The oxidative stress caused by salinity in two barley cultivars is mitigated by elevated CO₂

Abstract

Changes in antioxidant metabolism because of the effect of salinity stress (0, 80, 160 or 240 mM NaCl) on protective enzyme activities under ambient (350 micromol mol(-1)) and elevated (700 micromol mol(-1)) CO(2) concentrations were investigated in two barley cultivars (Hordeum vulgare L., cvs Alpha and Iranis). Electrolyte leakage, peroxidation, antioxidant enzyme activities [superoxide dismutase (SOD), EC 1.15.1.1; ascorbate peroxidase (APX), EC 1.11.1.11; catalase (CAT), EC 1.11.1.6; dehydroascorbate reductase (DHAR), EC 1.8.5.1; monodehydroascorbate reductase (MDHAR), EC 1.6.5.4; glutathione reductase (GR), EC 1.6.4.2] and their isoenzymatic profiles were determined. Under salinity and ambient CO(2), upregulation of antioxidant enzymes such as SOD, APX, CAT, DHAR and GR occurred. However, this upregulation was not enough to counteract all ROS formation as both ion leakage and lipid peroxidation came into play. The higher constitutive SOD and CAT activities together with a higher contribution of Cu,Zn-SOD 1 detected in Iranis might possibly contribute and make this cultivar more salt-tolerant than Alpha. Elevated CO(2) alone had no effect on the constitutive levels of antioxidant enzymes in Iranis, whereas in Alpha it induced an increase in SOD, CAT and MDHAR together with a decrease of DHAR and GR. Under combined conditions of elevated CO(2) and salinity the oxidative damage recorded was lower, above all in Alpha, together with a lower upregulation of the antioxidant system. So it can be concluded that elevated CO(2) mitigates the oxidative stress caused by salinity, involving lower ROS generation and a better maintenance of redox homeostasis as a consequence of higher assimilation rates and lower photorespiration, being the response dependent on the cultivar analysed.

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

“…This was particularly evident for Ala, Val, and Ser as one group and, to a lesser extent, His, Phe, and Tyr as another. The amounts of Gly were notably lower than expected, which might be explained by the generally lower levels of photorespiration in Poaceae (Engel et al, 2007;Perez-Lopez et al, 2009). …”

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

“…When ferredoxin is overreduced during photosynthetic electron transfer, electrons that have a high-energy state are trans-contribute in maintaining the integrity of cell structures and the proper functions of various metabolic pathways [4]. The degree to which the activities of antioxidant enzymes and the amount of antioxidants are elevated under drought stress shows a remarkable variation among plant species [5,6] and even between two cultivars of the same species [7,8]. In recent years, many researchers have established that the induction of the cellular antioxidant machinery is important for tolerance to drought stress [9].…”

The competition between winter rape (C3) and maize (C4) plants in response to elevated carbon dioxide and temperature, and drought stress

“…In maize plants phenolic compound accumulation and DPPH-free radical scavenging capacity were more expressed than in winter rape plants . The degree to which the activities of antioxidants enzymes and the amount of antioxidants are elevated under stressful conditions is extremely variable among several plant species (Nayyar, Gupta, 2006) and even between cultivars of the same species (Pérez-López et al, 2009;Uzilday et al, 2011). An increase in phenolic compounds and antioxidant activity was detected in winter rape when grown in mixture.…”

“…Under stressful environmnetal conditions the activity of antioxidant enzymes and the amount of antioxidants are elevated in plants and are speciesspecific (Nayyar, Gupta, 2006) or even cultivar-specific (Pérez-López et al, 2009;Uzilday et al, 2011).…”