Arsenic is a critical contaminant that is released into the environment through geochemical processes and anthropic actions. Two independent hydroponic experiments were performed to evaluate the ecophysiological responses of water hyacinth [Eichhornia crassipes (Mart.) Solms] to As under various stress conditions. In experiment 1, water hyacinth was exposed to As5+ at concentrations of 0, 0.2, 2.0, and 20 mg L-1 for 0, 2, and 4 d; in experiment 2, water hyacinth was exposed at concentrations of 0, 0.025, 0.05, and 0.1 mg L-1 for 0, 10, and 20 d. In both experiments, As accumulation in plant tissue was proportional to its increase in the nutrient solution; As concentrations were higher in roots than in shoots. Detrimental effects of As on gas exchange were observed and were more pronounced in experiment 1. In experiment 1, at the beginning on the second day of exposure, significant decreases of maximum photochemical efficiency of PSII (Fv/Fm), variable chlorophyll fluorescence (Fv/F0), and photosynthetic pigment contents were observed in plants exposed to 2.0 and 20 mg(As5+) L-1. It indicated that damage to the photosynthetic apparatus had occurred. No changes in Fv/Fm, Fv/F0, and contents of photosynthetic pigments were observed in the plants grown in the presence of 0.2 mg(As5+) L-1 (in experiment 1) or after any of the treatments in experiment 2, indicating plant tolerance. Elevated nonphotochemical quenching was observed in experiment 2 after 20 d of exposure to As; it was as a part of protection mechanisms of the photosynthetic apparatus in these plants. The results obtained here indicate that the use of water hyacinth for As5+ removal from highly impacted environments is limited but that it is effective in remediating sites with a low contamination., A. C. Meneguelli-Souza, A. P. Vitória, T. O. Vieira, M. S. O. Degli-Esposti, C. M. M. Souza., and Obsahuje seznam literatury
Zinc (Zn) plays an important role in the physiological processes in plants and may mitigate trace element stress. The aim was to evaluate the morphophysiological responses of Alternanthera tenella plants exposed to cadmium (Cd) and Zn under in vitro conditions. Segments of A. tenella were transferred to flasks containing medium supplemented with different combinations of Cd (0, 75, or 150 μM) and Zn (0, 750, or 1,500 μM) concentrations, totalizing nine treatments. We assessed the growth traits, anatomy, chlorophyll a fluorescence by OJIPs, and tolerance index (TI). With exposure only to Cd, the plants showed physiological disorders. Zn supplementation in the medium had a positive effect on the physiological performance of plants. At concentrations ≤ 750 μM, it can partially mitigate the deleterious effects of Cd. Plants grown with Cd and Zn showed intermediate TI. The results proved the potential of Zn as a mitigator of Cd-induced stress in plants.