Drought Resistance, Water Potential and Water Content in some New Zealand Plants

Abstract

Summary The drought resistance of cut shoots and leaves of some 23 (mostly native) woody plants and ferns, showed a gradation from species that were resistant to water loss but damaged by relatively small water deficits (drought avoiders) to those that lost water readily but were damaged only by large water deficits (drought t oler at ors). Drought avoidance tended to be associated with low symplastic water content at the turgor loss point, large amounts of “bound” water and small changes in water potential with water content beyond the turgor loss point; whereas drought tolerance was associated with opposite values of the same parameters. Bulk moduli of elasticity were not significantly associated with drought resistance but were positively correlated with the water content at zero turgor. Species with low ratios of saturated water content to dry weight tend to have low solute water potentials, low relative water contents at zero turgor and show a steep decline of water potential with decreasing water content. Neither drought avoidance nor tolerance were particularly associated with any morphological or taxonomic grouping or with field observations of drought resistance, although there was some tendency for conifers to be drought avoiders and for species that are widespread in dry sites to be tolerators rather than avoiders.