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Photosynthesis within isobilateral Eucalyptus pauciflora leaves.
John R Evans1, Thomas C Vogelmann
1Environmental Biology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia. evans@rsbs.anu.edu.au
The New Phytologist
|August 22, 2006
Summary
Eucalyptus pauciflora leaves exhibit distinct photosynthetic capacity profiles, peaking near the surfaces and decreasing centrally. Vertical leaf orientation optimizes photosynthesis when light is unilateral.
Area of Science:
- Plant Physiology
- Photosynthesis Research
- Eucalyptus Biology
Background:
- Adult Eucalyptus pauciflora leaves display vertical orientation.
- Leaves possess multiple palisade cell layers and oil glands.
Purpose of the Study:
- Characterize light absorption, chlorophyll, photosynthetic capacity, and CO2 fixation profiles in Eucalyptus pauciflora leaves.
- Investigate the impact of leaf orientation on photosynthesis.
Main Methods:
- Chlorophyll fluorescence imaging of leaf cross-sections under varying light directions.
- 14CO2 labeling combined with paradermal cryosectioning to map photosynthesis.
- Multilayer model using Beer's law for 14C fixation profile prediction.
Main Results:
- Photosynthetic capacity peaked 75 micrometers beneath each leaf surface, lowest in the center.
- A multilayer model accurately predicted 14C fixation profiles.
- Vertically acclimated leaves gained 79% of daily photosynthesis when horizontal but outperformed horizontal leaves when vertical.
- Photosynthetic capacity profiles correlated with light absorption profiles under unilateral illumination.
Conclusions:
- Leaf structure influences photosynthetic capacity distribution.
- Vertical leaf orientation is advantageous under unilateral light conditions.
- Gas exchange measurements under unilateral light may underestimate true photosynthetic capacity.