[Effects of Ni2+ on physiological characteristics and submicroscopic structure of Salvinia natans leaves].

Influence of 0, 5, 10, 15, 20 mg/L Ni2+ on growth, mineral nutrition, chlorophyll, carotenoid, soluble protein, soluble sugar, superoxide (O2*-), hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents as well as the activities of superoxide dismutase (SOD), guaiacolperoxidase (POD), and catalase (CAT) were studied in the leaves of Salvinia natans plants on 10 days after treatment. With the increase of the Ni2+ concentrations, exposure of the plants revealed that, (1) the addition of Ni2+ affected the absorption of mineral nutrients, it mainly increased the absorption of Ca2+, Na+, Zn2+, Fe3+ and Mg2+, while reduced that of Mn2+, Mo2+, P and K+. (2) The content of chlorophyll, carotenoid, soluble protein and soluble sugar content as well as activities of SOD and CAT decreased gradually. That of O2*-, H2O2 and MDA content as well as POD activity increased, 383%, 168%, 207%, 131% of these controls, respectively. (3) In the leaves of Ni2+ -treated fronds, the polypeptide with apparent molecular weights 94000, was became visible in SDS-PAGE, and the nature of it remains to be determined. The amount and intensity of polypeptide band increased gradually with augment of Ni2+ was also observed, the polypeptide with apparent molecular weight 35,000 increased significantly in fronds. (4) Transmission electron microscope observation indicated that Ni2+ also imposed injury action on submicroscopic structure of leaf cells, disaggregation of nucleolus, agglutination and disappearance of chromatin of nucleus, disruption of nuclear membrane, swelling of thylakoids and breakage of chloroplast envelope, decreasing of cristae quantity and vacuolization of mitochondria. The conclusion could be reached that the plant death was resulted from destruction under structure foundation of physiological function, unbalance of ion equilibrium and disorder of physiological metabolism.

[Effects of Cu2+ stress on leaf physiological indice and ultrastructure of Potamogeton malaianus].

With solution culture, this paper studied the toxic effects of different concentrations of Cu2+ (0, 2, 4, 6, and 8 mg x L(-1)) on the chlorophyll content, soluble protein content, protective enzyme activities, active oxygen generation, and ultrastructural changes in Potamogeton malaianus leaf. The results showed that with increasing concentration of Cu2+, the chlorophyll, carotenoid and soluble protein contents and superoxide dismutase (SOD) and peroxidase (POD) activities decreased, catalase (CAT) activity increased first and decreased then, while O2-*, H2O2, MDA and soluble sugar content increased. SDS-PAGE revealed that Cu2+ induced the disappearance or the decrease of the expression amount of four polypeptides with apparent molecular weights of 60.9, 18.8, 15.7, 22.3 and 30.0 kDa. Transmission electron microscopy observation indicated that the higher Cu2+, concentration, the more serious damages the leaf organelles, especially chloroplast, mitochondria and nucleus, suffered. It was concluded that the death of P. malaianus plant under Cu2+ stress was resulted from the destruction of physiological function and structural foundation, and the disorder of physiological metabolism. The lethal concentration of Cu2+ could be 2-4 mg x L(-1).