Differences in drought responses of three contrasting Eucalyptus microtheca F.!Muell. populations

Changes in dry matter accumulation and allocation, leaf stomatal properties and some aspects of leaf water relations of three contrasting Eucalyptus microtheca F. Muell. populations were recorded after exposure to drought stress. The populations used were from West Kimberleys (northwestern Australia), Central Australia and Walgett (southeastern Australia). In the controlled environment study there were three watering regimes which were watered to 100, 50 and 25% field capacity, respectively. Significant differences in dry matter accumulation and allocation, leaf guard cell length, the minimum daily leaf water potential, carbon isotope composition (described as water-use efficiency) and abscisic acid (ABA) concentration were detected among populations. Compared with the southeastern population, under water deficit the northwestern and central populations had lower biomass production and higher root/shoot ratio, foliage area/stem cross-sectional area ratio and specific leaf area density. The northwestern and central populations also exhibited higher minimum daily water potentials, water-use efficiencies and ABA accumulation as effected by drought than the southeastern population. These morphological and physiological responses to water availability showed that the different populations may employ different survival strategies under drought stress at the initial phase of seedling growth and establishment. The southeastern population possesses a prodigal water-use strategy and quick growth, while the northwestern and central populations exhibit conservative water-use strategies and slow growth. These differences in drought responses maybe used as criteria for genotype selection in and and semi-arid regions. (C) 2002 Elsevier Science B.V. All rights reserved.