Effect of exogenous 2,4-epibrassinolide on trace element absorption and chlorophyll fluorescence of Medicago sativa L. seedlings under NaCl stress Effect of La(NO3)3 on seedling growth and physiological characteristics of ryegrass under NaCl stress 2,4-epibrassinolide protection aginest root growth inhibition and oxidative damage of Medicago sativa L. seedling under NaCl stress