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252. Caveats on tomographic images

Author

Foulger, Gillian R., primary, Panza, Giuliano F., additional, Artemieva, Irina M., additional, Bastow, Ian D., additional, Cammarano, Fabio, additional, Evans, John R., additional, Hamilton, Warren B., additional, Julian, Bruce R., additional, Lustrino, Michele, additional, Thybo, Hans, additional, and Yanovskaya, Tatiana B., additional

Published
2013
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253. Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

Author

Osborn, Hannah L., Alonso-Cantabrana, Hugo, Sharwood, Robert E., Covshoff, Sarah, Evans, John R., Furbank, Robert T., and von Caemmerer, Susanne

Subjects
CARBONIC anhydrase, MESOPHYLL tissue, CYTOSOL, PHOSPHOENOLPYRUVIC carboxylase, PYRUVATE kinase, PHOTOSYNTHESIS
Abstract

In C4 species, the major β-carbonic anhydrase (β-CA) localized in the mesophyll cytosol catalyses the hydration of CO2 to HCO3-, which phosphoenolpyruvate carboxylase uses in the first step of C4 photosynthesis. To address the role of CA in C4 photosynthesis, we generated transgenic Setaria viridis depleted in β-CA. Independent lines were identified with as little as 13% of wild-type CA. No photosynthetic defect was observed in the transformed lines at ambient CO2 partial pressure (pCO2). At low pCO2, a strong correlation between CO2 assimilation rates and CA hydration rates was observed. C18O16O isotope discrimination was used to estimate the mesophyll conductance to CO2 diffusion from the intercellular air space to the mesophyll cytosol (gm) in control plants, which allowed us to calculate CA activities in the mesophyll cytosol (Cm). This revealed a strong relationship between the initial slope of the response of the CO2 assimilation rate to cytosolic pCO2 (ACm) and cytosolic CA activity. However, the relationship between the initial slope of the response of CO2 assimilation to intercellular pCO2 (ACi) and cytosolic CA activity was curvilinear. This indicated that in S. viridis, mesophyll conductance may be a contributing limiting factor alongside CA activity to CO2 assimilation rates at low pCO2. [ABSTRACT FROM AUTHOR]

Published
2017
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254. Online CO2 and H2O oxygen isotope fractionation allows estimation of mesophyll conductance in C4 plants, and reveals that mesophyll conductance decreases as leaves age in both C4 and C3 plants.

Author

Barbour, Margaret M., Evans, John R., Simonin, Kevin A., and Caemmerer, Susanne

Subjects
*MESOPHYLL tissue, *PHOTOSYNTHESIS, *PLANT fibers, *PLANT shoots, COTTON genetics
Abstract

Mesophyll conductance significantly, and variably, limits photosynthesis but we currently have no reliable method of measurement for C4 plants., An online oxygen isotope technique was developed to allow quantification of mesophyll conductance in C4 plants and to provide an alternative estimate in C3 plants. The technique is compared to an established carbon isotope method in three C3 species., Mesophyll conductance of C4 species was similar to that in the C3 species measured, and declined in both C4 and C3 species as leaves aged from fully expanded to senescing. In cotton leaves, simultaneous measurement of carbon and oxygen isotope discrimination allowed the partitioning of total conductance to the chloroplasts into cell wall and plasma membrane versus chloroplast membrane components, if CO2 was assumed to be isotopically equilibrated with cytosolic water, and the partitioning remained stable with leaf age., The oxygen isotope technique allowed estimation of mesophyll conductance in C4 plants and, when combined with well-established carbon isotope techniques, may provide additional information on mesophyll conductance in C3 plants. [ABSTRACT FROM AUTHOR]

Published
2016
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294. Cover Image.

Author

Wu, Alex, Brider, Jason, Busch, Florian A., Chen, Min, Chenu, Karine, Clarke, Victoria C., Collins, Brian, Ermakova, Maria, Evans, John R., Farquhar, Graham D., Forster, Britta, Furbank, Robert T., Groszmann, Michael, Hernandez‐Prieto, Miguel A., Long, Benedict M., Mclean, Greg, Potgieter, Andries, Price, G. Dean, Sharwood, Robert E., and Stower, Michael

Subjects
CROP growth, CROP yields
Published
2023
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