Does circadian regulation lead to optimal gas exchange regulation?

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

10.1101/054593 ◽

2016 ◽

Author(s):

Víctor Resco de Dios ◽

Arthur Gessler ◽

Juan Pedro Ferrio ◽

Josu G Alday ◽

Michael Bahn ◽

...

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Environmental Conditions ◽

Circadian Regulation ◽

Molecular Clocks ◽

Flux Dynamics ◽

Vapor Flux ◽

Leaf Level ◽

Improved Performance ◽

Temperature Radiation

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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Gas exchanges and photosynthetic efficiency in sub-forest species from Atlantic Forest

Research Society and Development ◽

10.33448/rsd-v9i5.2870 ◽

2020 ◽

Vol 9 (5) ◽

pp. e43952870

Author(s):

Magnólia Martins Alves ◽

Manoel Bandeira de Albuquerque ◽

Renata Ranielly Pedroza Cruz ◽

Mário Luiz Farias Cavalcanti

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Water Use ◽

Co2 Concentration ◽

Time Of Day ◽

Forest Understory ◽

Forest Species ◽

Gas Exchanges ◽

Endogenous Factors ◽

Intrinsic Efficiency

The availability of light is one of the factors that most limits the photosynthesis of juvenile trees in the understory of the forest. The study was carried out in the Mata do Pau-Ferro State Park, located in the city of Areia, PB. The objective of this study was to evaluate how gas exchanges occur in individuals of Psychotria colorata (Willd. Ex Roem & Schult.), Senna georgica Irwin & Barneby, Himatanthus phagedaenicus (Mart.) Woodson, Solanum swartzianum Roem. & Schult, Psychotria carthagenensis Jacq.e Psychotria hoffmannseggiana (Willd. ex Schult.) in the understory of a remnant of Mata Atlântica. The rate of photosynthesis (A), transpiration (E), stomatal conductance (Gs), internal CO2 concentration (Ci) leaf temperature-air temperature (°C), and internal carbon (Ci), instantaneous efficiency of water use (EUA) (A/E), Intrinsic efficiency of water use (EiUC) (A/Gs) and the intrinsic efficiency of carboxylation (ratio A/Ci). The rates of maximum photosynthesis (A), photosynthesis (E) and stomatal conductance (Gs) were shown to be influenced by the time of day, as there was no interference of external factors in the diurnal patterns of gas exchange, variations are due to endogenous factors, probably due to the circadian rhythm. The parameter of the gas exchange of sub-forest species responds differently, in the small variations in the luminosity levels of the forest understory

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GAS EXCHANGE, GROWTH, YIELD AND BEVERAGE QUALITY OF COFFEA ARABICA CULTIVARS GRAFTED ON TO C. CANEPHORA AND C. CONGENSIS

Experimental Agriculture ◽

10.1017/s0014479701002010 ◽

2001 ◽

Vol 37 (2) ◽

pp. 241-252 ◽

Cited By ~ 19

Author(s):

J. I. FAHL ◽

M. L. C. CARELLI ◽

H. C. MENEZES ◽

P. B. GALLO ◽

P. C. O. TRIVELIN

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Carbon Isotope ◽

Coffea Arabica ◽

Carbon Isotope Discrimination ◽

Growth Yield ◽

Carbon Gain ◽

Dry Period ◽

Isotope Discrimination

Gas exchange, leaf carbon isotope discrimination, growth, yield and beverage quality were evaluated for two Coffea arabica cultivars (Catuai and Mundo Novo), grafted on to C. canephora and C. congensis progenies growing in open fields. During the years 1994 to 1997, grafting resulted in an average increase in bean yield of 151 and 89% for Catuai and Mundo Novo respectively. As analysed by sensory analyses and by the ratio between the mono-isomers and di-isomers of caffeoylquinic acid, beverage quality of the C. arabica was not altered by grafting. Shoot growth was significantly greater in grafted plants, showing an increase of 52% in total leaf area compared with the non-grafted plants. Under conditions of water excess in the soil there was little difference in the transpiration and stomatal conductance rates between the grafted and non-grafted plants, but the net photosynthesis was higher in grafted plants. With an accentuated water deficit in the soil in the dry period, the grafted plants showed significantly higher transpiration and stomatal conductance rates than the non-grafted plants, and similar values to those of C. canephora. Carbon isotope discrimination was greater in the grafted plants, suggesting greater root hydraulic conductance. The results suggest that the better performance of the grafted plants during the dry period was due to the greater capacity of the root system of C. canephora to provide water to the shoot thereby maintaining greater gas exchange in the leaves and consequently a greater carbon gain.

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Simultaneous Effects of Foliar Nitrogen, Temperature, and Humidity on Gas Exchange in Pinus radiata

Functional Plant Biology ◽

10.1071/pp9950615 ◽

1995 ◽

Vol 22 (4) ◽

pp. 615 ◽

Cited By ~ 6

Author(s):

DW Sheriff ◽

JP Mattay

Keyword(s):

Gas Exchange ◽

Pinus Radiata ◽

Vapour Pressure ◽

Measurement Data ◽

Carbon Assimilation ◽

Vapour Pressure Deficit ◽

Leaf Temperature ◽

Carbon Gain ◽

Foliar Nitrogen ◽

Foliar N

Seedlings of Pinus radiata were grown in a glasshouse in large pots with sand as the potting mix. They were kept well-watered and frequently supplied with nutrient solutions which contained different amounts of nitrogen for different treatments. Carbon assimilation and diffusive conductance of the foliage were measured under steady-state conditions at saturating light in all treatments. Experimental variables were leaf-air vapour pressure difference and leaf temperature at time of measurement. Data were fitted to a non-linear regression equation to examine responses of carbon assimilation, diffusive conductance, transpiration, assimilatory nitrogen-use efficiency, and assimilatory transpiration efficiency to foliar nitrogen concentration expressed on a leaf area basis ([N]), to leaf temperature, and to leaf-air vapour pressure (D). Parameters from the regression have been used to plot three-dimensional surfaces, so that simultaneous effects of experimental variables can be easily visualised. Carbon assimilation increased linearly with foliar [N], declined exponentially as D increased, and had a broad temperature optimum between c. 14 and 38�C. Diffusive conductance increased linearly with foliar [N], was related to the reciprocal of D, and declined as temperature increased. Using climatic vapour pressure deficit and air temperature data for Canberra, ACT, and for Mount Gambier, SA, and with the functions that had been fitted to experimental data, it was found that these regional climatic differences have potential for appreciably affecting carbon gain and water loss in the regions, which have P. radiata plantations. Predicted differences in carbon gain are of the order of reported differences in stem growth in the regions. This shows the need to take into account regional variation in climatic variables that strongly affect gas exchange when investigating regional differences in productivity.

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CARBON GAIN IN COFFEA ARABICA DURING CLEAR AND CLOUDY DAYS IN THE WET SEASON

Experimental Agriculture ◽

10.1017/s0014479705003121 ◽

2006 ◽

Vol 42 (2) ◽

pp. 147-164 ◽

Cited By ~ 15

Author(s):

J. C. RONQUIM ◽

C. H. B. A. PRADO ◽

P. NOVAES ◽

J. I. FAHL ◽

C. C. RONQUIM

Keyword(s):

Gas Exchange ◽

Coffea Arabica ◽

Leaf Gas Exchange ◽

Photochemical Efficiency ◽

Vapour Pressure Deficit ◽

Net Photosynthesis ◽

Photon Flux ◽

Photon Flux Density ◽

Carbon Gain ◽

Wet Season

Three cultivars of Coffea arabica, Catuaí Vermelho IAC 81, Icatu Amarelo IAC 2944 and Obatã IAC 1669–20, were evaluated in relation to leaf gas exchange and potential photochemical efficiency of photosystem II under field conditions on clear and cloudy days in the wet season in southeast Brazil. Independent of levels of irradiance, leaf water potential (υleaf) values were always higher than the minimum required to affect daily net photosynthesis (PN). PN, stomatal conductance (gs), leaf transpiration (E) and the index of photochemical efficiency (Fv/Fm) declined on a clear day in all cultivars. The depression of leaf gas exchange and Fv/Fm (specially around midday) caused a strong decrease (about 70 %) in daily carbon gain on a clear day. Under cloudless conditions, gs and PN were correlated with the air vapour pressure deficit (VPDair), but not with photosynthetic photon flux density (PPFD) values. On a cloudy day, the daily carbon gain was barely limited by PPFD below 800 μmol m−2 s−1, the Fv/Fm values showed a slight decrease around midday, and gs and PN were positively correlated with PPFD but not with VPDair. By contrast, irrespective of the contrasting irradiance conditions during the day, PN and E were correlated with gs.

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Ozone Amplifies Water Loss from Mature Trees in the Short Term But Decreases It in the Long Term

Forests ◽

10.3390/f11010046 ◽

2019 ◽

Vol 11 (1) ◽

pp. 46

Author(s):

Elena Paoletti ◽

Nancy E. Grulke ◽

Rainer Matyssek

Keyword(s):

Steady State ◽

Stomatal Conductance ◽

Gas Exchange ◽

Water Loss ◽

Vapour Pressure Deficit ◽

Environmental Parameters ◽

Mechanistic Explanation ◽

Short Term ◽

Mature Trees

We measured whole-tree transpiration of mature Fagus sylvatica and Picea abies trees exposed to ambient and twice-ambient O3 regimes (1xO3 and 2xO3 free-air fumigation). After eight years, mean daily total transpiration did not vary with the O3 regime over the 31 days of our study, even though individual daily values increased with increasing daily O3 peaks in both species. Although the environmental parameters were similar at 1xO3 and 2xO3, the main factors affecting daily transpiration were vapour pressure deficit in 2xO3 spruce and O3 peaks in beech. For a mechanistic explanation, we measured O3-induced sluggish stomatal responses to variable light (sunflecks) by means of leaf-level gas exchange measurements only in the species where O3 was a significant factor for transpiration, i.e., beech. Stomata were always slower in closing than in opening. The 2xO3 stomata were slower in opening and mostly in closing than 1xO3 stomata, so that O3 uptake and water loss were amplified before a steady state was reached. Such delay in the stomatal reaction suggests caution when assessing stomatal conductance under O3 pollution, because recording gas exchange at the time photosynthesis reached an equilibrium resulted in a significant overestimation of stomatal conductance when stomata were closing (ab. 90% at 1xO3 and 250% at 2xO3). Sun and shade leaves showed similar sluggish responses, thus suggesting that sluggishness may occur within the entire crown. The fact that total transpiration was similar at 1xO3 and 2xO3, however, suggests that the higher water loss due to stomatal sluggishness was offset by lower steady-state stomatal conductance at 2xO3. In conclusion, O3 exposure amplified short-term water loss from mature beech trees by slowing stomatal dynamics, while decreased long-term water loss because of lower steady-state stomatal conductance. Over the short term of this experiment, the two responses offset each other and no effect on total transpiration was observed.

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Ecophysiological Responses of desert shrub to rainfall addition for Reaumurica soongorica in desert ecosystem

10.5194/egusphere-egu2020-5176 ◽

2020 ◽

Author(s):

Wei Li ◽

Cicheng Zhang

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Leaf Gas Exchange ◽

Vapour Pressure Deficit ◽

Desert Ecosystem ◽

Heihe River ◽

Desert Ecosystems ◽

Rainfall Events ◽

Ecophysiological Responses ◽

Predominant Factor

Desert environments are characterized by limited and highly variable rainfall, which is an intermittent source of water critical to the evolution of the structure and functioning of desert ecosystems. The present study was to assess the effects of different amounts of rainfall received through discrete rainfall events and of the ecophysiological responses for Reaumurica soongorica along multiple average precipitation (MAP) gradient. A field experiment was performed under seven simulated rainfall amounts (0 - 40 mm) with Reaumurica soongorica at respective High-P (120 mm), Middle-P (67 mm), and Low-P (35 mm) sites along middle and lower reach of Heihe River Basin in July, 2015. Pre-dawn plant water potential (&#968;pd), the rates of photosynthesis and stomatal conductance were measured synchronously. Results showed that: photosynthetic response of R.soongorica to rainfall pulse was significant different. The mean daily leaf gas exchange and maximum photosynthesis rate (Pn-max) of R.soongorica were decreased obviously with decreasing MAP. Vapour pressure deficit (VPD) was the predominant factor for gas exchange limiting. Under the control of VPD, stomatal conductance was pregressively reduced with decreasing &#968;pd, which was functioned as limiting Pn-max and further increasing water use efficiency (WUE). However, when MAP was declined below 35 mm, the response of stomatal conductance to &#968;pd was weakened, from which Pn-max began to increase again. 2 to 4 days hystereric response of R.soongorica &#968;pd to various rainfall events was found in High-P. Stomatal conductance was then increased linearly with increasing &#968;pd, from which Pn-max was also enhanced linearly. While weakly response of &#968;pd to similar rainfall events was observed in Low-P, where stomatal conductance and Pn-max was maintained stable after rain. Mentioned above, the effective rainfall pluse, induced by obvious physiological response of R. soongorica, was 3.63-6.73 mm and 6.73-10.09 mm for Linze and Ejina, respective. Our results provided comprehensively understanding in the consequences of long-term variability in rainfall for the physiology of desert plants and species dynamics in desert ecosystems.

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Irrigated Shiraz vines (Vitis vinifera) upregulate gas exchange and maintain berry growth in response to short spells of high maximum temperature in the field

Functional Plant Biology ◽

10.1071/fp09101 ◽

2009 ◽

Vol 36 (9) ◽

pp. 801 ◽

Cited By ~ 48

Author(s):

Chris J. Soar ◽

Marisa J. Collins ◽

Victor O. Sadras

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Vitis Vinifera ◽

Fruit Set ◽

Sugar Content ◽

Vapour Pressure Deficit ◽

Maximum Temperature ◽

Sugar Accumulation ◽

Short Period ◽

High Maximum

We tested the hypotheses that (i) a short period of high maximum temperature disrupts gas exchange and arrests berry growth and sugar accumulation in irrigated Shiraz vines (Vitis vinifera L.), and (ii) the magnitude of these effects depend on the phenological window when stress occur. Using a system combining passive heating (greenhouse effect) and active cooling (fans) to control daytime temperature, we compared vines heated to a nominal maximum of 40°C for three consecutive days and untreated controls. Maximum air temperature in heated treatments was 7.3°C (2006–07) and 6.5°C (2007–08) above ambient. Heat episodes were aligned with the beginning of a weekly irrigation cycle and applied in one of four phenological windows, namely post-fruit set, pre-veraison, veraison and pre-harvest. Heating systems did not affect relative humidity, hence vapour pressure deficit (VPD) was increased in the heated treatments and tracked the daily cycle of temperature. Heat did not affect the dynamics of berry growth and sugar accumulation, except for a 16% reduction in berry size and sugar content in vines heated shortly after fruit set in 2006–07. Vines upregulated stomatal conductance and gas exchange in response to heat. Stomatal conductance, photosynthesis and transpiration at a common VPD were consistently higher in heated vines than in controls. We suggest that stomatal behaviour previously described as part of Shiraz anisohydric syndrome may be adaptive in terms of heat tolerance at the expense of short-term transpiration efficiency.

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Factors influencing the measurement of assimilation and stomatal conductance with the LI-COR 6400XT gas exchange system.

10.1101/494120 ◽

2018 ◽

Author(s):

Daniel LeCain ◽

Sean Gleason

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Experimental Error ◽

Leaf Age ◽

Time Of Day ◽

Species Variation ◽

Plant Responses ◽

Exchange System ◽

Leaf Chamber ◽

Gas Exchange System

Abstract: Although CO2 and H2O exchange rates are often measured in experiments as indicators of physiological plant responses these gas exchange measurements are prone to large experimental error. Gas exchange equipment and technology have improved greatly over the past two decades which supports scrutinizing current issues of experimental error in measuring plant photosynthesis and stomatal conductance. This report shows results of a greenhouse experiment with the goal of identifying lessor understood sources of experimental error and variation in measurements with the LI-COR 6400XT gas exchange system. A variety of plant types were used to encompass differing species variation. We found significant sources of experimental error in 1) the time for initial adjustment when placing a leaf in the leaf chamber 2) the time-of-day when measuring 3) leaf age 4) having the chamber window full vs. partially full with leaf tissue 5) using a leaf chamber environment that greatly diverges from the whole plant environment 6) differing degree of experimental error depending upon plant species. A situation with multiple contributors to error would result in useless gas-exchange data. Recommendations for minimizing these experimental errors are given.

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