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Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions.

ABSTRACT: BACKGROUND:Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance, and other cell and leaf-level processes over ~24 h under controlled laboratory conditions. The influence of such circadian regulation over whole-canopy fluxes remains uncertain; diurnal CO2 and H2O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other environmental factors. We tested whether circadian regulation would affect plant and canopy gas exchange at the Montpellier European Ecotron. Canopy and leaf-level fluxes were constantly monitored under field-like environmental conditions, and under constant environmental conditions (no variation in temperature, radiation, or other environmental cues). RESULTS:We show direct experimental evidence at canopy scales of the circadian regulation of daytime gas exchange: 20-79 % of the daily variation range in CO2 and H2O fluxes occurred under circadian entrainment in canopies of an annual herb (bean) and of a perennial shrub (cotton). We also observed that considering circadian regulation improved performance by 8-17 % in commonly used stomatal conductance models. CONCLUSIONS:Our results show that circadian controls affect diurnal CO2 and H2O flux patterns in entire canopies in field-like conditions, and its consideration significantly improves model performance. Circadian controls act as a 'memory' of the past conditions experienced by the plant, which synchronizes metabolism across entire plant canopies.

SUBMITTER: Resco de Dios V

PROVIDER: S-EPMC5072338 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions.

Resco de Dios Víctor V Gessler Arthur A Ferrio Juan Pedro JP Alday Josu G JG Bahn Michael M Del Castillo Jorge J Devidal Sébastien S García-Muñoz Sonia S Kayler Zachary Z Landais Damien D Martín-Gómez Paula P Milcu Alexandru A Piel Clément C Pirhofer-Walzl Karin K Ravel Olivier O Salekin Serajis S Tissue David T DT Tjoelker Mark G MG Voltas Jordi J Roy Jacques J

GigaScience 20161020 1

<h4>Background</h4>Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance, and other cell and leaf-level processes over ~24 h under controlled laboratory conditions. The influence of such circadian regulation over whole-canopy fluxes remains uncertain; diurnal CO<sub>2</sub> and H<sub>2</sub>O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other enviro ...[more]

PMID: 27765071

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Project description:BackgroundObtaining instantaneous gas exchanges data is fundamental to gain information on photosynthesis. Leaf level data are reliable, but their scaling up to canopy scale is difficult as they are acquired in standard and/or controlled conditions, while natural environments are extremely dynamic. Responses to dynamic environmental conditions need to be considered, as measurements at steady state and their related models may overestimate total carbon (C) plant uptake.ResultsIn this paper, we describe an automatic, low-cost measuring system composed of 12 open chambers (60 × 60 × 150 cm; around 400 euros per chamber) able to measure instantaneous CO2 and H2O gas exchanges, as well as environmental parameters, at canopy level. We tested the system's performance by simulating different CO2 uptake and respiration levels using a tube filled with soda lime or pure CO2, respectively, and quantified its response time and measurement accuracy. We have been also able to evaluate the delayed response due to the dimension of the chambers, proposing a method to correct the data by taking into account the response time ([Formula: see text]) and the residence time (τ). Finally, we tested the system by growing a commercial soybean variety in fluctuating and non-fluctuating light, showing the system to be fast enough to capture fast dynamic conditions. At the end of the experiment, we compared cumulative fluxes with total plant dry biomass.ConclusionsThe system slightly over-estimated (+ 7.6%) the total C uptake, even though not significantly, confirming its ability in measuring the overall CO2 fluxes at canopy scale. Furthermore, the system resulted to be accurate and stable, allowing to estimate the response time and to determine steady state fluxes from unsteady state measured values. Thanks to the flexibility in the software and to the dimensions of the chambers, even if only tested in dynamic light conditions, the system is thought to be used for several applications and with different plant canopies by mimicking different environmental conditions.

Dataset Information

Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions.

Publications

Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions.

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