Exogenous jasmonic acid enhances oxidative protection of Lemna valdiviana subjected to arsenic

Oxidative damage is one of the most harmful effects arising from arsenic (As) toxicity in plants. Herein, the role of exogenous jasmonic acid (JA) in the modulation of As-induced oxidative stress in Lemna valdiviana was investigated. Plants were grown for 24 h in Clark's nutritive solution containing As (4.0 mg L-1) or As + JA (50, 100, 250 and 500 mu M). Chlorophyll a and b content decreased under As stress, either in isolation or associated with JA. The decreased chlorophyll a/b ratio in As-exposed plants was recovered by JA treatment at 100 mu M. The carotenoid content was higher in plants exposed to As compared to controls and lower when it was associated with JA. Arsenic triggered the accumulation of O-2(center dot-) and H2O2, in addition to severely increasing lipid peroxidation. Application of JA in As-grown plants resulted in lower O-2(center dot-) content and lipid peroxidation than in those grown under As alone, as a result of enhanced SOD activity. On the other hand, H2O2 accumulation was increased by JA in As-stressed plants, associated with higher CAT, POX and GPX activity. The As content and bioaccumulation factor (BF) were improved by application of JA in the nutritive solution at 250 and 500 mu M. Our findings indicate that JA modulates the pigment balance, thereby fine-tuning energy dissipation as well as alleviating As-induced oxidative damage in L. valdiviana through modulation of ROS homeostasis and improvement of the antioxidant enzymatic system, allowing increased accumulation of As without showing major damage.