Phytotoxicity of cadmium ions on germinating seedlings of mung bean {Phaseolus vulgaris): Involvement of lipid peroxides in chlorophyll degradation -Physiol. Plant. 85: 85-89.Germinating seedlings of mung bean {Phaseolus vulgaris L. cv. K-16) were treated with different concentrations of cadmium acetate (10, 50 and 100 nM), Cd'* lowered the chlorophyll and heme levels. The level of lipid peroxides were higher on day 3 than on day 6. However, Cd*^ treatment significantly enhanced the level of lipid peroxides. Similarly, a dose-dependent induction of lipoxygenase (EC 1.13.11.12) activity was observed with Cd-* treatment. Further, the activities of antioxidant enzymes such as superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6) were decreased. Our results suggest that lipoxygenase-mediated accumulation of lipid peroxides on the one hand and inhibition of free radical scavenging enzymes like superoxide dismutase and catalase on the other caused a pronounced reduction in the chlorophyll and heme levels of the seedlings. The experiments conducted on the effect of Cd"^ on dark-grown seedlings did not conform with the result of light-grown seedlings. Though chlorophyll and heme levels decreased in a dose-dependent manner, no accumulation of lipid peroxides was observed. Suggesting that the inhibition of chlorophyll synthesis by Cd^* is achieved both by reaction with constituent biosynthetic enzymes as well as peroxide-mediated degradation.

In vitro grown callus and seedlings of Brassica juncea were treated with equimolar concentrations of cadmium and compared for their respective tolerance to cadmium. Calli cultures were grown on Murashige and Skoog medium supplemented with alpha 6-benzyl aminopurine (200 microg (-1), naphthalene acetic acid 200 microg L(-1)) and 2,4-dichloro-phenoxy acetic acid (65 microg L(-1)) while the seedlings grown on Hoagland's nutrient solution have been carried out. Cellular homeostasis and detoxification to cadmium in B. juncea were studied by analyzing the growth in terms of fresh weight and dry weight, lipid peroxidation, proline accumulation, and antioxidative enzymes (superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT)). At 200 microM cadmium, callus and seedlings showed 73.61% and 74.76% reduction in tolerance, respectively. A significant increase in malondialdehyde (MDA) content was found in both calli and seedlings; however, the amount of MDA content was more in seedlings. Proline content increased on lower concentration of cadmium (up to 50 microM), and it further decreased (up to 200 microM). But the accumulation of proline was higher in callus cultures. The overall activity of antioxidative enzymes (SOD, CAT, and APX) was found to be higher in callus in comparison to seedlings of B. juncea. Callus and seedlings showed a significant (P

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