Exogenous Proline Application Reduces Phytotoxic Effects of Selenium by Minimising Oxidative stress and Improves Growth in Bean (Phaseolus vulgaris L.) Seedlings

Abstract

Bean (Phaseolus vulgaris L.) seedlings were subjected to varying selenium levels (1, 2, 4, and 6 ppm) in a hydroponic culture. The germination reached 100% in 48 h in all Se levels except 6 ppm, where it took 72 h. The root and shoot growth was stimulated at 1 and 2 ppm Se levels that was commensurate with increase in chlorophyll content, leaf water content, and cellular respiration. At 4 and 6 ppm Se levels, the growth was inhibited appreciably, which was associated with increase in stress injury measured as damage to membranes and decrease in cellular respiration, chlorophyll, and leaf water content. The oxidative injury as elevation of lipid peroxidation was larger compared to hydrogen peroxide accompanied by reduced levels of enzymatic (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and non-enzymatic (ascorbic acid and glutathione) antioxidants. Proline content was significantly higher at 1 and 2 ppm Se but diminished considerably at 4 and 6 ppm levels concomitant with the reduced growth. Exogenous application of proline (50 µM) resulted in substantiation of its endogenous levels that antagonised the toxic effects of Se by improving the growth of seedlings. The stress injury was reduced significantly with simultaneous increase in enzymatic and non-enzymatic antioxidants. Especially the components of ascorbate-glutathione cycle showed larger stimulation with proline application. The role of proline in mitigating the toxic effects of Se is discussed.

Proline induces heat tolerance in chickpea (Cicer arietinum L.) plants by protecting vital enzymes of carbon and antioxidative metabolism

“…The decrease in extent of oxidative stress in proline-treated seedlings might have occurred due to elevation in levels of antioxidants. In this regard, our findings are in line with the observations on salt-stressed cultured tobacco cells (Hoque et al (2007a, b), olive plants (Ben Ahmed et al 2010) and selenium-stressed bean plants (Aggarwal et al 2010) where proline application resulted in reduction in oxidative damage. In these cases, the stressed plants showed improvement in the activities of enzymatic antioxidants such as superoxide dismutase, catalase, ascorbate peroxidase and polyphenol oxidase.…”

Foliar Spray of Proline Enhanced the Photosynthetic Efficiency and Antioxidant System in Brassica juncea

“…The symbol "*" in the figures depicts that the data is significant chlorophyll molecules are the membrane bound structures whose stability depends highly on the integrity of the membrane structure which is possibly maintained in this study by proline as it acts as a membrane stabilizer (Ashraf and Foolad, 2007). These studies are in conformity with other crops (Ahmed et al, 2011;Aggarwal et al, 2011;Wani et al, 2012).…”

Mechanisms of the Selenium Tolerance of theArabidopsis thalianaKnockout Mutant of Sulfate Transporter SULTR1;2

“…This is consistent with the result that sultr1;2 is more tolerant of Se stress than the wild type. MDA contents of P. vulgaris 5) but the present study indicates that Se stress decreased the MDA contents of sultr1;2. Besides, Cd stress increases the MDA contents of P. vulgaris 29) but Cd stress decreases the MDA contents of Phaseolus coccineus.…”

“…Se at higher doses induces lipid peroxidation, including the formation of malondialdehyde (MDA), 3) and inhibits the growth of most plants, including A. thaliana, 4) whereas at lower doses it can improve the growth of certain plants, including Phaseolus vulgaris, under stress. 5) This improvement can be attributed to the increased activities of antioxidant enzymes, superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6), and peroxidase (POX, EC 1.11.1.7). Moreover, reactive oxygen species (ROS) production induced by Se was suppressed in an Se hyperaccumulator, Stanleya pinnata.…”