The scarcity of water resources in semiarid regions forces scientists to find alternative cultivation techniques which can help to maintain a more sustainable / economically viable agriculture. Deficit irrigation strategies, which supply only a proportion of the crop¿s water requirements, are a potential irrigation management to optimise water resources.

To efficiently use these irrigation techniques to improve crop water use efficiency, it is necessary to improve our understanding of the physiological processes by which plants respond to reduced water availability.

Stomatal Closure and Its Role in Plant Survival

Stomatal closure is a primary response to water deficit resulting in reduced transpiration and water loss, thereby contributing to plant survival during periods of drought, and therefore represents an important target for improving plant responses to reduced water availability. Although both hydraulic and chemical signals are involved in stomatal responses to reduced water availability, there remain several controversies in the literature.

Recent results of our group have found that plants of Pelargonium x hortorum regulates the intensity of hydraulic and ABA signalling in response to regular re-watering under chronic water deficit. Stomatal closure is associated with decreased leaf water potential only under rapid soil drying when water is withheld.

Proposed Research: Determining Physiological Mechanisms and Crop Water Use Efficiency

This proposed research aims to determine the physiological mechanisms by which long-distance signalling is attenuated by sustained deficit irrigation, and whether this improves crop water use efficiency. To achieve this global objective, several experiments will be carried out in plants grown in a controlled environment greenhouse. Plants will be subject to different irrigation treatments; a rapid, acute water deficit and a long term, chronic water deficit (sustained deficit irrigation; SDI, 50% of crop evapotranspiration). Throughout each experiment, soil water content, root and leaf water potential, stomatal conductance, photosynthesis, xylem ABA and ACC concentrations, foliar ethylene production and gene expression will be measured. By determining the mechanisms(s) by which sustained deficit irrigation attenuates ABA signalling, we will optimize the application of deficit irrigation strategies to improve leaf-level and crop water use efficiency.