The ecotoxicological and interactive effects of chromium and aluminum on growth, oxidative damage and antioxidant enzymes on two barley genotypes differing in Al tolerance

The effects of single or combined stress of aluminum (Al) and chromium (Cr) on plant growth, root dehydrogenase, oxidative stress and antioxidative enzymes were studied using two barley genotypes differing in Al tolerance in a hydroponic experiment. Al or Cr stress decreased plant growth, lowered root dehydrogenase activity and caused oxidative damage, as characterized by increased MDA and H2O2 contents. Under Al or Cr stress, the activities of antioxidative enzymes, including superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) and catalase (CAT), were dramatically increased in plant tissues. Gebeina, an Al-tolerant genotype, had less oxidative damage than Shang 70-119, an Al-sensitive genotype. The extent of oxidative damage induced by Cr varied with the pH of the culture solution, with lower pH values (4.0) being more severe than higher pH values (6.5). The combination of Cr and Al caused a further decrease in plant growth, a decrease in root dehydrogenase activity and an increase in MDA and H2O2 contents as well as the activities of antioxidative enzymes. There was also a marked difference between the two barley genotypes in the extent of increased antioxidative enzyme activity under the Cr and Al stresses.

Research highlights▶ Under Al or Cr stress, the activities of antioxidative enzymes, including superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), gluthione reductase (GR) and catalase (CAT) were dramatically increased in plant tissues. ▶ Al-tolerant genotype had relatively less oxidative damage than Al-sensitive genotype. ▶ The extent of oxidative damage induced by Cr varied with pH in culture solution, with lower pH (4.0) being more severe than higher pH (6.5). ▶ Combination of Cr and Al caused further decrease in plant growth, root dehydrogenase activity and increase in MDA and H2O2 contents as well as activities of antioxidative enzymes. ▶ There was a marked difference between barley genotypes in the increased extent of the antioxidative enzyme activity under the Cr and Al stresses.