Morphogenic and biochemical responses of Bacopa monniera cultures to zinc toxicity

This study. investigates the effect of zinc on morphogenic and biochemical responses of Bacopa monniera (L.) Wettst and determines the maximum zinc le vel to which tolerant cultures could be raised. Incorporation of zinc sulfa te (100-600 mu M) in the maintenance medium, i.e., Murashige: and Skoog's ( MS) medium (sucrose 2%) supplemented with naphthaleneacetic acid (0.2 mg l( -1)). br benzylaminopurine (0.5 mg l(-1) ) and glutamine (50 mg l(-1) ')1 p romoted growth of regenerants. Higher concentrations (800-1000 mu M). howev er, inhibited shoot and root growth for 16 weeks. Thereafter., the regenera nts resumed normal growth th even on higher concentrations. Morphogenic res ponse in terms of number, height of shouts, fresh weight;eight of regeneran ts and root differentiation uas monitored. Proline and protein accumulated as a sequel to zinc stress. The rate of photosynthesis was enhanced by the appl appropiate supply; of ZnSO4,. The amount of ZnSO4, accumulated at the cell wall aas considerably higher than that in the cytoplasm. The cultures growing on ZnSO4,-supplemented medium for the last 3 years, could not survi ve when;hen transfered to ZnSO4-free (control) media, thus indicating their adaptation towards zinc stress.;(C) 1999 Elsevier Science Ireland Ltd. All rights reserved.