Mechanisms underlying the resilience of water transport in angiosperm leaves and roots to drought stress

• Applicants: Professor Dr. Mutez Ali Ahmed; Professor Dr. Steven Jansen
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556612650

Climate change represents one of the most important challenges to our planet, resulting in more intense and longer periods of drought at many places worldwide. Drought affects the physiology of many plant species, leading to reduced growth and crop productivity, and contributing to drought-induced forest mortality. Therefore, it is of utmost importance that scientists investigate drought resilience of plants, which includes both the capacity to resist drought and the potential recovery after drought. Plant roots and leaves can be directly exposed to various levels of drought, and are frequently the first organs affected by it. Yet, mechanisms associated with the resistance and potential recovery of these organs remain elusive. We currently do not know how recovery thresholds of roots and leaves relate to each other, and how these are determined by physiological and anatomical traits. Here, we aim to investigate the drought resistance and potential recovery capacity of water transport in roots and leaves to understand at the whole-plant level how angiosperms coordinate the temporal sequence of structural, biochemical, hydraulic, and physiological changes during and after drought. By investigating four angiosperm species (including two herbaceous and two tree species), we will test the overall hypothesis that resistance and recovery thresholds of roots are coordinated with those of leaves. We will also test the mechanisms and functional significance of positive xylem pressure. We hypothesise that stomatal closure is largely driven by a loss in belowground conductivities. We expect that root hair shrinkage and contact loss at the soil-root interface occurs during relatively early stages of drought. We further hypothesise that root cortex and root hair shrinkage as well as recovery thresholds are species and soil textures specific. Once stomata have closed, we hypothesise that stomatal leakiness and cuticular transpiration represent two key traits determining resilience of leaves and drought survival. We also predict that positive xylem pressure contributes to growth and/or tissue rehydration under well hydrated conditions, but it is unclear to what extent this process could be part of a recovery from drought. By bringing together two complementary German research groups, this project raises by far the overall scientific profile of each individual research group, and will make it feasible to combine drought experiments with physiological measurements and various imaging techniques, including X-ray computed tomography. Each key-question will require teamwork bringing together dehydration/rehydration experiments with analyses of anatomical and ecophysiological traits. By linking root and leaf characteristics to drought resistance and recovery, our approach offers a way to better understand the effects of drought stress on herbaceous and woody angiosperm plants.

• DFG Programme: Research Grants