The Alleviative Effects of Salicylic Acid on the Activities of Catalase and Superoxide Dismutase in Malting Barley (Hordeum uhulgare L.) Seedling Leaves Stressed by Heavy Metals

As toxic divalent heavy metal ions, Zn 2+ , Cu 2+ , Mn 2+ , Cd 2+ , Hg 2+ , and Pb 2+ exert certain negative effects on plant growth and development, which has been paid huge amount of attention to in the management of heavy metal pollution. As a novel kind of endogenous plant hormone, salicylic acid (SA) is considered to exert beneficial physiological effects on plants. In this paper, the activities of catalase (CAT) and superoxide dismutase (SOD) in seedling leaves of a malting barley variety (called Ganpi No.4) cultured under hydroponic cultivation was measured under different treatments of Zn 2+ , Cu 2+ , Mn 2+ , Cd 2+ , Hg 2+ , and Pb 2+ and under different treatments of SA alleviation, respectively, and such values were then compared and analyzed. The results showed that all treatments of different ions and the activities of CAT and SOD and all SA‐alleviated treatments and the activities of CAT and SOD exhibited nonlinear relationships. Zn 2+ , Cu 2+ , Mn 2+ exerted less severe stresses on the activities of CAT and SOD at lower concentrations, and led to significantly inhibitive effects on the activities of CAT and SOD at higher concentrations. And Cd 2+ , Hg 2+ , and Pb 2+ exerted significantly repressing effects on the activities of CAT and SOD. As for SA's alleviative effects, such effects were salient for most concentrations of Mn 2+ , Zn 2+ , and Cu 2+ treatments and lower concentrations of Cd 2+ , Hg 2+ , and Pb 2+ treatments, while were not significant for higher concentrations of Cd 2+ , Hg 2+ , and Pb 2+ treatments. These data provided theoretical references for studies on physiological mechanism of cereal crops' resistance or tolerance to heavy metal stress as biomarkers.