Mesophyll conductance to CO2 in leaves of Siebold’s beech (Fagus crenata) seedlings under elevated ozone
- 220 Downloads
Ozone is an air pollutant that negatively affects photosynthesis in woody plants. Previous studies suggested that ozone-induced reduction in photosynthetic rates is mainly attributable to a decrease of maximum carboxylation rate (Vcmax) and/or maximum electron transport rate (Jmax) estimated from response of net photosynthetic rate (A) to intercellular CO2 concentration (Ci) (A/Ci curve) assuming that mesophyll conductance for CO2 diffusion (gm) is infinite. Although it is known that Ci-based Vcmax and Jmax are potentially influenced by gm, its contribution to ozone responses in Ci-based Vcmax and Jmax is still unclear. In the present study, therefore, we analysed photosynthetic processes including gm in leaves of Siebold’s beech (Fagus crenata) seedlings grown under three levels of ozone (charcoal-filtered air or ozone at 1.0- or 1.5-times ambient concentration) for two growing seasons in 2016–2017. Leaf gas exchange and chlorophyll fluorescence were simultaneously measured in July and September of the second growing season. We determined the A, stomatal conductance to water vapor and gm, and analysed A/Ci curve and A/Cc curve (Cc: chloroplast CO2 concentration). We also determined the Rubisco and chlorophyll contents in leaves. In September, ozone significantly decreased Ci-based Vcmax. At the same time, ozone decreased gm, whereas there was no significant effect of ozone on Cc-based Vcmax or the contents of Rubisco and chlorophyll in leaves. These results suggest that ozone-induced reduction in Ci-based Vcmax is a result of the decrease in gm rather than in carboxylation capacity. The decrease in gm by elevated ozone was offset by an increase in Ci, and Cc did not differ depending on ozone treatment. Since Cc-based Vcmax was also similar, A was not changed by elevated ozone. We conclude that gm is an important factor for reduction in Ci-based Vcmax of Siebold’s beech under elevated ozone.
KeywordsChlorophyll fluorescence Mesophyll conductance Ozone Photosynthesis Siebold’s beech Vcmax
The authors are greatly indebted to Dr. Kazuhide Matsuda and Mr. Hiroyuki Ozawa (Tokyo University of Agriculture and Technology) for their technical support. The authors would like to thank the editor and two anonymous reviewers for providing valuable comments on an earlier version of the manuscript. This study was supported by JSPS KAKENHI, Young Scientists B (15K16136 to MW), Type B (18H03410 to TI and MW) and Challenging Exploratory Research (15K12217 to TI and MW).
- Flexas J, Barbour MM, Brendel O, Cabrera HM, Carriqui M, Díaz-Espejo A, Douthe C, Dreyer E, Ferrio JP, Gago J, Galmés J, Kodama N, Medrano H, Niinemets Ü, Peguero-Pina J, Pou A, Ribas-Carbó M, Tomás M, Tosens T, Warren CR (2012) Mesophyll diffusion conductance to CO2: an unappreciated central player in photosynthesis. Plant Sci 193:70–84CrossRefGoogle Scholar
- Hartmann DL, Klein Tank AMG, Rusticucci M, Alexander LV, Brönnimann S, Charabi Y, Dentener FJ, Dlugokencky EJ, Easterling DR, Kaplan A, Soden BJ, Thorne PW, Wild M, Zhai PM (2013) Observations: atmosphere and surface. In: Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds) Climate change 2013. The physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, pp 159–254Google Scholar
- Koike T, Watanabe M, Hoshika Y, Kitao M, Matsumura H, Funada R, Izuta T (2013) Effects of ozone on forest ecosystems in East and Southeast Asia. In: Matyssek R, Clarke N, Cudlin P, Mikkelsen TN, Tuovinen J-P, Wieser G, Paoletti E (eds) Climate change, air pollution and global challenges: understanding and perspectives from forest research. Elsevier, Oxford, pp 371–390CrossRefGoogle Scholar
- Paoletti E, Schaub M, Matyssek R, Wieser G, Augustaitis A, Bastrup-Birk AM, Bytnerowicz A, Günthardt-Goerg MS, Müller-Starck G, Serengil Y (2010) Advances of air pollution science: from forest decline to multiple-stress effects on forest ecosystem services. Environ Pollut 158:1986–1989CrossRefGoogle Scholar
- R Development Core Team (2017) R: a language and environment for statistical computing. R Foundation for Statistical Computing. http://www.R-project.org. Accessed 17 Jan 2018
- Schreiber U, Bilger W, Neubauer C (1994) Chlorophyll fluorescence as a nonintrusive indicator for rapid assessment of in vivo photosynthesis. In: Schulze E-D, Caldwell MM (eds) Ecophysiology of photosynthesis. Springer, Berlin, pp 49–70Google Scholar
- von Caemmerer S (2000) Biochemical models of leaf photosynthesis. CSIRO Publishing, CollingwoodGoogle Scholar