Leaf hydraulic properties are strongly linked with transpiration and photosynthesis in many species, but it is not known if gas exchange and hydraulics will have co-ordinated responses to climate change. Locke et al. study soybean (Glycine max) and find that leaf hydraulic conductance (Kleaf) does not change for plants grown at elevated [CO2] or elevated temperature, despite changes in photosynthesis and stomatal conductance. This lack of coordination between Kleaf and gas exchange in response to growth environment is observed in both field- and chamber-grown soybeans. Such an imbalance could lead to hydraulic limitation of photosynthesis under extreme environmental conditions.