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Assessment of the effects of zinc on the growth and antioxidant enzymes in Scenedesmus ellipsoideus Chodat

Hediye Elif Kiliç, Tunca Hatice, Ongun Sevindik Tuğba, Doğru Ali

Oceanological and Hydrobiological Studies

2019

Vol. 48, No. 3

270--278

This study explores the activity of total superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR), biomass accumulation and chlorophyll a content in Scenedesmus ellipsoideus Chodat grown under conditions of varying zinc (Zn) concentrations. In addition, the activity of different SOD isozymes (MnSOD, FeSOD and CuZnSOD) was measured separately to determine the intracellular extent of oxidative stress resulting from Zn toxicity. We found that the activity of FeSOD and MnSOD was induced by lower Zn concentration (2 μg ml−1 and 4 μg ml−1, respectively), whereas CuZnSOD activity was not affected, which indicates that chloroplasts are the first location in S. ellipsoideus cells where superoxide accumulation is accelerated by Zn toxicity. The activity of total SOD and APX was significantly increased by moderate Zn concentrations, probably due to some oxidative stress caused by Zn toxicity. The higher level of Zn application, however, led not only to the inhibition of total SOD and APX activity, but also to the reduction of biomass accumulation and chlorophyll a content. As a result, it can be concluded that the accumulation of superoxide radicals and H2O2 in S. ellipsoideus cells induced by Zn toxicity may be responsible for the reduced growth rate and the impairment of photosynthetic pigments.

The effect of multiple heavy metals on ascorbate, glutathione and related enzymes in two mangrove plant seedlings (Kandelia candel and Bruguiera gymnorrhiza)

Huang G-Y., Wang Y-S., Sun C-C., Dong J-D., Sun Z-X.

Oceanological and Hydrobiological Studies

2010

Vol. 39, No.1

11-25

In this study, the effect of multiple heavy metal stress on ascorbate (AsA), glutathione (GSH) and related enzymes was investigated in the leaves, stems and roots of Kandelia candel and Bruguiera gymnorrhiza. Mangrove seedlings were treated with five different concentrations of a heavy metal mixture (Cd^2+, Pb^2+ and Hg^2+). Antioxidants in both the species were analyzed after one month. AsA, GSH, ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) exhibited a similar trend with initial increase and subsequent decrease in response to heavy metal stress. At the highest metal concentration, a significant decrease of AsA and GR was observed in K. candel and B. gymnorrhiza. Glutathione peroxidase (GPX, EC 1.11.1.9) in the leaves, stems and roots of K. candel reached their respective maximal values at the highest metal concentration, whereas GPX activity in roots and stems of B. gymnorrhiza was similar to the controls at higher metal concentrations. Our results demonstrate that AsA, GSH, APX, GR and GPX in K. candel may play more important roles in defending against reactive oxygen species (ROS) than those in B. gymnorrhiza.