JXB Advance Access published online on March 13, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp021
RESEARCH PAPER |
Influence of leaf dry mass per area, CO2, and irradiance on mesophyll conductance in sclerophylls
1School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia
2School of Biomedical, Biomolecular and Chemical Sciences, Faculty of Life and Physical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia
3Agricultural Landscapes, CSIRO Sustainable Ecosystems, Floreat, WA 6014, Australia
4Environmental Biology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia
* To whom correspondence should be addressed: foteini{at}cyllene.uwa.edu.au
Leaf photosynthesis (A) is limited by mesophyll conductance (gm), which is influenced by both leaf structure and the environment. Previous studies have indicated that the upper bound for gm declines as leaf dry mass per area (LMA, an indicator of leaf structure) increases, extrapolating to zero at a LMA of about 240 g m–2. No data exist on gm and its response to the environment for species with LMA values higher than 220 g m–2. In this study, laboratory measurements of leaf gas exchange and in vivo chlorophyll a fluorescence were used concurrently to derive estimates of gm in seven species of the Australian sclerophyllous genus Banksia covering a wide range of LMA (130–480 g m–2). Irradiance and CO2 were varied during those measurements to gauge the extent of environmental effects on gm. A significant decrease of gm with increasing LMA was found. gm declined by 35–60% in response to increasing atmospheric CO2 concentrations at high irradiance, with a more variable response (0–60%) observed at low irradiance, where gm was, on average, 22% lower than at high irradiance at ambient CO2 concentrations. Despite considerable variation in A and LMA between the Banksia species, the CO2 concentrations in the intercellular air spaces (Ci, 262±5 µmol mol–1) and in the chloroplasts (Cc, 127±4 µmol mol–1) were remarkably stable.
Key words: Banksia, CO2, leaf anatomy, leaf internal conductance, light intensity, photosynthesis, sclerophylly
Received 19 November 2008; Revised 14 January 2009 Accepted 16 January 2009
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