Relative importance of Na⁺ and Cl^– in NaCl‐induced antioxidant systems in roots of rice seedlings

Abstract

The present study examined the response of antioxidant systems to NaCl stress and the relative importance of Na 1 and Clin NaCl-induced antioxidant systems in roots of rice seedlings. NaCl treatment caused an increase in the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in roots of rice seedlings, but had no effect on the activities of superoxide dismutase (SOD) and catalase (CAT). There were detectable differences in APX and GR isoenzymes between control and NaCl-treated roots. Levels of activity for SOD and CAT isoenzymes did not change in NaCl-stressed roots compared with the control roots. NaCl treatment produced an increase in H 2 O 2 , ascorbate (AsA), dehydro-ascorbate (DHA), reduced glutathione (GSH), and oxidized glutathione (GSSG) levels. Treatment with 50 mM Na-gluconate (whose anion is not permeable to membrane) led to a similar Na 1 level in roots to that with 100 mM NaCl. It was found that treatment with 50 mM Na-gluconate affected H 2 O 2 , AsA, and DHA levels, APX and GR activities, OsAPX and OsGR mRNA induction in the same way as 100 mM NaCl. These observed changes seem to be mediated by Na 1 toxicity and not by Cltoxicity. On the other hand, it was found that NaCl, but not Na-gluconate and NaNO 3 , caused an increase in GSH and GSSG levels, indicating that Cl -, rather than Na 1 , is responsible for the NaCl-increased GSH and GSSG levels in roots of rice seedlings.

A hydroponic rice seedling culture model system for investigating proteome of salt stress in rice leaf

“…Enhanced responses of APX under salt stress in this study are in a good agreement with previous findings [20,21]. Different from an enhanced response of APX under salt stress, the activity of CAT was (i) found to be either unaltered or even reduced in response to salt stress [21][22][23], and (ii) accelerated in a salt-tolerant rice cv. with increasing salt stress, and correlated with a lower level of H 2 O 2 content and lipid peroxidation [78].…”

“…In contrast, the cross-reacting CAT protein spot was down-regulated by salt stress. These results are in line with the previously determined enzyme activities of APX and CAT in response to salt stress [21][22][23]. Interestingly, we discussed in Section 3.2 about a high-molecular-weight putative CAT protein whose amount increased under salt stress.…”

“…It was also found that salt stress preferentially increased hydrogen peroxide (H 2 O 2 ) content as well as the activities of APX [21]. Different from an enhanced response of APX under salt stress, the activity of another essential H 2 O 2 scavenging enzyme, catalase (CAT), seemed to be either unaltered or even reduced in response to salt stress [21][22][23].…”

Triacontanol-induced Regulation in the Key Osmoprotectants and Oxidative Defense System of Sunflower Plants at Various Growth Stages under Salt Stress

“…Similarly, the decreased activity of the SOD under saline stress might be due to the increased accumulation of the H 2 O 2 and inhibition of activity of SOD by sodium ion toxicity (Dionisio-Sese and Tobita, 1998). In similar to our findings, a marked decrease in POD activity was observed in wheat (Gadalla, 2009) while the nonsignificant behavior of the CAT was recorded in rice (Tsai et al, 2004). Reduced activity of SOD has also been reported in pea plants under salinity (Hernandez et al, 1995).…”

Antioxydant response to biotic and abiotic inducers for the resistance against fusarium wilt disease in eggplant (solanum melongena l.)

“…The H 2 O 2 content was measured colorimetrically after reaction with TiCl 4 as described by TSAI et al (2004) with slight modifications. The reaction mixture consisted of 1.8 mL of 50 mM phosphate buffer (pH 7.0), 0.2 mL of leaf extract supernatant and 1 mL reagent…”