Glutathione Levels and Physiological Responses of Chromium-Stressed Seedlings of Brachiaria Ruziziensis and B. Brizantha.

Chromium toxicity is a matter of increasing concern for pasture growing in Brazil. Such a stress influences redox reactions within plant cells and, thus, generates detrimental reactive oxygen species. Glutathione (GSH) is a peptide that acts as an antioxidant within cells, and has been reported to mitigate chromium toxicity in many species. In this study, Brachiaria brizantha and B. ruziziensis seedlings were evaluated for GSH production and physiological responses following addition of 0 or 5 mg.L^-1 Cr(III) to the nutrient solution. GSH levels were determined by colorimetric analysis at 412 nm using DTNB (5,5’-dithio-bis(2-nitrobenzoic acid)) and recovery with glutathione reductase. Evaluations were performed at days 10 and 20 (under continuous growth) and analyzed through ANOVA. The essays were carried out in a complete randomized design with 4 replications, arranged in a 2 (plant species) X 2 (chromium level) X 2 (days 10 and 20) factorial. Results revealed that Cr(III) effected an averaged increase of 0.77 mg.g^-1 in GSH levels, with a more pronounced response of B. ruziziensis. Physiological indicators were depressed in day 20, markedly in B. brizantha. It is concluded that the addition of Cr(III) to the growing medium causes GSH levels to rise, and this effrect is more evident in B. ruziziensis. Cr(III) effects on physiological processes, in turn, are more conspicuous in B. brizantha.