OSMOTIC ADJUSTMENT AND SOLUTE CONSTITUENTS IN LEAVES AND ROOTS OF WATER-STRESSED CHERRY (PRUNUS) TREES

Tissue osmotic potential (PSI-pi) and solute constituents were evaluated in leaves and roots of well-watered and water-stressed Prunus avium L. x pseudocerasus Lindl. 'Colt' and Prunus cerasus L. 'Meteor'. Osmotic potential at full turgor (PSI-pi,sat) decreased in response to water stress for leaves and roots of both cultivars. For 'Colt', a cultivar with an indeterminate growth habit, PSI-pi,sat decreased by 0.56 MPa and 0.38 MPa for terminal expanding leaves and older expanded leaves, respectively. For 'Meteor', a cultivar with a determinate growth habit, PSI-pi,sat decreased by almost-equal-to 0.47 MPa in both terminal and older leaves. Root PSI-pi,sat was alike for both cultivars and showed a similar decrease of 0.20 MPa in response to water stress. Roots had considerably higher PSI-pi,sat than did leaves in both cultivars, irrespective of irrigation treatment. Soluble carbohydrates and potassium (K+) were the major solute constituents in both cultivars. Of the soluble carbohydrates, sorbitol was found in the greatest concentration and accounted for the bulk of water stress-induced solute accumulation in both cultivars. Regardless of the irrigation treatment, mature leaves of 'Meteor' consistently had lower PSI-pi,sat (typically 0.4 MPa) than 'Colt'. This variation in PSI-pi,sat between Prunus cultivars suggests the potential for selection of cultivars with low PSI-pi,sat and possibly superior drought resistance.