Salt tolerance in Suaeda maritima (l.) dum. fine structure and ion concentrations in the apical region of roots

Anatomy and ion concentrations have been studied in the roots of the halophyte Suaeda maritima (L.)Dum. growing in saline and non-saline conditions. The roots were fine with only three layers of cortical cells. Salinization of the growth medium resulted in cellular vacuolation commencing closer to the apex than in non-salinized plants and led to an increase in root dimensions through increased cell (vacuole) size but not increased cell numbers: the Casparian strip developed much closer to the apex and was twice as long in salt-grown plants. Ion concentrations were determined in sections (1 mm) of root. The apical 1 mm was predominantly non-vacuolate, with a K+ concentration greater than 100 mol m-3 and a Na: K ratio less than 2, even when growing in 340 mol m-3 NaCl. The adaptive value of the anatomical observations are discussed and the ion concentration data assessed in relation to current concepts of the haiophyte cell.