Characterization of Chl a Fluorescence of Hydrophytes under Cadmium Stress

The effects of Cd²⁺ ions on the Chl a fluorescence of 5 hydrophytes (e.g. Lemna, Salvinia, Ricciocarp, Nymph, Typha plants) were investigated in order to select Cd²⁺ -sensitive plant species and to get informations on physiological responses of plants to Cd²⁺ stress. Lemna plants were most sensitive to cadmium stress, while Nymph plants were tolerant. However, in all Cd²⁺ -treated plants, Fv/Fm, the maximum photochemical efficiency of PS II, decreased in proportion to the increase of Cd²⁺ concentration and treatment time. The Chl a fluorescence transient O-J-I-P was also considerably affected by Cd²⁺ ions; the fluorescence yield decreased consid- erably in steps J, I and P in Cd²⁺ treated plants, although it followed a typical polyphasic rise in non-treated plants. In Lemna plants, the functional parameters, ABS/CS, TRo/CS와 ETo/CS and RC/CS, decreased in proportion to the increase of Cd²⁺ concentration, while N, Mo and Kn increased. The structural parameters, Φpo , Φpo /( 1-Φpo ), Plabs, SFlabs, Kp and RC/ABS, also decreased according to the increase of Cd²⁺ concentration. Consequently, Lemna plants will be useful as a experimental model system to investigate responses of plants. And several functional or structural parameters could be applied to determine quantitatively the physiological states of plants under stresses.