Through stimulation of root growth, increasing atmospheric CO 2 concentration ([CO 2 ]) may facilitate access of crops to sub-soil water, which could potentially prolong physiological activity in dryland environments, particularly because crops are more water use efficient under elevated [CO 2 ] (e[CO 2 ]). This study investigated the effect of drought in shallow soil versus sub-soil on agronomic and physiological responses of wheat to e[CO 2 ] in a glasshouse experiment.
