This title appears in the Scientific Report : 2014 

Modelling the impact of heterogeneous rootzone water distribution on the regulation of transpiration by hormone transport and/or hydraulic pressures
Huber, Katrin (Corresponding Author)
Vanderborght, Jan / Javaux, Mathieu / Schröder, Natalie / Dodd, Ian C. / Vereecken, Harry
Agrosphäre; IBG-3
Plant and soil, 384 (2014) 1-2, S. 93-112
Dordrecht [u.a.] Springer Science + Business Media B.V 2014
10.1007/s11104-014-2188-4
Journal Article
Terrestrial Systems: From Observation to Prediction
Modelling and Monitoring Terrestrial Systems: Methods and Technologies
Please use the identifier: http://dx.doi.org/10.1007/s11104-014-2188-4 in citations.
Aims: A simulation model to demonstrate that soil water potential can regulate transpiration, by influencing leaf water potential and/or inducing root production of chemical signals that are transported to the leaves.Methods: Signalling impacts on the relationship between soil water potential and transpiration were simulated by coupling a 3D model for water flow in soil, into and through roots (Javaux et al.2008) with a model for xylem transport of chemicals (produced as a function of local root water potential). Stomatal conductance was regulated by simulated leaf water potential (H) and/or foliar chemical signal concentrations (C; H+C). Split-root experiments were simulated by varying transpiration demands and irrigation placement.Results: While regulation of stomatal conductance by chemical transport was unstable and oscillatory, simulated transpiration over time and root water uptake from the two soil compartments were similar for both H and H+C regulation. Increased stomatal sensitivity more strongly decreased transpiration, and decreased threshold root water potential (below which a chemical signal is produced) delayed transpiration reduction. Conclusions: Although simulations with H+C regulation qualitatively reproduced transpiration of plants exposed to partial rootzone drying (PRD), long-term effects seemed negligible. Moreover, most transpiration responses to PRD could be explained by hydraulic signalling alone.