA and proline content,caused membrane peroxidation.The infection of endophyte suppressed the production of reactive oxygen on a certain degree,reduced the damage of membrane due to PEG stress.4.PEG stress reduced the activity of ascorbic acid peroxidase and the content of antioxidant.The infection of endophyte promoted the ASA-GSH cycle,improved the content of TGSH and GSH,reduced the damage of antioxidant system under PEG stress and improved the resistance.5.PEG stress inhibited the accumulation of mineral elements,such as P,K,Fe in leaves and Ca,Mg,P,Fe in roots.The content of K?Mg and P of E+ is higher than those of E-in leaves androots.The infection of endophyte promoted the physiological metabolism of rice on a certain extent through improving the absorbtion of mineral elements.