Alleviation Of Exogenous Salicylic Acid And NO On Ryegrass Under A1 Stress

Ryegrass is a grassy forage with a large area planted in southern China.It has many advantages such as many tillers,developed roots,long green period,high grass yield and high nutritional value.However,the soil in the south of China is acidic.When the soil pH is below 5,these aluminum elements are dissolved into biotoxic Al3+,which is toxic to plants.It can be seen that aluminum stress is an important factor restricting the production of ryegrass in acidic soils in China.Therefore,discovering ryegrass with better aluminum resistance and improving the aluminum resistance of ryegrass are important issues to be solved urgently.In this study,the aluminum tolerance of 21 different varieties of ryegrass was firstly evaluated.The effects of exogenous salicylic acid and nitric oxide on the growth,physiology,photosynthesis and Al-Cl enrichment of ryegrass under Al stress were investigated on the basis of screening of Al-tolerant ryegrass and Al-sensitive ryegrass.The main findings are as follows:1.Aluminum stress inhibited the root and plant growth of ryegrass,which mainly showed that aluminum stress reduced the plant height and root length of ryegrass,and reduced the accumulation of aboveground biomass and underground biomass.At the same time,aluminum stress reduced the chlorophyll content of ryegrass and increased the content of MDA.In order to eliminate ROS in ryegrass,SOD activity was increased and soluble protein content was decreased.2.The responses of different varieties of ryegrass to different growth and physiological indices were different under Al stress.In this study,plant height,root length,aboveground biomass,underground biomass,chlorophyll content,MDA content,SOD activity,soluble sugar content and soluble protein were used as evaluation criteria,and membership function was used to evaluate the A1 tolerance of 21 ryegrass species.The evaluation results show that Tetragold has a high aluminum tolerance,while Nagahahikari belongs to aluminum stress sensitive materials.3.Aluminum stress reduced the transient curve of chlorophyll fluorescence OJIP of ryegrass,increased Fo,decreased Fm and ion yield and efficiency and increased specific energy flux.It damaged the photosynthetic system and reduced its performance indicators PIABS and PItotal,which affected the photosynthetic performance.4.The addition of SA(0.6 mmol/L)to ryegrass under aluminum stress could significantly increase the chlorophyll content,protect the photosynthetic components and improve the parameters of chlorophyll a fluorescence performance index.It also reduced the concentration of aluminum and MDA content in organisms,but increased the activity of SOD and POD,and increased the content of soluble sugar.5.Adding SA under aluminum stress increased the soluble protein content of ryegrass Nagahahikari,but decreased the CAT activity.However,the addition of SA under aluminum stress reduced the high soluble protein content of ryegrass,but increased the CAT activity.6.There are differences in the alleviation effects of SA on two kinds of ryegrass under aluminum stress.The alleviation effect of sensitive ryegrass Nagahahikari is more obvious than that of aluminum-resistant ryegrass Tetragold.7.Exogenous NO treatment could improve the chlorophyll content,chlorophyll fluorescence performance parameters,soluble sugar and soluble protein content of ryegrass under aluminum stress.By increasing the activity of antioxidant enzymes(SOD,POD and CAT)to remove ROS and reducing the concentration of Al in ryegrass,the growth and biomass accumulation of ryegrass were promoted,so as to improve the adaptability of ryegrass to Al stress.8.There is a difference between NO and the mitigation effects of two kinds of ryegrass under aluminum stress.The alleviation effect of sensitive ryegrass Nagahahikari is more obvious than that of aluminum-resistant ryegrass Tetragold.In summary,21 varieties of ryegrass were evaluated comprehensively for their Al-tolerance,and Al-tolerant and Al-sensitive varieties were screened out.In addition,we found that adding exogenous salicylic acid and NO could improve the aluminum tolerance of ryegrass,which provided an important basis for future research on aluminum tolerance of ryegrass.