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Seedlings growth and antioxidative enzymes activities in leaves under heavy metal stress differ between two desert plants: a perennial (Peganum harmala) and an annual (Halogeton glomeratus) grass

Lu, Yan, Li, Xinrong, He, Mingzhu, Zhao, Xin, Liu, Yubing, Cui, Yan, Pan, Yanxia, Tan, Huijuan
Acta physiologiae plantarum 2010 v.32 no.3 pp. 583-590
Halogeton glomeratus, Peganum harmala, antioxidant activity, ascorbate peroxidase, catalase, grasses, heavy metals, hydrogen peroxide, leaves, metal tolerance, oxidative stress, seedling growth, seedlings, superoxide dismutase, toxicity testing, xerophytes
The present study showed the toxicity caused by heavy metal and its detoxification responses in two desert plants: perennial Peganum harmala and annual Halogeton glomeratus. In pot experiments, 1-month-old seedlings were grown under control and three levels of combined heavy metal stress. Seedling growth as well as heavy metal accumulation, antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] activities and the contents of malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) in leaves was examined after 2 months of heavy metal exposure. Compared with H. glomeratus, growth of P. harmala was more severely inhibited. In leaves, the heavy metal accumulation pattern in both the plants was dose-dependent, being more in H. glomeratus. H. glomeratus exhibited a typical antioxidative defense mechanism, as evidenced by the elevated activities of all the three enzymes tested. P. harmala exhibited a different enzyme response pattern, with a significant reduction in CAT activity, and elevated SOD and APX activities, but significantly elevated APX activity was only at the lowest heavy metal concentration. MDA and H₂O₂ contents were significantly enhanced in leaves of heavy metal-treated P. harmala, but in H. glomeratus were elevated only at the highest heavy metal treatment. These results indicated that H. glomeratus had a greater capacity than P. harmala to adapt to oxidative stress caused by heavy metal stress, and antioxidative defense in H. glomeratus might play an important role in heavy metal tolerance.