1. The instantaneous and integrated leaf gas exchange of 13 species of southern hemisphere conifers grown under identical glasshouse conditions were examined to determine whether there was any correlation between the characteristics of water use at the leaf level and environmental water availability. 2. In the conifer species examined, the minimum ratio of internal to ambient CO2 measured in leaves during artificially imposed drought [(C(i)/C(a))(min)] was strongly correlated with the minimum rainfall observed within the natural range of each species. This suggests that the distributions of these species are constrained by the drought tolerance of their photosynthetic apparatus. 3. A good correlation was found between the ratio of internal to ambient CO2 measured in leaves under optimal conditions (C(i)/C(a))(max) and leaf δ13C (and hence inferred ∫ [C(i)/C(a)]). Neither of these, however, correlated with the environmental parameters considered most likely to be limiting species distribution, i.e. precipitation and altitude. 4. These data suggest that decreasing water availability may have been the major factor responsible for the restriction and extinction of conifers in the southern hemisphere.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the environmental sciences
UTAS Author:	Brodribb, TJ (Professor Tim Brodribb)
UTAS Author:	Hill, RS (Professor Bob Hill)
ID Code:	14955
Year Published:	1998
Web of Science® Times Cited:	79
Deposited By:	Plant Science
Deposited On:	1998-08-01
Last Modified:	2011-08-09
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