Elevated [CO₂] raises the temperature optimum of photosynthesis and thus promotes net photosynthesis of winter wheat and rice

Abstract

Atmospheric CO2 concentration ([CO2]) has increased by 49% since the pre‐industrial era, and this increase will continue. Photosynthesis has long been recognized as one of the most temperature‐sensitive processes, while far less is known about how elevated [CO2] (e[CO2]) affect crop photosynthesis response to short‐term temperature increase. To reveal the effect, we measured gas exchange of winter wheat and rice with various leaf temperatures (TL) under different [CO2] conditions (ambient, +120 μmol mol−1 in wheat, +160 μmol mol−1 in rice, and +200 μmol mol−1 in both) using open‐top chamber facility. Analysis of the measurements showed that e[CO2] generally increased net photosynthesis (Pn) by 10–40% across various TL at different developmental stages. The temperature sensitivity of Pn was negatively correlated with TL. Elevated [CO2] raised the temperature optimum (Topt) of Pn by 1.8–5.6°C for wheat and 2.2–4.8°C for rice, resulting in a wider range of TL that can promote Pn. The responses of stomatal conductance, the maximum rate of carboxylation and the ratio of intercellular to growth environment [CO2] to Topt are not only crop‐specific but also stage‐dependent. Furthermore, there is a divergence in the relationships between photosynthetic parameters for wheat and rice at Topt. We conclude that e[CO2] raises Topt of leaf photosynthesis and thus promotes Pn of winter wheat and rice in a humid subtropical climate. Further research on the coordination of leaf hydraulic and photosynthetic parameters in upland wheat and irrigated rice, as well as their response to e[CO2] should be made in the context of climate change.

Regional-scale evaluation of uncertainty in the multi-model simulation of climate change impact on maize and wheat yield

“…Ethiopia is expected to experience a significant increase in warm temperatures, while cold temperatures are anticipated to decrease 30,31 . The negative relationship between net photosynthesis and temperature beyond the optimum temperature affects the final yield 38 . A recent global model intercomparison study projected negative impacts of climate change on wheat in low-latitude regions 4 .…”