Elevated CO₂ Enhances Dynamic Photosynthesis in Rice and Wheat

Area of Science:

• Plant Physiology
• Crop Science
• Environmental Science

Background:

• Elevated carbon dioxide (eCO2) enhances steady-state leaf photosynthesis in crops.
• Limited understanding exists regarding eCO2's impact on dynamic photosynthesis and its underlying mechanisms.
• Distinguishing between short-term substrate and long-term acclimation effects of eCO2 is crucial.

Purpose of the Study:

• To investigate the effect of eCO2 on dynamic photosynthesis in rice (Oryza sativa japonica) and wheat (Triticum aestivum).
• To quantify the relative contributions of substrate and acclimation effects of eCO2 on photosynthetic responses.
• To assess the impact of eCO2 on accumulative carbon gain during photosynthetic induction.

Main Methods:

• Crops were grown under ambient (400 μmol CO2 mol-1) and elevated (600 μmol CO2 mol-1) CO2 conditions.
• Photosynthetic responses to light fluctuations were measured under different CO2 growth and measurement conditions (Aa, Ae, Ea, Ee).
• Acclimation and substrate effects were quantified by comparing photosynthetic rates and induction states across treatments.

Main Results:

• Elevated CO2 during growth or measurement increased steady-state photosynthetic rates and induction states compared to ambient conditions.
• The substrate effect significantly increased accumulative carbon gain (ACG) during induction (45.5% in rice, 39.3% in wheat).
• The acclimation effect showed varied impacts, decreasing ACG in rice (-18.3%) but increasing it in wheat (7.5%).

Conclusions:

• Elevated CO2 enhances dynamic photosynthetic carbon gain in both rice and wheat, irrespective of whether it occurs during growth or measurement.
• The substrate effect of eCO2 plays a dominant role in increasing carbon gain during photosynthetic induction.
• Future high-CO2 environments may lead to reduced photosynthetic carbon loss due to induction limitations in these crops.