PT  - JOURNAL ARTICLE
AU  - Víctor Resco de Dios
AU  - Arthur Gessler
AU  - Juan Pedro Ferrio
AU  - Josu G Alday
AU  - Michael Bahn
AU  - Jorge del Castillo
AU  - Sébastien Devidal
AU  - Sonia García-Muñoz
AU  - Zachary Kayler
AU  - Damien Landais
AU  - Paula Martín-Gómez
AU  - Alexandru Milcu
AU  - Clément Piel
AU  - Karin Pirhofer-Walzl
AU  - Olivier Ravel
AU  - Serajis Salekin
AU  - David T Tissue
AU  - Mark G Tjoelker
AU  - Jordi Voltas
AU  - Jacques Roy
TI  - Does circadian regulation lead to optimal gas exchange regulation?
AID  - 10.1101/121368
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 121368
4099  - http://biorxiv.org/content/early/2017/06/06/121368.short
4100  - http://biorxiv.org/content/early/2017/06/06/121368.full
AB  - Optimal stomatal theory is an evolutionary model proposing that leaves trade-off Carbon (C) for water to maximise C assimilation (A) and minimise transpiration (E), thereby generating a marginal water cost of carbon gain (λ) that remains constant over short temporal scales. The circadian clock is a molecular timer of metabolism that controls A and stomatal conductance (gs), amongst other processes, in a broad array of plant species. Here, we test whether circadian regulation contributes towards achieving optimal stomatal behaviour. We subjected bean (Phaseolus vulgaris) and cotton (Gossypium hirsutum) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature and vapour pressure deficit over 48 hours. We observed a significant and self-sustained circadian oscillation in A and in stomatal conductance (gs) which also led to a circadian oscillation in λ. The lack of constant marginal water cost indicates that circadian regulation does not directly lead to optimal stomatal behaviour. However, the temporal pattern in gas exchange, indicative of either maximizing A or of minimizing E, depending upon time of day, indicates that circadian regulation could contribute towards optimizing stomatal responses. More broadly, our results add to the emerging field of plant circadian ecology and show that molecular controls may partially explain leaf-level patterns observed in the field.