Photosynthetic gas exchange and the stable isotope composition of leaf water: comparison of a xylem-tapping mistletoe and its host

1993 ◽  
Vol 16 (6) ◽  
pp. 623-631 ◽  
Author(s):  
L. B. FLANAGAN ◽  
J. D. MARSHALL ◽  
J. R. EHLERINGER
Keyword(s):  
Stable Isotope ◽  
Gas Exchange ◽  
Isotope Composition ◽  
Leaf Water ◽  
Stable Isotope Composition ◽  
Photosynthetic Gas Exchange

The dominant environmental driver of leaf water stable isotope enrichment differs for H-2 compared to O-18

2020 ◽  
Author(s):  
Matthias Cuntz ◽  
Lucas A Cernusak ◽  
Keyword(s):  
Stable Isotope ◽  
Relative Humidity ◽  
Air Temperature ◽  
Gordon Equation ◽  
Isotope Composition ◽  
Environmental Variable ◽  
Leaf Water ◽  
Source Water ◽  
Stable Isotope Composition ◽  
Water Stable Isotope

<p>Several important isotopic biomarkers derive at least part of their signal from the stable isotope composition of leaf water (e.g., leaf wax δ<sup>2</sup>H, cellulose δ<sup>2</sup>H and δ<sup>18</sup>O, lignin δ<sup>18</sup>O). In order to interpret these isotopic proxies, it is therefore helpful to know which environmental variable most strongly controls a given leaf water stable isotope signal. We collated observations of the stable isotope compositions of leaf water, xylem water, and atmospheric vapour, along with air temperature and relative humidity, to test whether the dominant driver of leaf water <sup>2</sup>H concentration could differ from that of <sup>18</sup>O concentration. Our dataset comprises 690 observations from 35 sites with broad geographical coverage. We limited our analysis to daytime observations, when the photosynthetic processes that incorporate the leaf water isotopic signal primarily take place. The Craig-Gordon equation was generally a good predictor for daytime bulk leaf water stable isotope composition for both δ<sup>2</sup>H (R<sup>2</sup>=0.86, p<0.001) and δ<sup>18</sup>O (R<sup>2</sup>=0.63, p<0.001). It showed about 10% admixture of source water was caused by unenriched water pools such as leaf veins or the Péclet effect. Solving the Craig-Gordon equation requires knowledge of relative humidity, air temperature, and the stable isotope compositions of source water and atmospheric vapour. However, it is not possible to invert the Craig-Gordon equation to solve for one of these parameters unless the others are known. Here we show that the two isotopic signals of δ<sup>2</sup>H and δ<sup>18</sup>O are predominantly driven by different environmental variables: leaf water δ<sup>2</sup>H correlated most strongly with the δ<sup>2</sup>H of source water (R<sup>2</sup>=0.68, p<0.001) and atmospheric vapour (R<sup>2</sup>=0.63, p<0.001), whereas leaf water δ<sup>18</sup>O correlated most strongly with air relative humidity (R<sup>2</sup>=0.46, p<0.001). We conclude that these two isotopic signals of leaf water are not simply mirror images of the same environmental information, but carry distinct signals of different climate factors, with crucial implications for the interpretation of downstream isotopic biomarkers.</p>

scholarly journals Leaf scale quantification of the effect of photosynthetic gas exchange on Δ47 of CO2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Getachew Agmuas Adnew ◽  
Magdalena E. G. Hofmann ◽  
Thijs L. Pons ◽  
Gerbrand Koren ◽  
Martin Ziegler ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Isotope Composition ◽  
Diffusion Flux ◽  
Leaf Water ◽  
Back Diffusion ◽  
Ambient Conditions ◽  
Photosynthetic Gas Exchange ◽  
O Isotope ◽  
Clumped Isotope ◽  
Kinetic Fractionation

AbstractThe clumped isotope composition (Δ47, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO2 has been suggested as an additional tracer for gross CO2 fluxes. However, the effect of photosynthetic gas exchange on Δ47 has not been directly determined and two indirect/conceptual studies reported contradicting results. In this study, we quantify the effect of photosynthetic gas exchange on Δ47 of CO2 using leaf cuvette experiments with one C4 and two C3 plants. The experimental results are supported by calculations with a leaf cuvette model. Our results demonstrate the important roles of the Δ47 value of CO2 entering the leaf, kinetic fractionation as CO2 diffuses into, and out of the leaf and CO2–H2O isotope exchange with leaf water. We experimentally confirm the previously suggested dependence of Δ47 of CO2 in the air surrounding a leaf on the stomatal conductance and back-diffusion flux. Gas exchange can enrich or deplete the Δ47 of CO2 depending on the Δ47 of CO2 entering the leaf and the fraction of CO2 exchanged with leaf water and diffused back to the atmosphere, but under typical ambient conditions, it will lead to a decrease in Δ47.

Advances in the study of stable isotope composition of leaf water in plants

2013 ◽  
Vol 33 (4) ◽  
pp. 1031-1041 ◽  
Author(s):  
罗伦 LUO Lun ◽  
余武生 YU Wusheng ◽  
万诗敏 WAN Shimin ◽  
周平 ZHOU Ping
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Leaf Water ◽  
Stable Isotope Composition

scholarly journals Leaf-scale quantification of the effect of photosynthetic gas exchange on Δ<sup>17</sup>O of atmospheric CO<sub>2</sub>

2020 ◽  
Author(s):  
Getachew Agmuas Adnew ◽  
Thijs L. Pons ◽  
Gerbrand Koren ◽  
Wouter Peters ◽  
Thomas Röckmann
Keyword(s):  
Gas Exchange ◽  
Oxygen Isotope ◽  
Mole Fraction ◽  
Isotope Composition ◽  
Leaf Water ◽  
Oxygen Isotope Composition ◽  
Atmospheric Co2 ◽  
C3 Plants ◽  
Back Diffusion ◽  
Photosynthetic Gas Exchange

Abstract. Understanding the processes that affect the triple oxygen isotope composition of atmospheric CO2 during gas exchange can help constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions, using three plant species. The experiments were conducted at two different light intensities and using CO2 with different 17O-excess. The oxygen isotope composition of CO2 was used to estimate cm, the mole fraction of CO2 at the CO2-H2O exchange site. Our results demonstrate that two key factors determine the effect of gas exchange on the Δ17O of atmospheric CO2. The relative difference between Δ17O of the CO2 entering the leaf and the CO2 in equilibrium with leaf water, and the back-diffusion flux of CO2 from the leaf to the atmosphere, which can be quantified by the cm/ca ratio where ca is the CO2 mole fraction in the surrounding air. At low cm/ca ratio the discrimination is governed mainly by diffusion into the leaf, and at high cm/ca ratio by back-diffusion of CO2 that has equilibrated with the leaf water. Plants with a higher cm/ca ratio modify the Δ17O of atmospheric CO2 more strongly than plants with a lower cm/ca ratio. Based on the leaf cuvette experiments, the global value for discrimination against Δ17O of atmospheric CO2 during the photosynthetic gas exchange is estimated to be −0.57+/−0.14 ‰ using cm/ca values of 0.3 and 0.7 for C4 and C3 plants, respectively. The main uncertainties in this global estimate arise from variation in cm/ca ratios among plants and growth conditions.

scholarly journals Leaf-scale quantification of the effect of photosynthetic gas exchange on Δ<sup>17</sup>O of atmospheric CO<sub>2</sub>

2020 ◽  
Vol 17 (14) ◽  
pp. 3903-3922
Author(s):  
Getachew Agmuas Adnew ◽  
Thijs L. Pons ◽  
Gerbrand Koren ◽  
Wouter Peters ◽  
Thomas Röckmann
Keyword(s):  
Gas Exchange ◽  
Oxygen Isotope ◽  
Isotope Composition ◽  
Diffusion Flux ◽  
Leaf Water ◽  
Atmospheric Co2 ◽  
C3 Plants ◽  
Back Diffusion ◽  
Photosynthetic Gas Exchange ◽  
Oxygen Isotope Exchange

Abstract. Understanding the processes that affect the triple oxygen isotope composition of atmospheric CO2 during gas exchange can help constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions using three plant species. The experiments were conducted at two different light intensities and using CO2 with different Δ17O. We directly quantify the effect of photosynthesis on Δ17O of atmospheric CO2 for the first time. Our results demonstrate the established theory for δ18O is applicable to Δ17O(CO2) at leaf level, and we confirm that the following two key factors determine the effect of photosynthetic gas exchange on the Δ17O of atmospheric CO2. The relative difference between Δ17O of the CO2 entering the leaf and the CO2 in equilibrium with leaf water and the back-diffusion flux of CO2 from the leaf to the atmosphere, which can be quantified by the cm∕ca ratio, where ca is the CO2 mole fraction in the surrounding air and cm is the one at the site of oxygen isotope exchange between CO2 and H2O. At low cm∕ca ratios the discrimination is governed mainly by diffusion into the leaf, and at high cm∕ca ratios it is governed by back-diffusion of CO2 that has equilibrated with the leaf water. Plants with a higher cm∕ca ratio modify the Δ17O of atmospheric CO2 more strongly than plants with a lower cm∕ca ratio. Based on the leaf cuvette experiments, the global value for discrimination against Δ17O of atmospheric CO2 during photosynthetic gas exchange is estimated to be -0.57±0.14 ‰ using cm∕ca values of 0.3 and 0.7 for C4 and C3 plants, respectively. The main uncertainties in this global estimate arise from variation in cm∕ca ratios among plants and growth conditions.

Leaf-scale quantification of the effect of photosynthetic gas exchange on Δ17O of atmospheric CO2

2020 ◽  
Author(s):  
Getachew Adnew ◽  
Thijs Pons ◽  
Gerbrand Koren ◽  
Wouter Peters ◽  
Thomas Röckmann
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Photosynthetic Capacity ◽  
Isotope Composition ◽  
Diffusion Flux ◽  
Relative Difference ◽  
Leaf Water ◽  
Back Diffusion ◽  
Photosynthetic Gas Exchange ◽  
High Photosynthetic Capacity

&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Understanding the processes affecting the triple oxygen isotope composition of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; during photosynthesis can help to constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions, using sunflower (&lt;em&gt;Helianthus annuus&lt;/em&gt;), an annual C&lt;sub&gt;3&lt;/sub&gt; species with high photosynthetic capacity and stomatal conductance for CO&lt;sub&gt;2&lt;/sub&gt;, an evergreen C&lt;sub&gt;3&lt;/sub&gt; species, ivy (&lt;em&gt;Hedera hybernica&lt;/em&gt;) with lower values for these traits, and a C&lt;sub&gt;4&lt;/sub&gt; species maize (&lt;em&gt;Zea mays)&lt;/em&gt; that has a high photosynthetic capacity and low stomatal conductance. The experiments were conducted at different light intensities and using CO&lt;sub&gt;2&lt;/sub&gt; with different &lt;sup&gt;17&lt;/sup&gt;O- excess. Our results demonstrate that two key factors determine the effect of photosynthetic gas exchange on &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of atmospheric CO&lt;sub&gt;2&lt;/sub&gt;: The relative difference in &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of the CO&lt;sub&gt;2&lt;/sub&gt; entering the leaf and &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of leaf water, and the back-diffusion flux from the leaf to the atmosphere, which can be quantified by the c&lt;sub&gt;m&lt;/sub&gt;/c&lt;sub&gt;a&lt;/sub&gt; ratio.&amp;#160; At low c&lt;sub&gt;m&lt;/sub&gt;/c&lt;sub&gt;a&lt;/sub&gt; the discrimination is governed by diffusion into the leaf, and at high c&lt;sub&gt;m&lt;/sub&gt;/c&lt;sub&gt;a&lt;/sub&gt; by back-diffusion of CO&lt;sub&gt;2&lt;/sub&gt; that has equilibrated with the leaf water. Plants with a higher c&lt;sub&gt;m&lt;/sub&gt;/c&lt;sub&gt;a&lt;/sub&gt; ratio modify the &amp;#916;&lt;sup&gt;17&lt;/sup&gt;O of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; more strongly than plants with lower c&lt;sub&gt;m&lt;/sub&gt;/c&lt;sub&gt;a&lt;/sub&gt;.&amp;#160;&lt;/p&gt;&lt;p&gt;Based on the leaf cuvette experiments using both C&lt;sub&gt;4&lt;/sub&gt; and C&lt;sub&gt;3&lt;/sub&gt; plants, the global discrimination in &lt;sup&gt;17&lt;/sup&gt;O-excess of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; due to assimilation is estimated to be -0.6&amp;#177;0.2&amp;#8240;. The main uncertainty in the global estimation is due to the uncertainty in the c&lt;sub&gt;m&lt;/sub&gt;/c&lt;sub&gt;a&lt;/sub&gt; ratio.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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