Differences in the activities of some antioxidant enzymes and in H2O2 content during rhizogenesis and somatic embryogenesis in callus cultures of the ice plant.

Callus was obtained from hypocotyls of Mesembryanthemum crystallinum seedlings cultured on two types of medium-germination medium (GM) and callus induction medium (CIM). Following subculture on shoot induction medium SIM1, the callus formed on CIM medium regenerated roots or somatic embryos, while that obtained on GM medium was non-regenerative. The activities of CuZn-superoxidase dismutase (SOD) were comparable in all calli, but the activities of FeSOD and MnSOD varied according to the activity of photosystem II and the regenerative potential of the tissues. Catalase (CAT) activity was related to H2O2 concentration and affected by both the culture conditions and the morphogenic potential of the calli. The possible role of CAT, SODs and H2O2 in the regeneration of M. crystallinum from callus is discussed.