Evaluating kinetic fractionation factors used for reconstructions from oxgen and hydrogen isotope ratios in plant water and cellulose

Buhay, William M.; Edwards, Thomas W. D.; Aravena, Ramón

doi:10.1016/0016-7037(96)00073-7

Cited by 54 publications

(41 citation statements)

References 46 publications

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“…It has been suggested that most of the discrepancies between modeled and measured leaf water isotopic compositions could be resolved by careful estimation of the kinetic fractionation factor, ⑀ k (Buhay et al, 1996). As expected from Equation 2, ⑀ k and consequently ⌬ C are sensitive to the boundary layer conductance to water vapor diffusion (g b ), especially at the lower range of g b (Fig.…”

Section: Applying the String-of-lakes Model To Leaves For ⌬ 18 O Leafmentioning

confidence: 98%

“…An alternative method to calculate ⑀ k is described by Buhay et al (1996), taking leaf size and morphology into consideration. To explain the observation that bulk leaf water is less enriched than that predicted by the CraigGordon model, Leaney et al (1985) described leaf water as consisting of two pools: evaporatively enriched leaf tissue water and isotopically unaltered vascular water (Fig.…”

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confidence: 99%

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18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

et al. 2002

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Three leaf water models (two-pool model, Péclet effect, and string-of-lakes) were assessed for their robustness in predicting leaf water enrichment and its spatial heterogeneity. This was achieved by studying the 18 O spatial patterns of vein xylem water, leaf water, and dry matter in cotton (Gossypium hirsutum) leaves grown at different humidities using new experimental approaches. Vein xylem water was collected from intact transpiring cotton leaves by pressurizing the roots in a pressure chamber, whereas the isotopic content of leaf water was determined without extracting it from fresh leaves with the aid of a purpose-designed leaf punch. Our results indicate that veins have a significant degree of lateral exchange with highly enriched leaf water. Vein xylem water is thus slightly, but progressively enriched in the direction of water flow. Leaf water enrichment is dependent on the relative distances from major veins, with water from the marginal and intercostal regions more enriched and that next to veins and near the leaf base more depleted than the Craig-Gordon modeled enrichment of water at the sites of evaporation. The spatial pattern of leaf water enrichment varies with humidity, as expected from the string-of-lakes model. This pattern is also reflected in leaf dry matter. All three models are realistic, but none could fully account for all of the facets of leaf water enrichment. Our findings acknowledge the presence of capacitance in the ground tissues of vein ribs and highlight the essential need to incorporate Péclet effects into the string-of-lakes model when applying it to leaves.The isotopic composition of leaf water reflects local humidity, and its imprints on plant cellulose and other fossil materials have been widely explored for palaeoclimatic reconstruction. To date, isotopic values of wood cellulose (Epstein et al., 1977;Yapp and Epstein, 1982;Edwards et al., 1985;Edwards and Fritz, 1986;Roden et al., 2000), grassland phytoliths (Webb and Longstaffe, 2000), and deer bone (Cormie et al., 1994) have been shown to be related to leaf water isotopic composition. Leaf water isotopic signature is not only imprinted on plant organic matter but is also recorded in atmospheric CO 2 and O 2 . The CO 2 interacts and undergoes isotopic exchange with leaf water, and O 2 is released by the plant during photosynthesis. Changes in the oxygen isotope ratios of CO 2 and O 2 can thus be used to study variations in the net exchange of CO 2 in terrestrial ecosystems and in the balance of terrestrial and marine productivity (Bender et al., 1985;Bender et al., 1994). Because all of these applications critically depend on estimation of the leaf water oxygen isotopic ratio, a good understanding of the nature of leaf water enrichment is needed.The isotopic composition of leaf water is most commonly estimated from the model of a freely evaporating water surface (Craig and Gordon, 1965) where isotopic fractionation is driven by the lower vapor pressure and diffusivity of the heavier molecules. Although the Craig-Gordon m...

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Section: Applying the String-of-lakes Model To Leaves For ⌬ 18 O Leafmentioning

confidence: 98%

mentioning

confidence: 99%

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

et al. 2002

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“…The average value of λ LW−IW (0.519) is close to the value of θ diff calculated for the diffusion of vapor in air (0.518; Barkan and Luz, 2007). As schematically described in Landais et al (2016), λ transp (equivalent to λ LW−IW ) represents the interplay among three processes in the leaf boundary layer: (1) the equilibrium fractionation, which is only temperaturedependent (Majoube, 1971) and drives the isotope composition of leaf water along the equilibrium water line (θ equil = 0.529); (2) the diffusion transport leading to increasing kinetic fractionation with decreasing relative humidity along the diffusion line; (3) the isotope exchange of leaf water with atmospheric water vapor, decreasing from turbulent to laminar and molecular leaf boundary layer vapor transport conditions (e.g., Buhay et al, 1996). In the case of the growth chamber experiment, the fact that λ LW−IW is close to θ diff supports that the increasing diffusion of vapor in air when RH decreases or transpiration increases is the main process controlling the evolution of 17 O-excess LW .…”

Section: Irrigation and Soil Watersmentioning

confidence: 99%

“…The δ 18 O LW is commonly modelled as a function of the isotope composition of absorbed water, the isotope composition of water vapor, and RH (Craig and Gordon, 1965). The Craig and Gordon simple approach overestimates δ 18 O LW and different corrections have been proposed to take into account the diffusion of the evaporating water back to the leaf lamina and the advection of less evaporated stem water (i.e., the Péclet effect, Buhay et al, 1996;Helliker and Ehleringer, 2000;Roden et al, 2000;Farquhar and Gan, 2003;Farquhar and Cernusak, 2005;Ripullone et al, 2008;Treydte et al, 2014). In the growth chamber experiment, where water availability, relative humidity, and temperature were kept constant, we assume that transpiration rapidly reached a steady state and that the isotope composition of transpired water was the same as that of the irrigation water entering the plant (e.g., Welp et al, 2008 (2000) proposed, for monocotyledonous species characterized by a vertical parallel veinal structure, to use instead of the Craig and Gordon model the Gat and Bowser (1991) Table S3 was either higher or lower than the observed 17 O-excess e LW−IW .…”

Section: Irrigation and Soil Watersmentioning

confidence: 99%

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

et al. 2018

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Abstract. Continental atmospheric relative humidity (RH) is a key climate parameter. Combined with atmospheric temperature, it allows us to estimate the concentration of atmospheric water vapor, which is one of the main components of the global water cycle and the most important gas contributing to the natural greenhouse effect. However, there is a lack of proxies suitable for reconstructing, in a quantitative way, past changes of continental atmospheric humidity. This reduces the possibility of making model-data comparisons necessary for the implementation of climate models. Over the past 10 years, analytical developments have enabled a few laboratories to reach sufficient precision for measuring the triple oxygen isotopes, expressed by the 17 O-excess ( 17 O-excess = ln (δ 17 O + 1) -0.528 × ln (δ 18 O + 1)), in water, water vapor and minerals. The 17 O-excess represents an alternative to deuterium-excess for investigating relative humidity conditions that prevail during water evaporation. Phytoliths are micrometric amorphous silica particles that form continuously in living plants. Phytolith morphological assemblages from soils and sediments are commonly used as past vegetation and hydrous stress indicators. In the present study, we examine whether changes in atmospheric RH imprint the 17 O-excess of phytoliths in a measurable way and whether this imprint offers a potential for reconstructing past RH. For that purpose, we first monitored the 17 O-excess evolution of soil water, grass leaf water and grass phytoliths in response to changes in RH (from 40 to 100 %) in a growth chamber experiment where transpiration reached a steady state. Decreasing RH from 80 to 40 % decreases the 17 Oexcess of phytoliths by 4.1 per meg/% as a result of kinetic fractionation of the leaf water subject to evaporation. In order to model with accuracy the triple oxygen isotope fractionation in play in plant water and in phytoliths we recommend direct and continuous measurements of the triple isotope composition of water vapor. Then, we measured the 17 O-excess of 57 phytolith assemblages collected from top soils along a RH and vegetation transect in inter-tropical West and Central Africa. Although scattered, the 17 O-excess of phytoliths decreases with RH by 3.4 per meg/%. The similarity of the trends observed in the growth chamber and nature supports that RH is an important control of 17 O-excess of phytoliths in the natural environment. However, other parameters such as changes in the triple isotope composition of the soil water or phytolith origin in the plant may come into play. Assessment of these parameters through additional growth chambers experiments and field campaigns will bring us closer to an accurate proxy of changes in relative humidity.

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“…The term e k was calculated using equations from Appendix C of Buhay, Edwards & Aravena (1996), accounting for dissected leaf morphology, and incorporating on-site measurements of mean late-morning wind speed. The kinetic fractionation factor used was the revised value for oxygen isotopomers of water from Cappa et al (2003).…”

Section: Assessing the Péclet Effectmentioning

confidence: 99%

Needle cell elongation and maturation timing derived from pine needle cellulose δ¹⁸O

Wright

Leavitt

2005

Plant Cell & Environment

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Evaluating kinetic fractionation factors used for reconstructions from oxgen and hydrogen isotope ratios in plant water and cellulose

Cited by 54 publications

References 46 publications

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

Needle cell elongation and maturation timing derived from pine needle cellulose δ¹⁸O

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Evaluating kinetic fractionation factors used for reconstructions from oxgen and hydrogen isotope ratios in plant water and cellulose

Cited by 54 publications

References 46 publications

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

The triple oxygen isotope composition of phytoliths as a proxy of continental atmospheric humidity: insights from climate chamber and climate transect calibrations

Needle cell elongation and maturation timing derived from pine needle cellulose δ18O

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Needle cell elongation and maturation timing derived from pine needle cellulose δ¹⁸O