Warming alters the positive impact of elevated CO2 concentration on cotton growth and physiology during soil water deficit

Alterations in climate factors such as rising CO 2 concentration ([CO 2]), warming and reduced precipitation may have significant impacts on plant physiology and growth. This research investigated the interactive effects of elevated [CO 2], warming and soil water deficit on biomass production, leaf-level physiological responses and whole-plant water use efficiency (WUEP) in cotton (Gossypium hirsutum L.). Cotton was grown in the glasshouse under two [CO 2] treatments (C A, 400μLL -1; C E, 640μLL -1) and two temperature treatments (T A, 28°C:17°C day:night; T E, 32°C:21°C day:night). Plants were subjected to two progressive water deficit cycles, with a 5-day recovery period between the water deficit periods. C E increased vegetative biomass and photosynthetic rates, and decreased stomatal conductance in T A; however, these responses to C E were not evident under T E. CE increased whole-plant water loss under T A, but increased WUEp, whereas increased whole-plant water loss in T E decreased WUEp regardless of atmospheric [CO 2]. C E may provide some positive growth and physiological benefits to cotton at T A if sufficient water is available but C E will not mitigate the negative effects of rising temperature on cotton growth and physiology in future environments.