Affiliation: | (1) School of Land and Food Sciences, University of Queensland, 4072 St. Lucia, QLD, Australia;(2) Department of Botany, University of Queensland, 4072 St. Lucia, QLD, Australia;(3) Queensland Forestry Research Institute and Cooperative Research Centre for Sustainable Production Forestry, Locked Mail Bag 16, 4570 Gympie, QLD, Australia;(4) Present address: Environmental Protection Agency, Conservation Services Division, QLD Parks and Wildlife Service, Albert Street, P.O. Box 155, 4002, QLD, Australia |
Abstract: | 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% (T100), 70% (T70), 50% (T50) of their water requirements, or were watered only after they were wilted at dawn (T0). Seedlings of E. argophloia had the highest midday net photosynthetic rate (A), stomatal conductance (g s), stomatal density and predawn leaf water potential (pd) in all treatments. The E. cloeziana provenances did not differ in these attributes. The T70 and T50 treatments caused reductions in A of 30% in E. argophloia, and 55% in the E. cloeziana provenances. Under the T0 treatment, E. argophloia maintained higher rates of gas exchange at all levels of water stress than E. cloeziana provenances. The estimates of pd and midday water potential (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 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. |