Effects of exogenous melatonin on the growth and physiological characteristics of Rhus chinensis seedlings under salt stress
Our experiment utilized 3-month-old Rhus chinensis seedlings as materials.Exogenous melatonin was ap-plied via foliar spraying,with concentrations of 0 μmol/L,50 μmol/L,100 μmol/L,and 150 μmol/L.The seedlings were pretreated with the melatonin solutions before exposure to salt stress induced by a 150 mmol/L NaCl solution.The study investigated the effects of exogenous melatonin pretreatment on the growth,osmotic regulation substance content,antioxidant enzyme activity,and the expression levels of related genes in R.chinensis seedlings under salt stress condi-tions.The results indicated that:salt stress significantly inhibited the growth of R.chinensis seedlings,with a notable de-crease in plant height and relative water content;under various concentrations of melatonin pre-treatment,salt-induced symptoms were alleviated,and leaf relative water content and plant height showed a significant increase;under salt stress,the leaves accumulated soluble sugars,soluble proteins,and proline,while pre-treatment with 100 μmol/L mela-tonin could significantly promote the increase in soluble sugar and proline content;salt stress significantly increased the contents of malondialdehyde(MDA)and hydrogen peroxide(H202),while melatonin pretreatment significantly induced the activity enhancement of catalase(CAT),superoxide dismutase(SOD),and ascorbate peroxidase(APX),and re-duced the contents of MDA and H2O2;exogenous melatonin pre-treatment significantly enhanced the relative expression levels of salt stress-responsive genes RcRBOHF,RcABF3,RcRD20,and RcRD22 in the leaves of salt-stressed R.chi-nensis seedlings.This study reveals that melatonin pretreatment enhances the salt resistance of R.chinensis,providing a theoretical basis for utilizing melatonin to improve its salt tolerance,and providing useful references for breeding excellent salt tolerant varieties and the development and utilization of saline soil.
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