Effects Of Exogenous Glycinebetaine On Aluminum Tolerance Of Rice And Maize

Acid soil is mainly distributed in the south of China,accounting for about 22%of the country's land area.Aluminum toxicity is an important limiting factor for plant growth and development in acid soil.Aluminum toxicity not only damages the growth and development of plant roots,but also influences the absorption of water and nutrients.Moreover,it will destroy the biomembrane system,produce excessive ROS,damage organelles and plant function.As a compatible substance,glycinebetaine has the functions of osmotic regulation,scavenging reactive oxygen species,maintaining the stability of biofilm,protecting the photosynthetic mechanism and maintaining the stability of macromolecular protein complex.It also plays an important role in many abiotic stresses such as high temperature stress,low temperature stress,salt stress,drought stress and heavy metals stress.However,not all plants can synthesize glycinebetaine.For example,glycinebetaine can not be synthesized in Arabidopsis,tomato,potato and rice.Maize only can synthesize a few glycinebetaine.In addition,there are few studies on the roles of glycinebetaine under aluminum stress.In order to verify the regulatory role of glycinebetaine under aluminum stress,this experiment adopted the method of exogenous application of glycinebetaine to carry out an experimental study on rice and corn under aluminum stress.The experimental results are as follows:?1?Under aluminum stress,the aboveground growth of maize and rice was inhibited,and the exogenous application of glycinebetaine reduced the degree of inhibition,so that the biomass of the upper part of rice and maize was increased.However,inhibition of root elongation increased after exogenous application of glycinebetaine.In addition,exogenous application of glycinebetaine had a positive effect on the growth of tissue cells in rice stem.?2?Under aluminum stress,chlorophyll content,?PSI,ETR?I?,?PSII and ETR?II?is reduced,the active of photosystem is restrained.Exogenous application of glycinebetaine can increase the content of chlorophyll and maintain the photochemical efficiency of photosystem I and photosystem II at a normal level.Photoelectron transfer rate is also maintained at a high level and the utilization rate of light energy is high.The damage of aluminum stress to the photosystem is alleviated.?3?Under aluminum stress,the content of MDA and O₂.^-in rice and maize increased,and the plants were subjected to severe oxidative stress.The oxidative stress was alleviated after exogenous application of glycinebetaine.In addition,the activity of antioxidant enzyme was improved to different degrees and the scavenging function of reactive oxygen species was enhanced.The content of soluble substance proline and soluble protein after exogenous glycinebetaine was higher than that under aluminum treatment,which enhanced the aluminum tolerance of rice and corn.?4?Under the aluminum stress,the aluminum accumulation in rice and corn increased.In rice,the aluminum accumulation in the underground part increased,and in the aboveground part decreased after exogenous application of glycinebetaine.Nevertheless,the application of glycinebetaine to corn had no effect on the accumulation of aluminum.Furthermore,exogenous application of glycinebetaine increased the ratio of aluminum content in rice root cell wall.Exogenous application of glycinebetaine can reduce the decrease of calcium ion content caused by aluminum stress and maintain the normal ion level in plants.?5?Exogenous application of glycinebetaine under aluminum stress increased the content of galacturonic acid in the root cell wall,increased the binding site of aluminum ions,and resulted in a large accumulation of aluminum ions in the root.At the same time,the expression of gene encoding aluminum transporter protein on plasma membrane and vacuole membrane was increased,and more aluminum ions accumulated in vacuole,which reduced the content of aluminum transported to the shoot.