Simulating transpiration and leaf water relations in response to heterogeneous soil moisture and different stomatal control mechanisms

Abstract

Aims Stomata can close to avoid cavitation under decreased soil water availability. This closure can be triggered by hydraulic ('H') and/or chemical signals ('C', 'H + C'). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive direct relations that link soil water availability, expressed as fraction of roots in dry soil (f dry ), to transpiration reduction. Methods We used the mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontal and vertical splits with varying f dry and different strengths of stomatal regulation by chemical and hydraulic signals. Results Transpiration reduction predicted by the direct relations was in good agreement with numerical simulations. For small enough potential transpiration and large enough root hydraulic conductivity and stomatal sensitivity to chemical signalling isohydric plant behaviour originates from H + C control whereas anisohydric behaviour emerges from C control. For C control the relation between transpiration reduction and f dry becomes independent of transpiration rate whereas H + C control results in stronger reduction for higher transpiration rates. Conclusion Direct relations that link effective soil water potential and leaf water potential can describe different stomatal control resulting in contrasting behaviour.

Grapevine adaptations to water stress: new perspectives about soil/plant interactions

“…The delayed interruption of the signal, much more gradual than the initial release, suggests a further role of the hormone on the embolisms repair (Lovisolo et al 2008a). The relative importance of the chemical signalling compared to the hydraulic balance in the plant response to water stress remains a debated issue (Chaves et al 2010;Tombesi et al 2015) also investigated through numerical models (Huber et al 2014(Huber et al , 2015.…”

“…Root embolization is thought to limit water use by the plant and be protective against the propagation of low xylem tension to the stem. Its importance over chemical signalling for stomatal regulation have been suggested by modelling studies showing that most transpiration responses to PRD treatments could be interpreted by hydraulic signalling alone, and that regulation of stomatal conductance by chemical transport was unstable and oscillatory (Huber et al (2014(Huber et al ( , 2015). …”

Isotopic approaches to quantifying root water uptake and redistribution: a review and comparison of methods

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MARSHAL, a novel tool for virtual phenotyping of maize root system hydraulic architectures

“…FSRSM are potentially useful instruments for virtual breeding as they allow one to investigate the behavior of any desired combination of plant traits within any environmental condition, including contrasted pedo-climatic scenarios (Chapman 2007). They also allow one to highlight mechanisms, regulation rules and feedbacks that are expected to influence plant transpiration (Huber et al 2015) and yield (Meunier et al 2016; Srinivasan, Kumar, and Long 2016). In addition, FSRSM enable crossing scales and to predict the impact of deterministic relations, observed and valid on short timescales, on the overall relations within a system in specific pedo-climatic conditions (Hammer et al 2009).…”