The present study was undertaken to test the influence of exogenously applied jasmonic acid (JA) upon the growth and metabolism of Wolffia arrhiza (Lemnaceae), the smallest vessel aquatic plant exposed to lead (Pb) stress. It was found, that JA acted in a concentration-dependent manner. Treatment with JA at the highest concentration 100 mu M resulted in the enhancement of heavy metal toxicity leading to increase in metal biosorption and formation of lipid peroxides as well as decrease in fresh weight, chlorophyll a, carotenoid, monosaccharide and soluble protein content. In contrast, this phytohormone applied at 0.1 mu M protected W arrhiza fronds against Pb stress inhibiting heavy metal accumulation, restoring plant growth and primary metabolite level. Moreover, JA at 0.1 mu M activated enzymatic (catalase, ascorbate peroxidase, NADH peroxidase) and non-enzymatic antioxidant (ascorbate, glutathione) system in W arrhiza, and therefore, suppressed oxidative destruction of cellular components induced by heavy metal. The data suggest that JA plays an important role in the growth and metabolism of W arrhiza exposed to abiotic stressor and its high adaptation ability to metal contamination of aquatic environment. (C) 2009 Elsevier B.V. All rights reserved.
