Physiological responses to water stress in Eucalyptus cloeziana and E. argophloia seedlings

• Published in: Trees (Berlin, West) West), 2004-07, Vol.18 (4), p.381-389
• Main Authors: Ngugi, M.R, Doley, D, Hunt, M.A, Ryan, P, Dart, P
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; drought; Drought resistance; drought tolerance; duration; Economic plant physiology; Eucalyptus; Eucalyptus argophloia; Eucalyptus cloeziana; forest plantations; forest trees; Fundamental and applied biological sciences. Psychology; Gas exchange; geographical variation; Humid climates; leaf water potential; Leaves; photosynthesis; Physiological responses; Seedlings; Stomatal conductance; Stress; tree physiology; Water potential; Water relations, transpiration, stomata; Water requirements; Water stress
• ISSN: 0931-1890; 1432-2285
• DOI: 10.1007/s00468-003-0316-5

Effects of water stress duration and intensity on gas exchange and leaf water potential were investigated in 7-month-old seedlings of a humid coastal provenance (Gympie) and a dry inland (Hungry Hills) provenance of E. cloeziana F. Muell. and in a dry inland (Chinchilla) provenance of E. argophloia Blakely supplied with 100% (T^sub 100^), 70% (T^sub 70^), 50% (T^sub 50^) of their water requirements, or were watered only after they were wilted at dawn (T^sub 0^). Seedlings of E. argophloia had the highest midday net photosynthetic rate (A), stomatal conductance (g ^sub s^), stomatal density and predawn leaf water potential (Ψ^sub pd^) in all treatments. The E. cloeziana provenances did not differ in these attributes. The T^sub 70^ and T^sub 50^treatments caused reductions in A of 30% in E. argophloia, and 55% in the E. cloeziana provenances. Under the T^sub 0^ treatment, E. argophloia maintained higher rates of gas exchange at all levels of water stress than E. cloeziana provenances. The estimates of Ψ^sub pd^ and midday water potential (Ψ^sub md^) at which plants remained wilted overnight were respectively: -2.7 and -4.1 MPa for E. cloeziana (humid), -2.8 and -4.0 MPa for E. cloeziana (dry) and, -3.7 and -4.9 MPa for E. argophloia. Following stress relief, both A and g ^sub s^ recovered more quickly in E. argophloia and in the dry provenance of E. cloeziana than in the humid provenance. We conclude that E. argophloia is more drought tolerant and has a potential for cultivation in the humid and semi humid climates, whilst E. cloeziana has greater potential in the humid subtropical climates.[PUBLICATION ABSTRACT]