Copper Effects on Photosynthetic Activity and Membrane Leakage of Azolla filiculoides and A. caroliniana

The toxic effects of copper on the photosynthetic apparatus and cell membrane stability of Azolla species were evaluated by means of the chlorophyll fluorescence, leakage of electrolytes and total phenolic compounds. Different collects from Azolla filiculoides (Xalapa & Ensenada) and A. caroliniana (CEG) were incubated with different Cu2+ concentrations (0.02, 0.2, 1 & 2 mM) for 36 h in a plant growth chamber. The results showed that treatments with higher Cu concentration (1 & 2 mM) presented clear signs of disrupted photosystem II, since the potential photochemical yields (Fv/Fm) were lower than the control responses. However, membrane permeability (leakage of electrolytes) of both species significantly enhanced with the increase in Cu concentration after 12 h of exposure. Additionally, total phenolic constituents of both species did not differ significantly by Cu concentrations excepting for lower doses of Cu (0.02 mM) after 36 h of exposure. In conclusion, chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early changes in photosynthetic performance of Azolla in response to heavy metal pollution. © 2010 Friends Science Publishers