Determination of Water Stress of Eucalypts in the Field

Abstract

Two methods for determining plant hydrature in the field have been tested on Eucalyptus viminalis Labill. and E. dalrympleana Maiden one-year-old seedlings. The parameters selected are the physico-chemical properties of sap and the diffusion pressure deficit of leaves. Before extracting sap, leaves have been subjected to two different preliminary treatments to improve permeability of cellular membranes, viz. chloroform and liquid nitrogen treatments, the latter being chosen since it was quicker. Sap has been obtained by espressing at 272 Atm., then filtered and analyzed. Diffusion pressure deficit has been determined by equilibration with vapour. A series of samples has been placed in moist chambers with known water potential until equilibrium has been attained. DPD corresponds to the water potential of the chamber where the sample neither gains nor loses water.