7Dhindsa R S, Plumb-Dhindsa P, Thorpe T A. Leaf senescence: Correlated with increased levels of membrane permeability and lipid peroxidation, and decreased levels of superoxide dismutase and catalase[J]. Journal of Experimental Botany, 1982,32( 1 ):93-101.
9Ayuso M, Hermandez Z T, Garcia C. A comparative study of the effect on barley growth of humic substances extracted from municipal wastes and from traditional or- ganic materials[J]. J. Sci. Food Agric., 1996, 72(4): 493 500.
10Moll R H, Kamprath E J, Jackson W A. Analysis and interpretation of factor which contribute to efficiency of nitrogen utilization[J]. Agron J, 1982, 74:562 - 564.