Phosphorus recycling in photorespiration maintains high photosynthetic capacity in woody species |
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Authors: | DAVID S ELLSWORTH KRISTINE Y CROUS HANS LAMBERS JULIA COOKE |
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Institution: | 1. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, New South Wales, Australia;2. School of Plant Biology, The University of Western Australia, Perth, Western Australia, Australia;3. Department of Biological Sciences, Faculty of Science, Macquarie University, North Ryde, New South Wales, Australia |
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Abstract: | Leaf photosynthetic CO2 responses can provide insight into how major nutrients, such as phosphorus (P), constrain leaf CO2 assimilation rates (Anet). However, triose‐phosphate limitations are rarely employed in the classic photosynthesis model and it is uncertain as to what extent these limitations occur in field situations. In contrast to predictions from biochemical theory of photosynthesis, we found consistent evidence in the field of lower Anet in high CO2] and low O2] than at ambient O2]. For 10 species of trees and shrubs across a range of soil P availability in Australia, none of them showed a positive response of Anet at saturating CO2] (i.e. Amax) to 2 kPa O2. Three species showed >20% reductions in Amax in low O2], a phenomenon potentially explained by orthophosphate (Pi) savings during photorespiration. These species, with largest photosynthetic capacity and Pi > 2 mmol P m?2, rely the most on additional Pi made available from photorespiration rather than species growing in P‐impoverished soils. The results suggest that rarely used adjustments to a biochemical photosynthesis model are useful for predicting Amax and give insight into the biochemical limitations of photosynthesis rates at a range of leaf P concentrations. Phosphate limitations to photosynthetic capacity are likely more common in the field than previously considered. |
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Keywords: | low oxygen concentration nitrogen phosphorus phosphate limitations photosynthesis: carbon reactions sclerophyll trees |
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