Responses of the mangrove Rhizophora mucronata to high salinities and low osmotic potentials

Abstract

The effect of solutions of seawater or non-saline polyethylene glycol (PEG)-6000 on dry mass, tissue water potential, stomatal resistance and inorganic solute uptake were investigated in the mangrove, Rhizophora mucronata Lam. Plants were treated with solutions of seawater or PEG-6000 at osmotic potentials of − 0,05, − 0,5, − 1,2 and − 2,4 MPa for three weeks. Generally, effects of salinity and PEG-6000 were similar. Low external osmotic potentials decreased root mass, lowered tissue water potentials, increased stomatal resistance and influenced distribution of Na, K, Ca and Mg in tissues. The similarity of the responses of the plants to salinity and PEG-6000 suggests that the effects of salinity are mediated primarily through low osmotic potentials and not by salinity per se.