The role of O-2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L.
Number of Authors: 2
2016 (English)In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 129, no 1, 59-69 p.Article in journal (Refereed) Published
This study investigates the role of O-2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L. Electron transport rates (ETRs) and non-photochemical quenching (NPQ) of Z. marina were measured under saturating irradiance in synthetic seawater containing 2.2 mM DIC and no DIC with different O-2 levels (air-equilibrated levels, 3 % of air equilibrium and restored air-equilibrated levels). Lowering O-2 did not affect ETR when DIC was provided, while it caused a decrease in ETR and an increase in NPQ in DIC-free media, indicating that O-2 acted as an alternative electron acceptor under low DIC. The ETR and NPQ as a function of irradiance were subsequently assessed in synthetic seawater containing (1) 2.2 mM DIC, air-equilibrated O-2; (2) saturating CO2, no O-2; and (3) no DIC, air-equilibrated O-2. These treatments were combined with glycolaldehyde pre-incubation. Glycolaldehyde caused a marked decrease in ETR in DIC-free medium, indicating significant electron flow supported by photorespiration. Combining glycolaldehyde with O-2 depletion completely suppressed ETR suggesting the operation of the Mehler reaction, a possibility supported by the photosynthesis-dependent superoxide production. However, no notable effect of suppressing the Mehler reaction on NPQ was observed. It is concluded that during DIC-limiting conditions, such as those frequently occurring in the habitats of Z. marina, captured light energy exceeds what is utilised for the assimilation of available carbon, and photorespiration is a major alternative electron acceptor, while the contribution of the Mehler reaction is minor.
Place, publisher, year, edition, pages
2016. Vol. 129, no 1, 59-69 p.
Zostera marina, Photorespiration, Mehler reaction, Chlorophyll fluorescence
IdentifiersURN: urn:nbn:se:su:diva-132570DOI: 10.1007/s11120-016-0268-4ISI: 000378411100006PubMedID: 27125819OAI: oai:DiVA.org:su-132570DiVA: diva2:953586