caa a22 4500 397521065 CHVBK 20180308164632.0 cr unu---uuuuu 161202e199509 xx s 000 0 eng 10.1093/jxb/46.special_issue.1351 doi (NATIONALLICENCE)oxford-10.1093/jxb/46.special_issue.1351 Perspectives on photoinhibition and photorespiration in the field: quintessential inefficiencies of the light and dark reactions of photosynthesis? [Elektronische Daten] [C.B. Osmond, S.C. Grace] Taking the long-held view that photoinhibition embraces several processes leading to a reduction in the efficiency of light utilization in photosynthesis, and that photorespiration embraces several processes associated with O2 uptake in the light, photoinhibition and photorespiration now can be considered as inevitable, but essential inefficiencies of photosynthesis which help preserve photosynthetic competence in bright light. Photorespiratory O2 uptake via Rubisco, and O2 uptake via the Mehler reaction, both promote non-assimilatory electron transport, and stimulate photon utilization during CO2-limited photosynthesis in bright light. Although fluorescence studies show that the proportion of total photon use via oxygenase photorespiration in air may decline to only about 10% in full sunlight, mass spectrometer studies show that O2 uptake in Mehler reaction photorespiration in C3 and CAM plants can still account for up to 50% of electron flow in saturating CO2 and light. The Mehler-ascorbate peroxidase reaction has an additional role in sustaining membrane energization which promotes dynamic photoinhibition and photon protection (rapidly reversible decrease in PSII efficiency involving dissipation of the energy of excess photons in the antennae). Net CO2 and O2 exchange studies evidently underestimate the extent of total electron transport, and hence overestimate the extent of photon excess in bright light, leading to overestimates of the role of energy-dependent photon dissipation through dynamic photo-inhibition. Nevertheless, in C3 plants in air all of these processes help to mitigate chronic photoinhibition and photon damage (slowly reversible decrease in PSII efficiency involving loss of reaction centre function). The possibility remains that residual electron transport to O2 from intermediates in the vicinity of PSII may also lead to reactive O2 species that potentiate this photon damage. © 1995 Oxford University Press Photorespiration: Alternative Pathways: Carbon Allocation nationallicence Photoinhibition nationallicence photorespiration nationallicence photosynthesis nationallicence light reaction nationallicence dark reaction nationallicence Osmond C.B. Research School of Biological Sciences, Institute of Advanced Studies, The Australian National University Box 475, Canberra ACT2601, Australia aut Grace S.C. Department of Botany, Duke University Durham, NC 27708, USA aut Journal of Experimental Botany Oxford University Press 46/special_issue(1995-09), 1351-1362 0022-0957 46:special_issue<1351 1995 46 exbotj https://doi.org/10.1093/jxb/46.special_issue.1351 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/jxb/46.special_issue.1351 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Osmond C.B. Research School of Biological Sciences, Institute of Advanced Studies, The Australian National University Box 475, Canberra ACT2601, Australia aut NATIONALLICENCE 700 1- Grace S.C. Department of Botany, Duke University Durham, NC 27708, USA aut NATIONALLICENCE 773 0- Journal of Experimental Botany Oxford University Press 46/special_issue(1995-09), 1351-1362 0022-0957 46:special_issue<1351 1995 46 exbotj Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford