Interactive effects of elevated CO2 concentration and combined heat and drought stress on tomato photosynthesis

Abstract Background Extreme weather events are predicted to increase, such as combined heat and drought. The CO 2 concentration ([CO 2 ]) is predicted to approximately double by 2100. We aim to explore how tomato physiology, especially photosynthesis, is affected by combined heat and drought under elevated [CO 2 ] (e [CO 2 ]). Results Two genotypes, ‘OuBei’ (‘OB’, Solanum lycopersicum ) and ‘LA2093’ ( S. pimpinellifolium ) were grown at a [CO 2 ] (atmospheric [CO 2 ], 400 ppm) and e [CO 2 ] (800 ppm), respectively. The 27-days-old seedlings were treated at 1) a [CO 2 ], 2) a [CO 2 ] + combined stress, 3) e [CO 2 ] and 4) e [CO 2 ] + combined stress, followed by recovery. The P N (net photosynthetic rate) increased at e [CO 2 ] as compared with a [CO 2 ] and combined stress inhibited the P N . Combined stress decreased the F v /F m (maximum quantum efficiency of photosystem II) of ‘OB’ at e [CO 2 ] and that of ‘LA2093’ in regardless of [CO 2 ]. Genotypic difference was observed in the e [CO 2 ] effect on the gas exchange, carbohydrate accumulation, pigment content and dry matter accumulation. Conclusions Short-term combined stress caused reversible damage on tomato while the e [CO 2 ] alleviated the damage on photosynthesis. However, the e [CO 2 ] cannot be always assumed have positive effects on plant growth during stress due to increased water consumption. This study provided insights into the physiological effects of e [CO 2 ] on tomato growth under combined stress and contributed to tomato breeding and management under climate change.