Effects of Dissolved Inorganic Carbon and Oxygen Content on the Photosynthetic Characteristics of two Common Tropical Seagrasses Halophila ovalis (R. Br.) Hook. and Thalassia hemprichii (Ehrenb.)

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Pimchanok Buapet
Muhammad Heemboo


We investigated the effects of dissolved inorganic carbon (DIC) and O2 concentrations on photosynthetic characteristics of two common tropical seagrasses, Halophila ovalis and Thalassia hemprichii. In the first series of experiments, leaf segments were incubated in 2.2 mM DIC or DIC-free media. Relative electron transport rates (rETR), non-photochemical quenching (NPQ), and maximum quantum yield of photosystem II (Fv/Fm) were measured under saturating irradiance at air-equilibrated O2 (~300 µM), 3 % of air-equilibrated O2 (~10 µM), and finally at restored air-equilibrated O2 (~300 µM). DIC limitation reduced rETR and increased NPQ, while low O2 reduced rETR and Fv/Fm, indicating that both carbon assimilation and O2 can act as electron sinks. In the second series of experiments, leaf segments were exposed to irradiance of either 400, 1200, 2000 or 2800 μmol photons·m-2·s-1 for 40 min in four different conditions: 1) 2.2 mM DIC, air-equilibrated O2; 2) DIC-free, air-equilibrated O2; 3) 2.2 mM DIC, 3 % of air-equilibrated O2; and 4) DIC-free, 3 % of air-equilibrated O2.  Photoinhibition due to high light exposure was detected; however, no significant effect of DIC or O2 concentration was observed. This result indicates that alternative electron flow was not a crucial component of photoprotective mechanisms at high irradiance.


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Badger, M.R., S. von Caemmerer, S. Ruuska and H. Nakano. 2000. Electron flow to oxygen in higher plants and algae: rates and control of direct photoreduction (Mehler reaction) and Rubisco oxygenase. Philosophical Transactions of the Royal Society B: Biological Sciences 355: 1433-1445.

Beer, S. and J. Rehnberg. 1997. The acquisition of inorganic carbon by the seagrass Zostera marina. Aquatic Botany 56: 277-283.

Beer, S. and M. Björk. 2000. Measuring rates of photosynthesis of two tropical seagrasses by pulse amplitude modulated (PAM) fluorometry. Aquatic Botany 66: 69-76.

Beer, S., M. Mtolera, T. Lyimo and M. Björk. 2006. The photosynthetic performance of the tropical seagrass Halophila ovalis in the upper intertidal. Aquatic Botany 84: 367-371.

Black, C.C., J.E. Burris and R.G. Everson. 1976. The influence of oxygen concentration on photosynthesis in marine plants. Australian Journal of Plant Physiology 3: 81-86.

Brestic, M., G. Cornic, M.J. Fryer and N.R. Baker. 1995. Does photorespiration protect the photosynthetic apparatus in French bean leaves from photoinhibition during drought stress? Planta 196: 450-457.

Buapet, P. and M. Björk. 2016. The role of O2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L. Photosynthesis Research 129(1): 59-69.

Buapet, P., F. Makkliang and C. Thammakhet-Buranachai. 2017. Photosynthetic activity and photoprotection in green and red leaves of the seagrasses, Halophila ovalis and Cymodocea rotundata: implications for the photoprotective role of anthocyanin. Marine Biology 164: 182. DOI: 10.1007/s00227-017-3215-9.

Buapet, P., L.L. Jie Qi and P.A. Todd. 2020. Differing photosynthetic responses to excess irradiance in the two coexisting seagrasses, Halophila ovalis and Halophila decipiens: Chloroplast avoidance movement, chlorophyll fluorescence, and leaf optical properties. Aquatic Botany 166: 103268. DOI: 10.1016/j.aquabot.2020.103268.

Buapet, P., L.M. Rasmusson, M. Gullström and M. Björk. 2013b. Photorespiration and Carbon Limitation Determine Productivity in Temperate Seagrasses. PLoS ONE 8(12): e83804. DOI: 10.1371/journal.pone.008380.

Buapet, P., M. Gullström and M. Björk. 2013a. Photosynthetic activity of seagrasses and macroalgae in temperate shallow waters can alter seawater pH and total inorganic carbon content at the scale of a coastal embayment. Marine and Freshwater Research 64: 1040-1048.

Downton, W.J.S., D.G. Bishop, A.W.D. Larkum and C.B. Osmond. 1976. Oxygen inhibition of photosynthetic oxygen evolution in marine plants. Australian Journal of Plant Physiology 3: 73-79.

Driever, S. M. and N.R. Baker. 2011. The water-water cycle in leaves is not a major alternative electron sink for dissipation of excess excitation energy when CO2 assimilation is restricted. Plant, Cell and Environment 34(5): 837-846. DOI: 10.1111/j.1365-3040.2011.02288.x.

Heber, U. 2002. Irrungen, Wirrungen? The Mehler reaction in relation to cyclic electron transport in C3 plants. Photosynthesis Research 73: 223-231.

Heber, U., R. Bligny, P. Streb and R. Douce. 1996. Photorespiration is essential for the protection of the photosynthetic apparatus of C3 plants against photoinactivation under sunlight. Botanica Acta 109: 307-315.

Jiang, C.D., H.Y. Gao, Q. Zoub, G.M. Jiang and L.H. Li. 2006. Leaf orientation, photorespiration and xanthophyll cycle protect young soybean leaves against high irradiance in field. Environmental and Experimental Botany 55: 87-96.

Kaewsrikhaw, R. and A. Prathep. 2014. The effect of habitats, densities and seasons on morphology, anatomy and pigment content of the seagrass Halophila ovalis (R.Br.) Hook.f. at Haad Chao Mai National Park, Southern Thailand. Aquatic Botany 116: 69-75.

Kaewsrikhaw, R., R.J. Ritchie and A. Prathep. 2016. Variations of tidal exposures and seasons on growth, morphology, anatomy and physiology of the seagrass Halophila ovalis (R.Br.) Hook. f. in a seagrass bed in Trang Province, Southern Thailand. Aquatic Botany 130: 11-20.

Kozaki, A. and G. Takeba. 1996. Photorespiration protects C3 plants from photooxidation. Nature 384: 557-560.

Laisk, A. and E. Edwards. 1998. Oxygen and electron flow in C4 photosynthesis: Mehler reaction, photorespiration and CO2 concentration in the bundle sheath. Planta 205: 632-645.

Laureau, C., R. De Paepe, G. Latouche, M. Moreno-Chacón, G. Finazzi, M. Kuntz, G. Cornic and P. Streb. 2013. Plastid terminal oxidase (PTOX) has the potential to act as a safety valve for excess excitation energy in the alpine plant species Ranunculus glacialis L. Plant Cell and Environment 36: 1296-1310.

Mass, T., A. Genin, U. Shavit, M. Grinstein and D. Tchernov. 2010. Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water. Proceedings of the National Academy of Sciences of the United States of America 107: 2527-2531.

Mvungi, E.F., T.J. Lyimo and M. Björk. 2012. When Zostera marina is intermixed with Ulva, its photosynthesis is reduced by increased pH and lower light, but not by changes in light quality. Aquatic Botany 102: 44-49.

Nogués, S. and L. Alegre. 2002. An increase in water deficit has no impact on the photosynthetic capacity of field-grown Mediterranean plants. Functional Plant Biology 29: 621-630.

Oja, V., H. Eichelmann and A. Laisk. 2011. The size of the lumenal proton pool in leaves during induction and steady-state photosynthesis. Photosynthesis Research 110: 73-88.

Park, YI., W.S. Chow, C.B. Osmond and J. Anderson. 1996. Electron transport to oxygen mitigates against the photoinactivation of Photosystem II in vivo. Photosynthesis Research 50: 23-32.

Phandee, S. and P. Buapet. 2018. Photosynthetic and antioxidant responses of the tropical intertidal seagrasses Halophila ovalis and Thalassia hemprichii to moderate and high irradiances. Botanica Marina 61(3): 247-256.

Ralph, P.J. 1999. Light-induced photoinhibitory stress responses of laboratory-cultured Halophila ovalis. Botanica Marina 42: 11-22.

Ralph, P.J. and R. Gademann. 2005. Rapid light curves: a powerful tool to assess photosynthetic activity. Aquatic Botany 82: 222-237.

Ralph, P.J., S. Polk, K.A. Moore, R.J. Orth and W.A. Smith. 2002. Operation of the xanthophyll cycle in the seagrass Zostera marina in response to variable light. Journal of Experimental Marine Biology and Ecology 271: 189-207.

Rasmusson, L.M., C. Lauritano, G. Procaccini, M. Gullström, P. Buapet and M. Björk. 2017. Respiratory oxygen consumption in the seagrass Zostera marina varies on a diel basis and is partly affected by light. Marine Biology 164(6): 140. DOI: 10.1007/s00227-017-3168-z.

Roberty, S., B. Bailleul, N. Berne, F. Franck and P. Cardol. 2014. PSI Mehler reaction is the main alternative photosynthetic electron pathway in Symbiodinium sp., symbiotic dinoflagellates of cnidarians. New Phytologist 204: 81-91.

Ruuska, S.A., Badger, M.R., Andrews, T.J. and von S. Caemmerer. 2000. Photosynthetic electron sinks in transgenic tobacco with reduced amounts of Rubisco: little evidence for significant Mehler reaction. Journal of Experimental Botany 51: 357-368. DOI: 10.1093/jexbot/51.suppl_1.357.

Silva, J., I. Barrote, M.M. Costa, S. Albano and R. Santos. 2013. Physiological Responses of Zostera marina and Cymodocea nodosa to Light-Limitation Stress. PLoS ONE 8(11): e81058. DOI: 10.1371/journal.pone.0081058.

Shinopoulos, K.E. and G.W. Brudvig. 2012. Cytochrome b559 and cyclic electron transfer within photosystem II. Biochimica et Biophysica Acta 1817: 66-75.