Sphaerophysa kotschyana, an endemic species from Central Anatolia: antioxidant system responses under salt stress

Sphaerophysa kotschyana is a Turkish endemic and endangered plant that grows near Salt Lake, in Konya, Turkey. However, little is known about the ability of this plant to generate/remove reactive oxygen species (ROS) or its adaptive biochemical responses to saline environments. After exposure of S. kotschyana to 0, 150, and 300 mM NaCl for 7 and 14 days, we investigated (1) the activities and isozyme compositions of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), and glutathione reductase (GR); (2) the oxidative stress parameters NADPH oxidase (NOX) activity, lipid peroxidation (MDA), total ascorbate (tAsA) content, and total glutathione content (tGlut); and (3) ROS levels for superoxide anion radical (O (2) (center dot-) ), hydrogen peroxide (H2O2), hydroxyl radicals (OH center dot), and histochemical staining of O (2) (center dot-) and H2O2. H2O2 content increased after 14 days of salt stress, which was consistent with the results from histochemical staining and NOX activity measurements. In contrast, oxidative stress induced by 150 mM NaCl was more efficiently prevented, as indicated by low malondialdehyde (MDA) levels and especially at 7 days, by increased levels of SOD, POX, APX, and GR. However, at 300 mM NaCl, decreased levels of protective enzymes such as SOD, CAT, POX, and GR, particularly with long-term stress (14 days), resulted in limited ROS scavenging activity and increased MDA levels. Moreover, at 300 mM NaCl, the high H2O2 content caused oxidative damage rather than inducing protective responses against H2O2. These results suggest that S. kotschyana is potentially tolerant to salt-induced damage only at low salt concentrations.Selcuk University Scientific Research Projects Coordinating OfficeSelcuk University [11401069]Financial support for this work was provided by Selcuk University Scientific Research Projects Coordinating Office (Project number: 11401069). We gratefully thank to Dr. Mirza Hasanuzzaman Assist. Prof., department of Agronomy, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh, for his recommendation on performing on analysis of tAsA and tGlut contents and language correction. We also would like to thank to Dr. Mehmet Hamurcu Assist. Prof., for his technical assistance on ICP-OES analyses

Exogenous progesterone application protects chickpea seedlings against chilling-induced oxidative stress

This experiment was conducted to monitor the influence of foliar progesterone application on the chilling tolerance of chickpea seedlings. Twelve-day-old chickpea seedlings were treated with 10(-7) mol L-1 progesterone. After 12 h, the seedlings were exposed to day/night temperatures of 9/5 A degrees C for 72 h in a growth chamber. Chilling stress resulted in remarkable increase in the activities of antioxidant enzymes including superoxide dismutase (SOD), guaicol peroxidase (POX), catalase, ascorbate peroxidase (APX) and glutathione reductase, as well as the level of antioxidant compounds like ascorbic acid, glutathione and proline. In a similar manner, chilling stress affected significantly oxidative stress indicators measured as superoxide production, electrolyte leakage, hydrogen peroxide (H2O2) and malondialdehyde contents. The values of these parameters were lesser in progesterone-applied seedlings that were associated with higher activities of antioxidant enzymes and greater levels of antioxidant compounds in these seedlings. A highly significant correlation was recorded between SOD, POX and APX activities and their isozymes. This correlation confirmed enhanced activities of these enzymes. In addition, progesterone application ameliorated chilling-induced decrease in relative leaf water content (RLWC) and chlorophyll content. Freezing tolerance, showed by thermal analysis method, proved that progesterone application improved chilling tolerance of chickpea seedlings by lowering freezing point from -4 to -5.5 A degrees C. It is possible that chilling tolerance induced by progesterone is related to elevation of RLWC, chlorophyll content and antioxidative activity, and thereby decrease in oxidative stress indicators