Physiological responses of Alternanthera philoxeroides (Mart.) Griseb leaves to cadmium stress.

Aquatic macrophytes were found to be the potential scavengers of heavy metals from aquatic environment. In this study, several physiological responses of Alternanthera philoxeroides (Mart.) Griseb leaves to elevated concentrations of cadmium (up to 10mM) were investigated. It was found that A. philoxeroides was able to accumulate cadmium in its leaves. The pigment contents decreased with the increase of the Cd concentrations. The Cd could induce rise of the activity of peroxidase (POD) at lower concentration (<5mM), however, when the concentration of Cd rose up to 10mM, the POD activity declined. The changes of superoxide dismutase (SOD) and Catalase (CAT) activities were exactly opposite to that of POD. In the leaves of Cd-treated fronds, the amounts of three polypeptides with apparent molecular weights 80, 39 and 28kDa, respectively, were became visible in SDS-PAGE. The nature of these polypeptides remains to be determined.

[Studies on tissue culture of Dendrobium lituiflorum].

OBJECTIVE: To select optimal media and conditions for the tissue culture of Dendrobium lituiforum. METHOD: The basic media, light illumination condition, phytohormone, and natural aqueous extracts. were tested and compared. The chlorophyll contents and soluble protein contents were measured. RESULT: N6 medium was suitable for embryo germination and growth. 1/2 MS + NAA 0.5 mg x L(-1) cordd be used as the optimal protocorm multiplying media. Culture 20 days in darkness in advance, and then in light is useful to embryo germinate. 1/2 MS+ NAA 0-0.5 mg x L(-1) is beneficial to protocorm multiplication largely. N6 + 6-BA 2.0 mg x L(-1) + NAA 0.5 mg x L(-1) + 10% potato juice is useful to protocorm differentiation. Phytohormone and potato juice added to the media promoted chlorophyll content and souble protein content. N6 + NAA 0.5 mg x L(-1) + 10% banana juice is the best medium for plantlet rootage and strengthening. CONCLUSION: Concentration of inorganic salt, nitrogen source and illumination condition are important to embryo germination and growth. The nitrogen source type has effect on the protocorm multiplication. The chlorophyll contents and souble protein contents may be index to indicate the growth condition of plantlets, which can help to select the optimal media.