Mohanned Abdalla1,2, Mutez Ali Ahmed1,3, Gaochao Cai1, Fabian Wankmüller4, Nimrod Schwartz5, Or Litig5, Mathieu Javaux6,7, Andrea Carminati4. 1. Chair of Soil Physics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany. 2. Department of Horticulture, Faculty of Agriculture, University of Khartoum, Khartoum North, Sudan. 3. Department of Land, Air and Water Resources, University of California Davis, Davis, USA. 4. Physics of Soils and Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland. 5. Department of Soil and Water Science, The Hebrew University of Jerusalem, Rehovot, Israel. 6. Earth and Life Institute-Environmental Science, Université catholique de Louvain, Louvain-la-Neuve, Belgium. 7. Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany.
Abstract
BACKGROUND AND AIMS: Stomatal closure allows plants to promptly respond to water shortage. Although the coordination between stomatal regulation, leaf and xylem hydraulics has been extensively investigated, the impact of below-ground hydraulics on stomatal regulation remains unknown. METHODS: We used a novel root pressure chamber to measure, during soil drying, the relation between transpiration rate (E) and leaf xylem water pressure (ψleaf-x) in tomato shoots grafted onto two contrasting rootstocks, a long and a short one. In parallel, we also measured the E(ψleaf-x) relation without pressurization. A soil-plant hydraulic model was used to reproduce the measurements. We hypothesize that (1) stomata close when the E(ψleaf-x) relation becomes non-linear and (2) non-linearity occurs at higher soil water contents and lower transpiration rates in short-rooted plants. KEY RESULTS: The E(ψleaf-x) relation was linear in wet conditions and became non-linear as the soil dried. Changing below-ground traits (i.e. root system) significantly affected the E(ψleaf-x) relation during soil drying. Plants with shorter root systems required larger gradients in soil water pressure to sustain the same transpiration rate and exhibited an earlier non-linearity and stomatal closure. CONCLUSIONS: We conclude that, during soil drying, stomatal regulation is controlled by below-ground hydraulics in a predictable way. The model suggests that the loss of hydraulic conductivity occurred in soil. These results prove that stomatal regulation is intimately tied to root and soil hydraulic conductances.
BACKGROUND AND AIMS: Stomatal closure allows plants to promptly respond to water shortage. Although the coordination between stomatal regulation, leaf and xylem hydraulics has been extensively investigated, the impact of below-ground hydraulics on stomatal regulation remains unknown. METHODS: We used a novel root pressure chamber to measure, during soil drying, the relation between transpiration rate (E) and leaf xylem water pressure (ψleaf-x) in tomato shoots grafted onto two contrasting rootstocks, a long and a short one. In parallel, we also measured the E(ψleaf-x) relation without pressurization. A soil-plant hydraulic model was used to reproduce the measurements. We hypothesize that (1) stomata close when the E(ψleaf-x) relation becomes non-linear and (2) non-linearity occurs at higher soil water contents and lower transpiration rates in short-rooted plants. KEY RESULTS: The E(ψleaf-x) relation was linear in wet conditions and became non-linear as the soil dried. Changing below-ground traits (i.e. root system) significantly affected the E(ψleaf-x) relation during soil drying. Plants with shorter root systems required larger gradients in soil water pressure to sustain the same transpiration rate and exhibited an earlier non-linearity and stomatal closure. CONCLUSIONS: We conclude that, during soil drying, stomatal regulation is controlled by below-ground hydraulics in a predictable way. The model suggests that the loss of hydraulic conductivity occurred in soil. These results prove that stomatal regulation is intimately tied to root and soil hydraulic conductances.
Authors: Rosie A Fisher; Mathew Williams; Raquel Lobo Do Vale; Antonio Lola Da Costa; Patrick Meir Journal: Plant Cell Environ Date: 2006-02 Impact factor: 7.228
Authors: Megan K Bartlett; Tamir Klein; Steven Jansen; Brendan Choat; Lawren Sack Journal: Proc Natl Acad Sci U S A Date: 2016-11-02 Impact factor: 11.205