METABOLIC IMPLICATIONS OF SALT INDUCED OSMOLYTE ACCUMULATION IN AVICENNIA MARINA

摘要

Salt induced solute accumulation is a well known feature for osmotic adjustment in plants under salt stress.Concomitantly, synthesis of compatible osmolytes requires energy which may compromise plant growth. This studyhighlights the contribution of different solutes to leaf osmolality in Avicennia marina seedlings and saplings and possiblemetabolic shifts under saline conditions. Salinity was imposed using different seawater strengths (0, 50% & 150% seawatersalinity) to evaluate contribution of ions and organic osmolytes and their possible effects on plant growth. Optimum growthwas found in 50% seawater salinity (SWS) and decreased under salt stress (150% SWS). Low values for water and osmoticpotential could be accounted for an increase in the amount of Na+ which appeared to contribute the most in leaf osmolalityin both seedlings (38%) and saplings (43%) under saline conditions. Among tested organic solutes, the contribution of totalsoluble sugars (TSS) was higher in non-saline control and moderate salinity, followed by glycinebetaine (GB) while proline(PRO) values were lowest. The amount of GB increased to a 4 fold in seedlings and 2 fold in saplings under salt stress. Theincreased ratio of GB:TSS in seedlings under salt stress indicates their sensitivity over saplings and a likely metabolic shiftat the cost of growth.