Key message Heat stress (HS) under well-watered conditions was not detrimental to leaf photosynthesis or yield but modified the elevated CO 2 response of photosynthesis and yield in two contrasting wheat cultivars. Abstract Climate change is increasing the frequency of extreme events such as heat waves, adversely affecting crop productivity. While positive impacts of elevated carbon dioxide (eCO 2 ) on crop productivity are ev...

Cyclic electron flow (CEF) around photosystem I (PSI) is essential for generating additional ATP and enhancing efficient photosynthesis. Accurate estimation of CEF requires knowledge of the fractions of absorbed light by PSI ( f I ) and PSII ( f II ), which are only known for a few model species such as spinach. No measures of f I are available for C 4 grasses under different irradiances. We developed a new method to estimate...

Rising atmospheric CO 2 concentrations is expected to stimulate photosynthesis and carbohydrate production, while inhibiting photorespiration. By contrast, nitrogen (N) concentrations in leaves generally tend to decline under elevated CO 2 (eCO 2 ), which may reduce the magnitude of photosynthetic enhancement. We tested two hypotheses as to why leaf N is reduced under eCO 2 : (a) A “dilution effect” caused by increased concent...

Climate is an important factor limiting tree distributions and adaptation to different thermal environments may influence how tree populations respond to climate warming. Given the current rate of warming, it has been hypothesized that tree populations in warmer, more thermally stable climates may have limited capacity to respond physiologically to warming compared to populations from cooler, more seasonal climates. We determi...

Elevated atmospheric CO 2 ( eCO 2 ) is expected to reduce the impacts of drought and increase photosynthetic rates via two key mechanisms: first, through decreased stomatal conductance (g s ) and increased soil water content ( V SWC ) and second, through increased leaf internal CO 2 (C i ) and decreased stomatal limitations (S lim ). It is unclear if such findings from temperate grassland studies similarly pertain to warmer ec...

Impacts of climate warming depend on the degree to which plants are constrained by adaptation to their climate‐of‐origin or exhibit broad climatic suitability. We grew cool‐origin, central and warm‐origin provenances of Eucalyptus tereticornis in an array of common temperature environments from 18 to 35.5°C to determine if this widely distributed tree species consists of geographically contrasting provenances with differentiat...

As rapid climate warming creates a mismatch between forest trees and their home environment, the ability of trees to cope with warming depends on their capacity to physiologically adjust to higher temperatures. In widespread species, individual trees in cooler home climates are hypothesized to more successfully acclimate to warming than their counterparts in warmer climates that may approach thermal limits. We tested this pred...

To investigate if Eucalyptus species have responded to industrial‐age climate change, and how they may respond to a future climate, we measured growth and physiology of fast‐ ( E. saligna ) and slow‐growing ( E. sideroxylon ) seedlings exposed to preindustrial (290), current (400) or projected (650 μL L −1 ) CO 2 concentration ([CO 2 ]) and to current or projected (current +4 °C) temperature. To evaluate maximum potential trea...