Tissue diversity in respiratory metabolism and free radical processes in embryonic axes of the white mangrove (Avicennia marina L.) during drying and wet storage

Species diversity in responses to desiccation in plants is well studied and documented. However, organ and tissue variability in plant dehydration responses is not as well investigated and understood. Therefore, the responses of whole axes, hypocotyls, root primordia and plumules of white mangrove to drying and wet storage were monitored. Increasing the rate of drying lowered the critical and lethal water concentrations for survival as assessed by germination capacity and tetrazolium staining. Dehydration and hydrated storage were generally associated with decrease in activities of phosphofructokinase (PFK) and malate dehydrogenase and levels of nicotinamide adenine dinucleotide and an increase in the levels of hydroperoxides in whole axes, hypocotyls, root primordia and plumules and membrane damage in axes. Increase in the activities of superoxide dismutase and catalase and decrease in the activities of glutathione reductase and amounts of ascorbate accompanied drying and moist storage in all tissues, in general. Apart from the activity of PFK, the plumules showed the highest activities and quantities of all the enzymes and compounds among the tissues during desiccation and wet storage. It is possible that this tissue, despite its relatively small size and volume plays disproportionately an important role in the events described. Nonetheless, it is likely that physical rather than metabolic damage underlined loss of viability as it occurred at high water concentration.