Photosynthesis–nitrogen relationships in tropical forest tree species as affected by soil phosphorus availability: a controlled environment study
Keith J. Bloomfield A B E , Graham D. Farquhar B and Jon Lloyd C D
+ Author Affiliations
- Author Affiliations
A School of Geography, University of Leeds, Leeds LS2 9JT, UK.
B Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
C Grand Challenges in Ecosystems and the Environment Initiative, Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, Berkshire, UK.
D Centre for Tropical Environmental and Sustainability Science and School of Marine and Tropical Biology, James Cook University, Cairns, Qld 4878, Australia.
E Corresponding author. Email: keith.bloomfield@anu.edu.au
Functional Plant Biology 41(8) 820-832 https://doi.org/10.1071/FP13278
Submitted: 20 September 2013 Accepted: 17 February 2014 Published: 4 April 2014
Abstract
Tropical soils are often characterised by low phosphorus availability and tropical forest trees typically exhibit lower area-based rates of photosynthesis (Aa) for a given area-based leaf nitrogen concentration ([N]a) compared with plants growing in higher-latitude, N-limited ecosystems. Nevertheless, to date, very few studies have assessed the effects of P deprivation per se on Aa ↔ [N]a relationships in tropical trees. Our study investigated the effect of reduced soil P availability on light-saturated Aa and related leaf traits of seven Australian tropical tree species. We addressed the following questions: (1) Do contrasting species exhibit inherent differences in nutrient partitioning and morphology? (2) Does P deprivation lead to a change in the nature of the Aa ↔ [N]a relationship? (3) Does P deprivation lead to an alteration in leaf nitrogen levels or N allocation within the leaf? Applying a mixed effects model, we found that for these Australian tropical tree species, removal of P from the nutrient solution decreased area-based photosynthetic capacity (Amax,a) by 18% and reduced the slope of the Amax,a ↔ [N]a relationship and differences among species accounted for around 30% of response variation. Despite greater N allocation to chlorophyll, photosynthetic N use efficiency was significantly reduced in low-P plants. Collectively, our results support the view that low soil P availability can alter photosynthesis–nitrogen relationships in tropical trees.
Additional keywords: carboxylation capacity, leaf nutrient partitioning, leaf trait relationships, phosphorus deprivation, ribulose biphosphate regeneration.
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