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

AbstractMolecular 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 and diurnal CO2and 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 CNRS Ecotron. Canopy and leaf level fluxes were constantly monitored under field-like environmental conditions, and also under constant environmental conditions (no variation in temperature, radiation or other environmental cues). Here we show first direct experimental evidence at canopy scales of circadian gas exchange regulation: 20-79% of the daily variation range in CO2and 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 in commonly used stomatal conductance models. Overall, our results show that overlooked circadian controls affect diurnal patterns of CO2and H2O fluxes in entire canopies and in field-like conditions, although this process is currently unaccounted for in models.

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Does circadian regulation lead to optimal gas exchange regulation?

10.1101/121368 ◽

2017 ◽

Author(s):

Víctor Resco de Dios ◽

Arthur Gessler ◽

Juan Pedro Ferrio ◽

Josu G Alday ◽

Michael Bahn ◽

...

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Vapour Pressure Deficit ◽

Evolutionary Model ◽

Time Of Day ◽

Carbon Gain ◽

Circadian Oscillation ◽

Circadian Regulation ◽

Stomatal Behaviour ◽

Leaf Level

SummaryOptimal 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.

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Growth and grain yield of eight maize hybrids is aligned with water transport, stomatal conductance, and photosynthesis in a semi-arid irrigated system

10.1101/2021.02.04.429760 ◽

2021 ◽

Author(s):

Sean M Gleason ◽

Lauren Nalezny ◽

Cameron Hunter ◽

Robert Bensen ◽

Satya Chintamanani ◽

...

Keyword(s):

Stomatal Conductance ◽

Grain Yield ◽

Water Transport ◽

Co2 Assimilation ◽

Specific Conductance ◽

Soil Conditions ◽

Transport Pathway ◽

Crop Species ◽

Leaf Level ◽

Improved Performance

There is increasing interest in understanding how trait networks can be manipulated to improve the performance of crop species. Working towards this goal, we have identified key traits linking the acquisition of water, the transport of water to the sites of evaporation and photosynthesis, stomatal conductance, and growth across eight maize hybrid lines grown under well-watered and water-limiting conditions in Northern Colorado. Under well-watered conditions, well-performing hybrids exhibited high leaf-specific conductance, low operating water potentials, high rates of midday stomatal conductance, high rates of net CO2 assimilation, greater leaf osmotic adjustment, and higher end-of-season growth and grain yield. This trait network was similar under water-limited conditions with the notable exception that linkages between water transport, midday stomatal conductance, and growth were even stronger than under fully-watered conditions. The results of this experiment suggest that similar trait networks might confer improved performance under contrasting climate and soil conditions, and that efforts to improve the performance of crop species could possibly benefit by considering the water transport pathway within leaves, as well as within the whole-xylem, in addition to root-level and leaf-level traits.

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Circadian Regulation Does Not Optimize Stomatal Behaviour

Plants ◽

10.3390/plants9091091 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1091

Author(s):

Víctor Resco de Dios ◽

William R.L. Anderegg ◽

Ximeng Li ◽

David T. Tissue ◽

Michael Bahn ◽

...

Keyword(s):

Stomatal Conductance ◽

Circadian Variation ◽

Vapour Pressure Deficit ◽

Parameter Estimates ◽

Circadian Regulation ◽

Stomatal Behaviour ◽

Broad Array ◽

Leaf Level ◽

Free Running ◽

Use Efficiency

The circadian clock is a molecular timer of metabolism that affects the diurnal pattern of stomatal conductance (gs), amongst other processes, in a broad array of plant species. The function of circadian gs regulation remains unknown and here, we test whether circadian regulation helps to optimize diurnal variations in stomatal conductance. We subjected bean (Phaseolus vulgaris) and cotton (Gossypium hirsutum) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature, and vapour pressure deficit (free-running conditions) over 48 h. We modelled gs variations in free-running conditions to test for two possible optimizations of stomatal behaviour under circadian regulation: (i) that stomata operate to maintain constant marginal water use efficiency; or (ii) that stomata maximize C net gain minus the costs or risks of hydraulic damage. We observed that both optimization models predicted gs poorly under free-running conditions, indicating that circadian regulation does not directly lead to stomatal optimization. We also demonstrate that failure to account for circadian variation in gs could potentially lead to biased parameter estimates during calibrations of stomatal models. More broadly, our results add to the emerging field of plant circadian ecology, where circadian controls may partially explain leaf-level patterns observed in the field.

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Measurement report: Leaf-scale gas exchange of atmospheric reactive trace species (NO<sub>2</sub>, NO, O<sub>3</sub>) at a northern hardwood forest in Michigan

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-11287-2020 ◽

2020 ◽

Vol 20 (19) ◽

pp. 11287-11304

Author(s):

Wei Wang ◽

Laurens Ganzeveld ◽

Samuel Rossabi ◽

Jacques Hueber ◽

Detlev Helmig

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Tree Species ◽

Leaf Surface ◽

Compensation Point ◽

Trace Gas ◽

Red Maple ◽

White Pine ◽

Canopy Exchange ◽

Leaf Level

Abstract. During the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET) campaign from 21 July to 3 August 2016, field experiments on leaf-level trace gas exchange of nitric oxide (NO), nitrogen dioxide (NO2), and ozone (O3) were conducted for the first time on the native American tree species Pinus strobus (eastern white pine), Acer rubrum (red maple), Populus grandidentata (bigtooth aspen), and Quercus rubra (red oak) in a temperate hardwood forest in Michigan, USA. We measured the leaf-level trace gas exchange rates and investigated the existence of an NO2 compensation point, hypothesized based on a comparison of a previously observed average diurnal cycle of NOx (NO2+NO) concentrations with that simulated using a multi-layer canopy exchange model. Known amounts of trace gases were introduced into a tree branch enclosure and a paired blank reference enclosure. The trace gas concentrations before and after the enclosures were measured, as well as the enclosed leaf area (single-sided) and gas flow rate to obtain the trace gas fluxes with respect to leaf surface. There was no detectable NO uptake for all tree types. The foliar NO2 and O3 uptake largely followed a diurnal cycle, correlating with that of the leaf stomatal conductance. NO2 and O3 fluxes were driven by their concentration gradient from ambient to leaf internal space. The NO2 loss rate at the leaf surface, equivalently the foliar NO2 deposition velocity toward the leaf surface, ranged from 0 to 3.6 mm s−1 for bigtooth aspen and from 0 to 0.76 mm s−1 for red oak, both of which are ∼90 % of the expected values based on the stomatal conductance of water. The deposition velocities for red maple and white pine ranged from 0.3 to 1.6 and from 0.01 to 1.1 mm s−1, respectively, and were lower than predicted from the stomatal conductance, implying a mesophyll resistance to the uptake. Additionally, for white pine, the extrapolated velocity at zero stomatal conductance was 0.4±0.08 mm s−1, indicating a non-stomatal uptake pathway. The NO2 compensation point was ≤60 ppt for all four tree species and indistinguishable from zero at the 95 % confidence level. This agrees with recent reports for several European and California tree species but contradicts some earlier experimental results where the compensation points were found to be on the order of 1 ppb or higher. Given that the sampled tree types represent 80 %–90 % of the total leaf area at this site, these results negate the previously hypothesized important role of a leaf-scale NO2 compensation point. Consequently, to reconcile these findings, further detailed comparisons between the observed and simulated in- and above-canopy NOx concentrations and the leaf- and canopy-scale NOx fluxes, using the multi-layer canopy exchange model with consideration of the leaf-scale NOx deposition velocities as well as stomatal conductances reported here, are recommended.

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Effect of Mycorrhizal Fungi on Gas Exchange of Micropropagated Guava Plantlets (Psidium guajava L.) during Acclimatization and Plant Establishment

HortScience ◽

10.21273/hortsci.33.3.501c ◽

1998 ◽

Vol 33 (3) ◽

pp. 501c-501

Author(s):

Andrés A. Estrada-Luna ◽

Jonathan N. Egilla ◽

Fred T. Davies

Keyword(s):

Tissue Culture ◽

Stomatal Conductance ◽

Gas Exchange ◽

Vapor Pressure ◽

Mycorrhizal Fungi ◽

Vapor Pressure Deficit ◽

Psidium Guajava ◽

Glomus Etunicatum ◽

Plant Establishment ◽

Use Efficiency

The effect of mycorrhizal fungi on gas exchange of micropropagated guava plantlets (Psidium guajava L.) during acclimatization and plant establishment was determined. Guava plantlets (Psidium guajava L. cv. `Media China') were asexually propagated through tissue culture and acclimatized in a glasshouse for eighteen weeks. Half of the plantlets were inoculated with ZAC-19, which is a mixed isolate containing Glomus etunicatum and an unknown Glomus spp. Plantlets were fertilized with modified Long Ashton nutrient solution containing 11 (g P/ml. Gas exchange measurements included photosynthetic rate (A), stomatal conductance (gs), internal CO2 concentration (Ci), transpiration rate (E), water use efficiency (WUE), and vapor pressure deficit (VPD). Measurements were taken at 2, 4, 8 and 18 weeks after inoculation using a LI-6200 portable photosynthesis system (LI-COR Inc. Lincoln, Neb., USA). Two weeks after inoculation, noninoculated plantlets had greater A compared to mycorrhizal plantlets. However, 4 and 8 weeks after inoculation, mycorrhizal plantlets had greater A, gs, Ci and WUE. At the end of the experiment gas exchange was comparable between noninoculated and mycorrhizal plantlets.

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The Effects of Drought on Leaf Gas Exchange and Growth of Three Species of Herbaceous Perennials

HortScience ◽

10.21273/hortsci.33.3.540a ◽

1998 ◽

Vol 33 (3) ◽

pp. 540a-540

Author(s):

K.J. Prevete ◽

R.T. Fernandez

Keyword(s):

Drought Stress ◽

Stomatal Conductance ◽

Gas Exchange ◽

Drought Tolerance ◽

Transpiration Rate ◽

Leaf Gas Exchange ◽

Gas Analysis ◽

Herbaceous Perennials ◽

Effects Of Drought ◽

Analysis System

Three species of herbaceous perennials were tested on their ability to withstand and recover from drought stress periods of 2, 4, and 6 days. Eupatorium rugosum and Boltonia asteroides `Snowbank' were chosen because of their reported drought intolerance, while Rudbeckia triloba was chosen based on its reported drought tolerance. Drought stress began on 19 Sept. 1997. Plants were transplanted into the field the day following the end of each stress period. The effects of drought on transpiration rate, stomatal conductance, and net photosynthetic rate were measured during the stress and throughout recovery using an infrared gas analysis system. Leaf gas exchange measurements were taken through recovery until there were no differences between the stressed plants and the control plants. Transpiration, stomatal conductance, and photosynthesis of Rudbeckia and Boltonia were not affected until 4 days after the start of stress. Transpiration of Eupatorium decreased after 3 days of stress. After rewatering, leaf gas exchange of Boltonia and Rudbeckia returned to non-stressed levels quicker than Eupatorium. Growth measurements were taken every other day during stress, and then weekly following transplanting. Measurements were taken until a killing frost that occurred on 3 Nov. There were no differences in the growth between the stressed and non-stressed plants in any of the species. Plants will be monitored throughout the winter, spring, and summer to determine the effects of drought on overwintering capability and regrowth.

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A reporting format for leaf-level gas exchange data and metadata

Ecological Informatics ◽

10.1016/j.ecoinf.2021.101232 ◽

2021 ◽

Vol 61 ◽

pp. 101232

Author(s):

Kim S. Ely ◽

Alistair Rogers ◽

Deborah A. Agarwal ◽

Elizabeth A. Ainsworth ◽

Loren P. Albert ◽

...

Keyword(s):

Gas Exchange ◽

Leaf Level ◽

Exchange Data

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Normal Cyclic Variation in CO2 Concentration in Indoor Chambers Decreases Leaf Gas Exchange and Plant Growth

Plants ◽

10.3390/plants9050663 ◽

2020 ◽

Vol 9 (5) ◽

pp. 663

Author(s):

James Bunce

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Leaf Gas Exchange ◽

Genetic Material ◽

Co2 Concentration ◽

Cyclic Variation ◽

Indoor Exposure ◽

Elevated Atmospheric Co2 ◽

Gas Exchange System ◽

Opening And Closing

Attempts to identify crop genetic material with larger growth stimulation at projected elevated atmospheric CO2 concentrations are becoming more common. The probability of reductions in photosynthesis and yield caused by short-term variation in CO2 concentration within elevated CO2 treatments in the free-air CO2 enrichment plots raises the question of whether similar effects occur in glasshouse or indoor chamber experiments. These experiments were designed to test whether even the normal, modest, cyclic variation in CO2 concentration typical of indoor exposure systems have persistent impacts on photosynthesis and growth, and to explore mechanisms underlying the responses observed. Wheat, cotton, soybeans, and rice were grown from seed in indoor chambers at a mean CO2 concentration of 560 μmol mol−1, with “triangular” cyclic variation with standard deviations of either 4.5 or 18.0 μmol mol−1 measured with 0.1 s sampling periods with an open path analyzer. Photosynthesis, stomatal conductance, and above ground biomass at 20 to 23 days were reduced in all four species by the larger variation in CO2 concentration. Tests of rates of stomatal opening and closing with step changes in light and CO2, and tests of responses to square-wave cycling of CO2 were also conducted on individual leaves of these and three other species, using a leaf gas exchange system. Reduced stomatal conductance due to larger amplitude cycling of CO2 during growth occurred even in soybeans and rice, which had equal rates of opening and closing in response to step changes in CO2. The gas exchange results further indicated that reduced mean stomatal conductance was not the only cause of reduced photosynthesis in variable CO2 conditions.

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Ozone damage, detoxification and the role of isoprenoids – new impetus for integrated models

Functional Plant Biology ◽

10.1071/fp15302 ◽

2016 ◽

Vol 43 (4) ◽

pp. 324 ◽

Cited By ~ 15

Author(s):

Supriya Tiwari ◽

Rüdiger Grote ◽

Galina Churkina ◽

Tim Butler

Keyword(s):

Stomatal Conductance ◽

Environmental Conditions ◽

Economic Losses ◽

Plant Responses ◽

Damage Scenarios ◽

Biochemical Processes ◽

Wide Range ◽

Defence Responses ◽

High Concentrations ◽

The Impact

High concentrations of ozone (O3) can have significant impacts on the health and productivity of agricultural and forest ecosystems, leading to significant economic losses. In order to estimate this impact under a wide range of environmental conditions, the mechanisms of O3 impacts on physiological and biochemical processes have been intensively investigated. This includes the impact on stomatal conductance, the formation of reactive oxygen species and their effects on enzymes and membranes, as well as several induced and constitutive defence responses. This review summarises these processes, discusses their importance for O3 damage scenarios and assesses to which degree this knowledge is currently used in ecosystem models which are applied for impact analyses. We found that even in highly sophisticated models, feedbacks affecting regulation, detoxification capacity and vulnerability are generally not considered. This implies that O3 inflicted alterations in carbon and water balances cannot be sufficiently well described to cover immediate plant responses under changing environmental conditions. Therefore, we suggest conceptual models that link the depicted feedbacks to available process-based descriptions of stomatal conductance, photosynthesis and isoprenoid formation, particularly the linkage to isoprenoid models opens up new options for describing biosphere-atmosphere interactions.

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Boron Supply and Water Deficit Consequences in Young ParicÃ¡ (Schizolobium parahyba var. amazonicum) Plants

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha44110136 ◽

2016 ◽

Vol 44 (1) ◽

pp. 250-256 ◽

Cited By ~ 1

Author(s):

Bianca do Carmo SILVA ◽

PÃªola Reis de SOUZA ◽

Daihany Moraes CALLEGARI ◽

Vanessa Ferreira ALVES ◽

Allan Klynger da Silva LOBATO ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Stomatal Conductance ◽

Gas Exchange ◽

Water Use Efficiency ◽

Water Deficit ◽

Water Use ◽

Electrolyte Leakage ◽

Tolerance Mechanism ◽

Schizolobium Parahyba ◽

Use Efficiency

Boron (B) is a very important nutrient required by forest plants; when supplied in adequate amounts, plants can ameliorate the negative effects of abiotic stresses. The objective of this study was to (i) investigate gas exchange, (ii) measure oxidant and antioxidant compounds, and (iii) respond how B supply acts on tolerance mechanism to water deficit in young Schizolobium parahyba plants. The experiment employed a factorial that was entirely randomised, with two boron levels (25 and 250 Âµmol L-1, simulating conditions of sufficient B and high B, respectively) and two water conditions (control and water deficit). Water deficit induced negative modifications on net photosynthetic rate, stomatal conductance and water use efficiency, while B high promoted intensification of the effects on stomatal conductance and water use efficiency. Hydrogen peroxide and electrolyte leakage of both tissues suffered non-significant increases after B high and when applied water deficit. Ascorbate levels presented increases after water deficit and B high to leaf and root. Our results suggested that the tolerance mechanism to water deficit in young Schizolobium parahyba plants is coupled to increases in total glutathione and ascorbate aiming to control the overproduction of hydrogen peroxide and alleviates the negative consequences on electrolyte leakage and gas exchange. In relation to B supply, this study proved that sufficient level promoted better responses under control and water deficit conditions.

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