Antioxidant defense in the leaves of C3 and C4 plants under salinity stress

Abstract

The effect of salt stress (50, 100 and 150 mM of NaCl) on the activity of superoxide dismutase (SOD, EC. 1.15.1.1), ascorbate peroxidase (APX, EC. 1.11.1.11), glutathione reductase (GR, EC. 1.6.4.2) enzymes and also on the rate of lipid peroxidation in terms of thiobarbituric acid‐reactive substances (TBARS) content and photosynthetic capacity in two wheat (C3 plants) and two maize (C4 plants) varieties was studied. In the non‐salined control plants, the antioxidant enzymes activities were significantly higher for maize than for wheat. Adding salt to the nutrient solution increased the level of antioxidants in leaves of both maize and wheat. The first substantial response to salinity was found for SOD on the 2nd day, whereas changes occurred for APX on the 4th day and for GR on the 4th/5th day of salt treatment. Although SOD activity increased considerably more in wheat (C3), it never reached as high levels as in maize (C4) grown in the same treatment combinations. The total increase in APX activity was similar for wheat and maize, whereas GR activity was higher in leaves of maize. Lipid peroxidation analyses showed an increase in TBARS contents in both plants' species grown under salinity that corresponded to the damage that occurred in secondary oxidative stress. However, as a result of advanced antioxidant defense in maize, the TBARS quantities did not elevate to as high level as in wheat. Chlorophyll fluorescence measurements revealed a considerable decrease in the efficiency of PS II and electron‐transport chain (ETC). Assimilation rate of CO2 decreased in both plant groups; however, in C4 maize, we observed a much better capacity to preserve the photosynthetic apparatus against overproduction of ROS. Results suggest that efficient antioxidant defense plays an important role in maize, the C4 plant, resistance to environmental stresses like salinity or drought.

Comparison of ROS formation and antioxidant enzymes in Cleome gynandra (C4) and Cleome spinosa (C3) under drought stress

“…Similarly, Stepien and Klobus [14] also found that maize (C 4 ) had a higher constitutive level of SOD activity. In contrast to these results, Nayyar and Gupta [15] and Zhang and Kirkham [5] showed that the SOD activity levels varied insignificantly between maize/wheat, and sorghum/sunflower, respectively.…”

“…In these limited number of studies it was found that antioxidants play an important and efficient role, making maize (C 4 ) more resistant to environmental stresses than wheat (C 3 ) [14,15] and inherent lev- els of antioxidants in sorghum (C 4 ) were not consistently higher than in sunflower (C 3 ) under stress [5]. However, none of these studies were conducted on C 3 and C 4 species of the same genus; which would be useful to prevent involvement of other differences in plant metabolism and anatomy under stress conditions.…”

“…Moreover, in previous studies, differences in salt and drought tolerance between C 3 and C 4 species that belong to different genera were also reported [10,14,15]. For instance, the antioxidant defence mechanisms in the leaves of C 3 (wheat) and C 4 (maize) plants under salt and drought stress have been topics of different researchers [14,15].…”

“…For instance, the antioxidant defence mechanisms in the leaves of C 3 (wheat) and C 4 (maize) plants under salt and drought stress have been topics of different researchers [14,15]. However, we are not aware of any research on comparative ROS formation and antioxidant defence systems in the seedlings of C 3 and C 4 species of the same genus; this would be useful to prevent other differences in plant metabolism under stress conditions.…”

Effects of Salinity Stress on the Structure of Bundle Sheath and Mesophyll Chloroplasts in NAD-Malic Enzyme and PCK Type C4 Plants

“…C 4 plants are well suited to the growth in high intensity light, arid and warm environments (Black, 1973) and have been considered to have high resistance to salinity stress (Osmond et al, 1982;Stepien and Klobus, 2005). In previous studies conducted from a morphological viewpoint, bundle sheath cell (BSC) chloroplasts of C 4 plants showed higher tolerance to salinity stress than mesophyll cell (MC) chloroplasts, and ultrastructure of BSC chloroplasts remained nearly unaffected by salinity even if MC chloroplasts suffered catastrophic damage (Hasan et al, 2005(Hasan et al, , 2006Barhoumi et al, 2007;Omoto et al, 2009).…”