Chromium toxicity, physiological responses and tolerance potential of lemon grass (Cymbopogon flexuosus Nees ex steud. wats.)

Abstract

The present investigation describes the physiological and biochemical response of  Lemon grass (Cymbopogon flexuosus Nees ex Steud.Wats.) to increaseing doses of hexavalent chromium (Cr⁶⁺⁾ grown  under in vivo  pot culture experiments.  Plantlets of lemon grass were transplanted in poly bags and grown for 10 days in uncontaminated 5 kg garden soil. After 10 days the plantlets were grown for 60 days supplemented with different concentrations of Cr⁺⁶(10 mg Kg^-1, 50 mg Kg^-1, 100 mg Kg^-1 and 200 mg Kg^-1respectively). The plants grown in terms of length and biomass was analysed for toxicological impacts using varying degrees of Cr⁺⁶ by soil contamination. Although the plant survival was  100% (using all  the treatments  upto 50 ppm application of Cr⁺⁶), the root and  shoot toxicity, root and shoot tolerance  values decreased significantly with increasing concentrations of Cr^+6. The toxicological values were clearly correlated with the growth measures induced by Cr⁺⁶ ions in contaminated soil. The leaf pigments (chlorophyll & carotenoids), total protein, catalase and different carbohydrate fractions exhibited declining trend with increasing Cr⁺⁶ ions. However,   accumulation of proline and enhanced peroxidase activity was due to plant protection device under chromium stress. One of the most important observations was that  the lemon grass  do  not tolerate  beyond toxic  50 ppm concentration of Cr⁺⁶ beyond which the effects becomes chronic  for which  the plants  could not survive upto 60 days growth. This observation  suggests  the thriving potentiality  of  lemon grass at sub toxic levels which can  be exploited in  future  for  phytoremediation  experiments and  field application in mine waste soil for reclamation.