Alleviation Of Exogenous Citric Acid And Glutamic Acid On Italian Ryegrass Under Aluminum Stress

Italian ryegrass(Lolium multiflorum Lam.)is a high-quality forage grass distributed in temperate and subtropical regions,especially in the agricultural areas south of the Yangtze River Basin in my country.However,it is often subjected to a certain amount of adversity stress in relatively acidic soils with relatively high aluminum ion content.In this study,Italian ryegrass was used as a material,and the potting method was used to investigate the effects of exogenous citric acid and glutamic acid on organ establishment and related physiological indexes of Italian ryegrass under aluminum stress.The main findings are as follows:1.Aluminum ions had toxic effects on the growth and physiology of leaves and roots of Italian ryegrass.Compared with the control group,aluminum stress extremely significantly(P<0.01)inhibited the plant height and root elongation,and the accumulation of above-ground and underground biomass of Italian ryegrass;Studies on chlorophyll in leaves found that aluminum stress significantly(P<0.05)reduced the chlorophyll content,and significantly(P<0.05)reduced the transient curve of chlorophyll a fluorescence OJIP,and destroyed the chlorophyll fast and slow fluorescence parameters;Aluminum stress significantly(P<0.05)increased the concentration of aluminum ions,SOD and CAT activity,soluble sugar and soluble protein content,and also increased the relative conductivity and MDA content in leaves and roots,but significantly(P<0.05)inhibited the secretion of citric acid in leaves and roots;In addition,aluminum stress also reduced the content of free amino acids in leaves and roots to a certain extent.2.The addition of exogenous citric acid could alleviate the aluminum toxicity in leaves and roots of Italian ryegrass.Its main performance was:Compared with the aluminum treatment group,the addition of citric acid under aluminum stress could significantly(P<0.05)increase the plant height,root length,aboveground and underground biomass of Italian ryegrass;Adding citric acid under aluminum stress increased chlorophyll content,and also improved the transient curve of chlorophyll a fluorescence OJIP.The specific performance was:Citric acid treatment increased the Fo,Fj,Fi,Fm,and F300?s values of Italian ryegrass,and also significantly(P<0.05)improved quantum yield and efficiency,reduced specific energy flux,thereby increasing the PIABS and PItotai values to a certain extent.At the same time,analysis of chlorophyll slow fluorescence parameters showed that Fv/Fm,Y(?),qP,qL,and ETR values of citric acid treatment under aluminum stress were significantly(P<0.05)higher than those of aluminum stress treatment,and Y(NPQ),Y(NO),NPQ and qN values were significantly lower(P<0.05)than those in the aluminum stress treatment group;After the addition of citric acid,the content of soluble sugar and soluble protein increased and the content of citric acid increased significantly(P<0.05),while the content of aluminum ions decreased significantly(P<0.05)in leaves and roots under aluminum stress;1.6 mmol·L-1 citric acid treatment could also significantly(P<0.05)reduce the relative electrical conductivity and MDA content in leaves and roots under aluminum stress;However,citric acid treatment increased the activities of SOD and CAT,but also decreased the activities of POD in leaves and roots under aluminum stress;In addition,citric acid treatment also increased the content of free amino acids in leaves and roots under aluminum stress.3.The addition of exogenous glutamic acid could alleviate aluminum toxicity in leaves and roots of Italian ryegrass.Its main performance was:The addition of exogenous glutamic acid under aluminum stress could significantly(P<0.05)promote the plant height and root length elongation and the accumulation of above-ground and underground biomass of Italian ryegrass;Addition of glutamic acid under aluminum stress significantly(P<0.05)increased chlorophyll content;Studies on chlorophyll fast fluorescence found that adding glutamate under aluminum stress improved the chlorophyll a fluorescence OJIP transient curve,and also increased Fj,Fi,Fm and F300?s values,while improved the quantum yield and efficiency,and reduced the specific energy flux,thereby significantly(P<0.05)increased the PIABS and PItotal values;Analysis of chlorophyll slow fluorescence parameters found that the values of Fv/Fm,Y(?),qP,qL,and ETR in the glutamate-treated group were higher than those in the aluminum-stressed group,and Y(NPQ),Y(NO),NPQ and qN values were all lower than those in the aluminum stress treatment group;The addition of glutamic acid also increased the soluble sugar and soluble protein content,and significantly(P<0.05)increased the citric acid,and decreased the relative conductivity and MDA content,and significantly(P<0.05)reduced the aluminum ion content in leaves and roots under aluminum stress;Exogenous glutamate treatment significantly(P<0.05)increased SOD and CAT activities,but reduced POD activities in leaves and roots under aluminum stress;However,the effects of exogenous glutamic acid treatment on the content of free amino acids in leaves and roots under aluminum stress were different.When glutamic acid was added under aluminum stress,the contents of glutamic acid,aspartic acid,serine,threonine,alanine,proline,valine and leucine in leaves decreased significantly(P<0.05).But the content of glutamic acid,threonine,alanine,proline and leucine in the root system were all increasedIn summary,Aluminum stress had toxic effects on the growth and physiology of Italian ryegrass.The addition of a certain concentration of citric acid and glutamic acid could effectively alleviate the toxic effect of aluminum stress on leaves and roots of Italian ryegrass.and the changes of various indicators in leaves and roots were basically consistent.It provided a theoretical reference for improving the aluminum tolerance of Italian ryegrass by using organic acids and amino acids.