Physiological and genetic effects of chromium (+VI) on toxitolerant lichen species, Pyxine cocoes.

Chromium is a highly toxic non-essential metal, which causes a variety of metabolic activities in plants. Pyxine cocoes a well known toxitolerant lichen species was considered to evaluate the possible physiological, biochemical, and genetic changes that occur due to chromium Cr (+VI) stress. The physiological (chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein, and Fv/Fm) and genetic (ISSR-PCR and ITS) parameters were used to estimate the changes in P. cocoes. Different concentrations of Cr (+VI) (0, 10, 25, 50, 75, and 100 μM) for 10, 20, 30, and 45 days were employed on transplanted lichen species. The results revealed that the exposure of Cr (+VI) for 10, 20, 30, and 45 days under controlled conditions caused a significant decline in physiological processes with increasing metal stress. Amino acid profile at different concentrations on the 45th day too indicated prevailing stress condition as proline content significantly increased at 100 μM concentration. Inter-simple sequence repeat (ISSR) and internal transcribed spacer (ITS) techniques were used to evaluate the genotoxicity induced by chromium stress. ISSR profiles showed a consistent increase in appearance and disappearance of bands with increasing concentration of the chromium. ISSR technique, therefore, is more sensitive and reproducible to study polymorphism induced by environmental stress. The present study revealed that the physiological and genetic changes induced by the Cr (+VI) can be used as a tool to study environmental stress and polymorphisms due to genotoxicity. To the best of our knowledge, application of ISSR-PCR and ITS sequences in toxitolerant species (P. cocoes) appears to be the maiden attempt to evaluate the genotoxicity.