Strong thermal acclimation of photosynthesis in tropical and temperate wet‐forest tree species: the importance of altered Rubisco content. (3rd January 2017)

• Record Type: Journal Article
• Authors: Scafaro, Andrew P.; Xiang, Shuang; Long, Benedict M.; Bahar, Nur H. A.; Weerasinghe, Lasantha K.; Creek, Danielle; Evans, John R.; Reich, Peter B.; Atkin, Owen K.
• Is Part Of: Global change biology. Volume 23:Number 7(2017)
• Page Start: 2783
• Page End: 2800
• Publication Date: 2017-01-03
• Subjects: climate modelling -- earth system models -- photosynthesis -- photosynthesis modelling -- Rubisco content -- temperature -- thermal acclimation -- tropical trees -- Vcmax; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.13566
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Understanding of the extent of acclimation of light‐saturated net photosynthesis ( A n ) to temperature ( T ), and associated underlying mechanisms, remains limited. This is a key knowledge gap given the importance of thermal acclimation for plant functioning, both under current and future higher temperatures, limiting the accuracy and realism of Earth system model (ESM) predictions. Given this, we analysed and modelled T ‐dependent changes in photosynthetic capacity in 10 wet‐forest tree species: six from temperate forests and four from tropical forests. Temperate and tropical species were each acclimated to three daytime growth temperatures ( T growth ): temperate – 15, 20 and 25 °C; tropical – 25, 30 and 35 °C. CO2 response curves of A n were used to model maximal rates of RuBP (ribulose‐1, 5‐bisphosphate) carboxylation ( V cmax ) and electron transport ( J max ) at each treatment's respective T growth and at a common measurement T (25 °C). SDS‐PAGE gels were used to determine abundance of the CO2 ‐fixing enzyme, Rubisco. Leaf chlorophyll, nitrogen (N) and mass per unit leaf area (LMA) were also determined. For all species and T growth, A n at current atmospheric CO2 partial pressure was Rubisco‐limited. Across all species, LMA decreased with increasing T growth . Similarly, area‐based rates of V cmax at a measurement T of 25 °C ( V cmax 25 ) linearly declined with increasing T growth, linked to a concomitant decline in total leaf protein per unit leaf area and Rubisco as a percentage of leaf N. The decline in Rubisco constrained V cmax and A n for leaves developed at higher T growth and resulted in poor predictions of photosynthesis by currently widely used models that do not account for T growth ‐mediated changes in Rubisco abundance that underpin the thermal acclimation response of photosynthesis in wet‐forest tree species. A new model is proposed that accounts for the effect of T growth ‐mediated declines in V cmax 25 on A n, complementing current photosynthetic thermal acclimation models that do not account for T sensitivity of V cmax 25 . Abstract : We analysed and modelled temperature‐dependent changes in photosynthetic capacity in 10 wet‐forest tree species; six from temperate forests and four from tropical forests. Area‐based rates of photosynthetic apacity ( V cmax ) linearly declined with increasing growth temperature, linked to a concomitant decline in total leaf protein per unit leaf area and Rubisco as a percentage of leaf nitrogen. A new model is proposed that accounts for the effect of growth temperature‐mediated declines in V cmax on photosynthesis.