What is ‘drought stress’ and what are options to increase crop yield?

‘Drought’ is vague and ill-defined term that fails to account for the temporal dynamics through the growing seasons due to variable weather conditions, soil water status, plant development stage, and crop growth conditions. These variables all lead to an infinity of responses to water deficit. Instead of the common ‘static’ perspective of drought, it is proposed that a temporally dynamic framework is required within and across growing seasons at a given location. Yield changes in response to trait modification need to be expressed as probabilities obtained from either simulation study or extensive field observations. Such results allow important insight about yield changes that can occur under the economically challenging growing seasons when yields are especially low. Plant traits that result in water conservation early in the growing season in favor of increased availability of water during reproductive development tend to result in high probabilities of yield increase under water-deficit conditions.