Methylmethionine (Vitamin U) alleviates negative effects of chemical stressors on photosynthesis of the green alga scenedesmus opoliensis

Abstract

Investigation of stress tolerance in unicellular algae represents an experimental approach that contributes to elucidation of cellular events related to stress-induced metabolic and developmental reactions in plants. In this context, we investigated the interaction of methylmethionine (vitamin U) with environmental stress factors (high concentrations of heavy metals, herbicides) in photosynthetic energy conversion, net oxygen evolution and dry biomass production of the green microalga Scenedesmus opoliensis. Parameters of the induced chlorophyll fluorescence reveal the benefic influence of vitamin U on light use efficiency of photochemical reactions, as well as on the organization of light-harvesting pigment-protein complexes of the thylakoid membranes in algal cells exposed to micromolar concentrations of cadmium. Oxidative damage caused by the herbicide methylviologen is diminished by methylmethionine. The activities of ascorbate peroxidase and superoxide dismutase are enhanced in the algal cells exposed to the combined effect of methylviologen and vitamin U. In the absence of stress factors, vitamin U has no significant influence on the investigated physiological parameters. Further studies on the protective role of methylmethionine in the presence of stress factors may provide a better insight into the mechanisms of antistress reactions of plants grown in unfavorable environments.