Keith J Bloomfield1, Graham D Farquhar2, Jon Lloyd3. 1. School of Geography, University of Leeds, Leeds LS2 9JT, UK. 2. Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia. 3. 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.
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.
Tropical soils are often characterised by low phosphorus availability anpan>d tropical forest trees typically exhibit lower area-based rates of photosynthesis (Aa) for a given area-based leaf pan> class="Chemical">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.
Authors: Franklin Magnum de Oliveira Silva; Rafaela Gageti Bulgarelli; Umarah Mubeen; Camila Caldana; Sara Adrian L Andrade; Paulo Mazzafera Journal: Front Plant Sci Date: 2022-09-15 Impact factor: 6.627