Ameliorative role of nitric oxide on H2O2 toxicity to a chlorophycean alga Scenedesmus obliquus

Abstract

A concentration-dependent toxicity of hydrogen peroxide (H2O2) was observed on growth yield, chlorophyll a content and chlorophyll fluorescence characteristics of the green microalga Scenedesmus obliquus under laboratory batch culture conditions. The addition of sodium nitroprusside, a nitric oxide (NO) donor, in combination with H2O2 prevented chlorophyll losses, and the inhibition level of growth yield, maximum quantum yield of photosystem II (PSII) and the light-adapted quantum yield of PSII were significantly reduced. The antioxidant compounds, penicillamine and thiourea also reduced the damage caused by H2O2 exposure. The protective actions of sodium nitroprusside were, however, arrested in cultures where sodium nitroprusside was supplemented in combination with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO), a specific scavenger of NO. The NO3113-grown Scenedesmus depicted less sensitivity to H2O2 toxicity with respect to the quantum yields of PSII as compared to its NH4+-grown counterpart. The role of NO in providing protection against H2O2 toxicity to the processes under study was discussed.