Abstract
This study investigates the effect of zinc on morphogenic and biochemical responses of Bacopa monniera (L.) Wettst and determines the maximum zinc level to which tolerant cultures could be raised. Incorporation of zinc sulfate (100–600 μM) in the maintenance medium, i.e., Murashige and Skoog’s (MS) medium (sucrose 2%) supplemented with naphthaleneacetic acid (0.2 mg l−1), benzylaminopurine (0.5 mg l−1) and glutamine (50 mg l−1), promoted growth of regenerants. Higher concentrations (800–1000 μM), however, inhibited shoot and root growth for 16 weeks. Thereafter, the regenerants resumed normal growth even on higher concentrations. Morphogenic response in terms of number, height of shoots, fresh weight of regenerants and root differentiation was monitored. Proline and protein accumulated as a sequel to zinc stress. The rate of photosynthesis was enhanced by the appropriate supply of ZnSO4. The amount of ZnSO4 accumulated at the cell wall was considerably higher than that in the cytoplasm. The cultures growing on ZnSO4-supplemented medium for the last 3 years, could not survive when transferred to ZnSO4-free (control) media, thus indicating their adaptation towards zinc stress.
Keywords
Bacopa monniera; Morphogenic response; Photosynthesis; Proline; Protein; Zinc toxicity
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