Physiological Regulation Of Potassium,EBR And MeJA On Reaumuria Trigyna Maxim.in Response To Salt And Drought Stress

Reaumuria trigyna Maxim.belongs to the Reaumuria Linn in the family Tamarieaceae.It is a small perennial halo shrub distributed in the East Alxa-West Ordos region,which is one of the important constructive plants in the desert area.It is highly adaptable to abiotic stress such as salt,drought and UV-B.Potassium is important metal ions in plants,maintaining the dynamic balance of potassium ions is essential for plants to respond to abiotic stress.2,4-epibrassinolide（EBR）is a polyhydroxylated steroid plant hormone that can induce plants to respond to abiotic stress,and respond to a variety of stresses to improve plant resistance.Methyl jasmonate（MeJA）is a very important hormone in plants that can respond to a variety of abiotic stresses including salt,drought,and low temperature.In this study,R.trigyna seedlings were used as the experimental material,and were applied with different concentrations of K⁺,1μM EBR and 1μM MeJA under salt（NaCl）and drought（PEG-6000）.Our detected the growth index,membrane damage degree,and antioxidant enzyme activity R.trigyna seedlings under different treatments,and detected changes in osmotic adjustment and ion balance,and synthetically analyzed the physiological regulation of K⁺,EBR and MeJA on R.trigyna under salt and drought conditions.The main results are as follows:1.We found that under the stress of 400 mM NaCl and 10%PEG,the plant height,root length,photosynthetic pigment and other growth indicators of R.trigyna seedlings were reduced,and a large amount of reactive oxygen species,the content of proline and the activity of antioxidant enzymes were increased.The growth of R.trigyna seedlings was inhibited.2.Low potassium could further aggravate the growth inhibitory effect of salt or drought stress on R.trigyna seedlings,reduce the accumulation of photosynthetic pigments and the content of proline in the leaves,and increase the activity of POD in the leaves,the level of ROS accumulation,and the Na⁺/K⁺ratio and the Ca²⁺content of leaves under stress.And low potassium aggravated the oxidative damage caused by stress to the plant,and the osmotic balance and ion homeostasis were further unbalanced.Thereby the stress resistance of R.trigyna seedlings was reduced.The result of high potassium treatment is contrary to the result of low potassium treatment.The result of high potassium treatment was that under the stress the inhibitory effect on the growth of R.trigyna was relieved,at the same time the activity of SOD and CAT and the contents of proline and soluble sugar in the leaves were increase,and the level of ROS accumulation was reduce.Under stress conditions,the Na⁺/K⁺ratio in the leaves of seedlings was reduced,the level of oxidative damage caused by stress to the plant was reduced,and a new osmotic balance and ion homeostasis were formed in plant.Thereby the stress resistance of R.trigyna seedlings was enhanced.3.Treatment of exogenous EBR could increase plant height,root length,relative water content,photosynthetic pigment and other growth indicators,and alleviate the adverse effects of stress by enhancing photosynthetic capacity and improving water conditions.Exogenous EBR treatment could increase the POD enzyme activity and proline accumulation in the leaves of R.trigyna under stress,reduce ROS production,and alleviate the physiological damage effect of salt and drought stress on R.trigyna through antioxidant regulation and osmotic adjustment.EBR also regulated the absorption,transport and distribution of inorganic ions,promoted the expression of potassium ion transport genes,reduced the ratio of Na⁺/K⁺,increased the content of Ca²⁺,and formd a new ion steady state,thereby enhancing the stress resistance of R.trigyna seedlings.In addition,EBR might regulate osmotic systems,antioxidant regulation and ion balance systems through the ABA signaling pathway to improve plant resistance to stress.4.Exogenous MeJA treatment could reduce the activity of antioxidant enzymes（SOD,POD,CAT）in leaves,further increase the content of active oxygen,MDA,relative conductivity,and Na⁺/K⁺ratio,and decrease the content of photosynthetic pigments.It was speculated that MeJA might regulate antioxidant enzymes system,osmotic homeostasis,and ion balance to enhance the sensitivity of R.trigyna to salt and drought.Among them,under salt stress,MeJA might regulate the antioxidant system,osmotic homeostasis,and ion balance system through the ABA-mediated senescence mechanism to reduce the tolerance of plants for salt.