Root signalling and osmotic adjustment during intermittent soil drying sustain grain yield of field grown wheat |
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| Institution: | 1. The Royal Veterinary and Agricultural University, Department of Agricultural Sciences, Laboratory for Agrohydrology and Bioclimatology, Agrovej 10, DK-2630, Taastrup, Denmark;2. Research Centre Foulum, Danish Institut for Plant and Soil Science, P.O. Box 25, DK-8830, Tjele, Denmark;3. 21 Hurrell Road, Cambridge, CB4 3 RQ, UK;1. Control Systems Group, Technische Universität Berlin, Germany;2. Sensorimotor Performance Lab, University of Konstanz, Germany;3. Kocaeli University, Kocaeli, Turkey;4. Neurological University Clinics, Freiburg, Germany;1. Laboratoire de Reproduction et Développement des Plantes, Université Claude Bernard Lyon 1, Ecole Normale Supérieure de Lyon, Institut National de la Recherche Agronomique (INRA) Centre National de la Recherche Scientifique (CNRS), Lyon, France;2. Virtual Plants INRIA Team, Unité Mixte de Recherche (UMR) Amélioration Génétique et Adaptation des Plantes (AGAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche en Informatique et en Automatique (INRIA), INRA, Montpellier, France;1. Murmansk Marine Biological Institute of Russian Academy of Sciences, Vladimirskaya str., 17, Murmansk 183010, Russia;2. Murmansk Arctic State University, Kapitana Egorova str., 15, Murmansk 183038, Russia |
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| Abstract: | A field study was conducted to investigate the effect of intermittent soil drying on resulting non-hydraulic and hydraulic root signals, leaf gas exchange, leaf growth, day of heading, leaf osmotic adjustment and yield of wheat grown in sand and loam soils in lysimeters. A 40-day-drought treatment was imposed when the flag leaf started to emerge and was terminated close to maturity. Soil water content and soil water potential of various soil layers were measured using the neutron moderation method and tensiometers, respectively. Soil drying in the top soil layers induced increase in both xylem and bulk-leaf abscisic acid (ABA) content and reduced the stomatal conductance and leaf growth even before a measurable change in leaf water potential could be detected in droughted plants when compared with fully watered plants. Further, heading and flowering occurred 4 days earlier in the droughted than in the well-watered plants before any loss in leaf water potential had occurred as compared with the fully watered plants. When more severe drought reduced the leaf water status, further accumulation of leaf ABA occurred and transpiration decreased in addition to gradual osmotic adjustment and senescence of older leaves. The osmotic adjustment sustained leaf turgor pressure during soil drying. At severe drought, the osmotic adjustment at full turgor in the flag leaves was 0.85 MPa. In sand, the kernel dry weight increased and as a result similar grain yield was obtained in both the treatments. In loam which had more water available than sand, no significant reduction in the final yield was induced by the drought. It is concluded that (1) non-hydraulic root signals caused early drought adaptation at mild water stress by reducing leaf growth and stomatal conductance and hastening of heading and flowering; (2) osmotic adjustment sustained turgor maintenance and hence the yield-forming processes during moderate and severe water stress. |
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