Dataset Information

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

ABSTRACT: The 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.

SUBMITTER: Adnew GA

PROVIDER: S-EPMC8263724 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature

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

Adnew Getachew Agmuas GA Hofmann Magdalena E G MEG Pons Thijs L TL Koren Gerbrand G Ziegler Martin M Lourens Lucas J LJ Röckmann Thomas T

Scientific reports 20210707 1

The 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 Δ<su ...[more]

PMID: 34234170

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Project description:BackgroundPhotosynthesis of reproductive organs in C3 cereals is generally regarded as important to crop yield. Whereas, photosynthetic characteristics of reproductive organs are much less understood as compared to leaf photosynthesis, mainly due to methodological limitations. To date, many indirect methods have been developed to study photosynthesis of reproductive organs and its contribution to grain yield, such as organ shading, application of herbicides and photosynthetic measurement of excised organs or tissues, which might be intrusive and cause biases. Thus, a robust and in situ approach needs to be developed.ResultsHere we report the development of a custom-built panicle photosynthesis chamber (P-chamber), which can be connected to standard infrared gas analyzers to study photosynthetic/respiratory rate of a rice panicle. With the P-chamber, we measured panicle photosynthetic characteristics of seven high-yielding elite japonica, japonica-indica hybrid and indica rice cultivars. Results show that, (1) rice panicle is photosynthetically active during grain filling, and there are substantial inter-cultivar variations in panicle photosynthetic and respiratory rates, no matter on a whole panicle basis, on an area basis or on a single spikelet basis; (2) among the seven testing cultivars, whole-panicle gross photosynthetic rates are 17-54 nmol s-1 5 days after heading under photon flux density (PFD) of 2000 μmol (photons) m-2 s-1, which represent some 20-38% of that of the corresponding flag leaves; (3) rice panicle photosynthesis has higher apparent CO2 compensation point, light compensation point and apparent CO2 saturation point, as compared to that of a typical leaf; (4) there is a strong and significant positive correlation between gross photosynthetic rate 5 days after heading on a single spikelet basis and grain setting rate at harvest (Pearson correlation coefficient r = 0.93, p value < 0.0001).ConclusionsRice panicle gross photosynthesis is significant, has great natural variation, and plays an underappreciated role in grain yield formation. The P-Chamber can be used as a tool to study in situ photosynthetic characteristics of irregular non-foliar plant organs, such as ears, culms, leaf sheaths, fruits and branches, which is a relatively less explored area in current cereal breeding community.

Dataset Information

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

Publications

Leaf scale quantification of the effect of photosynthetic gas exchange on Δ<sub>47</sub> of CO<sub>2</sub>.

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