PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES OF MUNGBEAN (VIGNA RADIATA L. WILCZEK) TO VARYING CONCENTRATIONS OF CADMIUM CHLORIDE OR SODIUM CHLORIDE

The present study focuses on the physiological and biochemical responses of Vigna radiata seedlings to varying concentrations of
CdCl2 and NaCl. Both the stressors enhanced seedling mortality, more notably at the higher concentrations. The detrimental effects
were reflected in the form of decline in normal growth, reduction in germination percentage, inhibition in root and shoot length,
decreased fresh weight and dry weight of seedlings and loss in chlorophyll content. The severity of stresses increased in a dosedependent
manner. Both CdCl2 and NaCl provoked oxidative stress as detected by enhanced malondialdehyde (MDA) and peroxide
content, being proportionate with the concentration of the stressors. In terms of susceptibility to the two stresses, both roots and leaves
showed similar response. As a protective mechanism, the seedlings showed elevated levels of the osmoregulator proline, the increment
being somewhat higher in roots for NaCl, while similar enhancement in both roots and leaves for CdCl2. The activities of the
antioxidant enzymes, catechol-peroxidase (POX) and catalase (CAT) increased progressively with the increase in CdCl2 and NaCl
concentrations. While the increment was greater in roots for catechol-POX, it was higher in leaves for CAT. The increase in
antioxidant activities could either be a response to the cellular damage induced by the stressors or a mechanism to ward off the
damages due to lipid peroxidation (enhanced MDA) and increased peroxide. Thus, by altering the level of biomolecules, and
modulating their physiological and biochemical functions, Vigna radiata seedlings could overcome the cellular toxicity rendered by
CdCl2 and NaCl.


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