Published Paper Details:

The toxicant cadmium chloride showed all the features of heavy metal toxicity on a blue-green alga, where the metal showed dual behavior like stimulation and good recovery at sub-lethal concentration and inhibition followed by no recovery at higher lethal concentrations. The present piece of work aims at understanding the impact of cadmium chloride on the activities of two important enzymes like nitrate reductase and nitrogenase of a blue-green alga in vivo. The Nitrate reductase activity of the control set remained static within the standard deviation range with the increase in exposure period. At sub-lethal conc.-X, a maximum of 27.08% increase in the enzyme activity was marked on 15th day of exposure and when the exposed alga was transferred to toxicant free medium 18.37% increase was noted on 15th day of recovery. At higher lethal concentrations of cadmium chloride significant depletion in the enzyme activity was observed showing inhibitory action of the toxicant cadmium chloride. The nitrogenase activity of the control set remained static within the standard deviation range with the increase in exposure period. At sub-lethal conc.-X, a maximum of 5.05% decrease in the enzyme activity was marked on 15th day of exposure and when the exposed alga was transferred to toxicant free medium 7.87% decrease was noted on 15th day of recovery. At higher concentration, a maximum of 90.8% decrease in enzyme activity was marked on 9th day of exposure and with the increase in exposure period 100% decrease was noted and when the exposed alga was transferred to toxicant free medium. 100% decrease in the enzyme activity was noted on 15th day of recovery indicating no recovery was noted. The toxicant, Cadmium chloride significantly affected both the enzymes and the regulatory action of both the enzymes was lost in the process and the exposed alga could not resist the heavy metal toxicant and ultimately died at higher concentrations.