Leveraging Diversity in Environmental Driven Responses Reveals a Key Role for Mesophyll Conductance and Root Sink Strength Under Elevated CO 2 and Temperature

In future climates both CO 2 and temperature are predicted to rise. Using high‐throughput phenotyping, the diversity of 31 different banana varieties and their associated traits were leveraged to understand the impact of potential future climatic conditions of combined elevated CO 2 (e[CO 2 ]) and temperature. Under ambient CO 2 (a[CO 2 ]) the adaxial/abaxial stomatal density ratio (rSD) was identified as a strong predictor of growth, but its importance diminished when CO 2 was highly abundant. When evaluated at 400 versus 800 ppm and 30°C versus 34°C, variation in mesophyll conductance (g m ) and root sink strength drove growth under both a[CO 2 ] and e[CO 2 ]. Significant positive correlations between the e[CO 2 ] response of stomatal conductance (g s,c ), transpiration (E), root to shoot ratio, net photosynthetic rate at saturating irradiance (A sat ), maximum rate of electron transport (J max ) and maximum triose phosphate utilisation rate (TPU max ) indicated a coupling between sink strength, photosynthetic capacity and stomatal regulation. Moreover, g m and g s,c concurrently reduced under e[CO 2 ]. Interactions between acclimation towards e[CO 2 ] and temperature were evident on gas exchange and photosynthetic capacity. Under the investigated conditions, e[CO 2 ] counteracted the negative effect of the supra‐optimal temperature on growth. Varieties with high mesophyll conductance and root sink strength benefitted most from e[CO 2 ] driven growth and photosynthesis enhancement. Results were further validated in an ecotron facility. This study reveals rSD, g m and root sink strength as potential traits for crop improvement and highlights the importance of evaluating the simultaneous impact of CO 2 and temperature in future climate studies.