Xylem Permeability and Embolism Susceptibility in Seedlings of Eucalyptus camaldulensis Dehnh. From Two Different Climatic Zones

Abstract

We examined the hydraulic architecture of Eucalyptus camaldulensis seedlings from two climatically different provenances: Petford in north Queensland, which is humid; and Tennant Creek in the Northern Territory, which is semi-arid. Xylem liquid specific permeability (Kg) was calculated from measurements of xylem air permeability (K_g) and hydraulic resistances (R) were also calculated. Embolism susceptibility curves were constructed by measuring K_g in the stems of young seedlings. Canopy leaf areas were mapped and sap flows through the Tennant Creek and Petford seedlings were simulated. Results showed that the permeability of stem wood in the Tennant Creek seedling was about 40% higher than in Petford, and the permeability of its branch wood was about 25% higher. The threshold water potential for initiation of embolisms (Ψt) was slightly lower in Tennant Creek seedlings (- 3.3 MPa compared with - 3.0 MPa) and the number of embolisms with decreasing Ψ was lower for Tennant Creek seedlings. Sap flow simulations showed differences in the distribution of water throughout the seedling canopies. The results are discussed in terms of the ecology of the two eucalypt provenances.