Exogenous EBR mediated the plant growth and absorption and accumulation of Cu, Fe and Zn in tomato seedlings under Cu stress Effect of exogenous 2,4-epibrassinolide on trace element absorption and chlorophyll fluorescence of Medicago sativa L. seedlings under NaCl stress 2,4-epibrassinolide protection aginest root growth inhibition and oxidative damage of Medicago sativa L. seedling under NaCl stress Effects of brassinolide and auxin on growth, carbon and nitrogen metabolism and tobacco quality of flue-cured tobacco leaves after topping