Interactions of elevated [CO2] and night temperature on rice growth and yield

To understand how a combination of high night temperature and elevated [CO2] during the reproductive growth period affects rice growth and yield, we conducted a pot experiment in four controlled-environment chambers with two levels of [CO2] (ambient, 380 ppm; and elevated, 680 ppm) and two levels of night temperature (22 and 32 °C). The day temperature was 32 °C in all treatments. As results, the whole plant and stem dry weight were significantly increased by both elevated [CO2] and high night temperature (P < 0.01), while the ear dry weight was significantly increased by elevated [CO2] and decreased by high night temperature (both P < 0.01). The fertilized spikelet number was significantly decreased by high night temperature (P < 0.01), but not affected by elevated [CO2] (P = 0.18). The individual grain weight was significantly increased by elevated [CO2] (P = 0.03). Consequently, brown rice yield was significantly increased by elevated [CO2] (P < 0.01) but decreased by high night temperature (P < 0.01), with a significant interaction of [CO2] and night temperature (P < 0.05). The results indicate that high night temperature will reduce the stimulatory effect of elevated [CO2] on rice production in the future if both continue to increase.