Water shortage is one of the most important factors limiting crop yields (Wang et al. 2021), and with the impact of increasing temperatures and changes in precipitation patterns (IPCC 2022), water stress on agriculture is expected to increase with climate change. Plant water resources mainly originate from the soil. Water flow through the soil–plant–atmosphere continuum (SPAC) is driven by transpiration. This water flow is proportional to the gradient in water potentials, where the proportionality factor is given by the hydraulic conductance of the different compartments of the SPAC. When the stomata are open, plant water loss, i.e., the transpiration rate, is set by the evaporative water demand which depends on light, wind, temperature, and relative humidity, and the evaporative surface area over which water can be lost. A large gradient in vapor pressure between the hot and dry air and the moist interior of the leaf, i.e., a high vapor pressure deficit (VPD), will increase the transpiration rate. On the other hand, the transpiration rate is constrained by the ability of the root system to acquire water from the soil and to transport this water to the shoot. This will depend on traits shaping the root system’s water channeling ability.
In this project, we propose to explore the water-centred view outlined by Vadez et al. (2024) to improve crop drought tolerance (here defined as higher yield under water stress and indicated by a high stress tolerance index, STI, Fernandez 1992). It proposes that crop yield tolerance under drought is associated with a balance between conservative and opportunistic water use, which is shaped by traits controlling root water uptake versus shoot water loss by transpiration. In this context, plant hydraulic principles and associated offer a useful, yet understudied, framework for understanding and predicting plant water use patterns under drought. In the HYDROPEARL project, our goal is to gain a deeper mechanistic and genetic understanding of how soil-plant hydraulic mechanisms and traits balance plant water use under atmospheric and soil water limitations.