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Abstract Photosynthetic acclimation to both warming and elevated CO2of boreal trees remains a key uncertainty in modelling the response of photosynthesis to future climates. We investigated the impact of increased growth temperature and elevated CO2on photosynthetic capacity (VcmaxandJmax) in mature trees of two North American boreal conifers, tamarack and black spruce. We show thatVcmaxandJmaxat a standard temperature of 25°C did not change with warming, whileVcmaxandJmaxat their thermal optima (Topt) and growth temperature (Tg) increased. Moreover,VcmaxandJmaxat either 25°C,ToptorTgdecreased with elevated CO2. TheJmax/Vcmaxratio decreased with warming when assessed at bothToptandTgbut did not significantly vary at 25°C. TheJmax/Vcmaxincreased with elevated CO2at either reference temperature. We found no significant interaction between warming and elevated CO2on all traits. If this lack of interaction between warming and elevated CO2on theVcmax,JmaxandJmax/Vcmaxratio is a general trend, it would have significant implications for improving photosynthesis representation in vegetation models. However, future research is required to investigate the widespread nature of this response in a larger number of species and biomes.
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Using the rapid A‐C i response (RACiR) in the Li‐Cor 6400 to measure developmental gradients of photosynthetic capacity in poplar
Abstract The rapid A‐Ciresponse (RACiR) technique alleviates limitations of measuring photosynthetic capacity by reducing the time needed to determine the maximum carboxylation rate (Vcmax) and electron transport rate (Jmax) in leaves. Photosynthetic capacity and its relationships with leaf development are important for understanding ecological and agricultural productivity; however, our current understanding is incomplete. Here, we show that RACiR can be used in previous generation gas exchange systems (i.e., the LI‐6400) and apply this method to rapidly investigate developmental gradients of photosynthetic capacity in poplar. We compared RACiR‐determined Vcmaxand Jmaxas well as respiration and stomatal conductance (gs) across four stages of leaf expansion inPopulus deltoidesand the poplar hybrid 717‐1B4 (Populus tremula × Populus alba). These physiological data were paired with leaf traits including nitrogen concentration, chlorophyll concentrations, and specific leaf area. Several traits displayed developmental trends that differed between the poplar species, demonstrating the utility of RACiR approaches to rapidly generate accurate measures of photosynthetic capacity. By using both new and old machines, we have shown how more investigators will be able to incorporate measurements of important photosynthetic traits in future studies and further our understanding of relationships between development and leaf‐level physiology.
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- Award ID(s):
- 1301346
- PAR ID:
- 10078470
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Plant, Cell & Environment
- Volume:
- 42
- Issue:
- 2
- ISSN:
- 0140-7791
- Page Range / eLocation ID:
- p. 740-750
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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