Assessment of Osmolyte Accumulation in Heavy Metal Exposed Salvinia natans

Accumulation of osmolytes in terrestrial plants in response to environmental stresses is well reported and information about aquatic plants is limited. Present study aimed to investigate if the aquatic weed, Salvinia natans accumulates osmolytes/compatible solutes on exposure to various heavy metals. Plants exposed to heavy metals viz. Cd, Cu, Ni, Cr, Mn, Fe, Co, Pb and Zn, were harvested after 48 h and various osmolytes including sucrose, mannitol, proline, glycine betaine and polyamines were estimated using biochemical methods. Results suggested that heavy metal stress does trigger the accumulation of osmolytes such as sucrose, mannitol and glycine betaine. In contrast proline accumulation was not observed. Studies of heavy metal stress on the endogenous levels of polyamines showed presence of free polyamines, while conjugated and bound forms were not detected. Among free polyamines, Putrescine (Put) and Spermidine (Spd) did not show significant decrease in heavy metal exposed Salvinia except Pb and Fe exposed plants. Spermine (Spm) content showed decline in heavy metal exposed Salvinia. The decrease in polyamine levels indicated their possible role in combating oxidative stress induced by heavy metals. Studies suggest that accumulation of osmolytes under heavy metal stress might help in imparting tolerance in Salvinia.