Unequal allocation of excitation energy between photosystem II and I reduces cyanolichen photosynthesis in blue light.
Photosynthesis was compared in two cyanobacterial lichens (Lobaria hallii and Peltigera praetextata) and two green algal lichens (Lobaria pulmonaria and Peltigera leucophlebia) exposed to red, green or blue light. Cyanolichens had substantially lower photosynthetic CO(2) uptake and O(2) evolution than the green algal lichens in blue light, but slightly higher photosynthesis in red and green light. The effective quantum yield of photosystem (PS) II (Φ(PSII)) decreased with increasing red and green light for all species, but in blue light this response occurred in green algal lichens only. Cyanolichen Φ(PSII) increased with increasing blue light at low irradiances, but decreased at stronger exposures. However, after adding red light the efficiency of blue light for photosynthetic O(2) evolution increased by 2.4 times. Because phycobilisomes associated with PSII have a low blue light absorption, our results are consistent with blue light absorption mainly by Chl in PSI. Thereby, unequal allocation of excitation energy between PSII and PSI results in low cyanolichen photosynthesis under blue light. This is new knowledge in the science of lichenology with important implications for e.g. the reliability of using Chl fluorometers with blue light for cyanolichens.
Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, PO Box 5003, NO-1432 Ås, Norway knut.solhaug@nmbu.no.
Knut Asbjørn
KA
Solhaug
Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, PO Box 5003, NO-1432 Ås, Norway.
Li
L
Xie
Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, PO Box 5003, NO-1432 Ås, Norway.
Yngvar
Y
Gauslaa
D001203:Ascomycota / Q000502:physiology* / Q000528:radiation effects; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000460:Chlorophyta / Q000502:physiology* / Q000528:radiation effects; D000458:Cyanobacteria / Q000502:physiology* / Q000528:radiation effects; D004579:Electron Transport; D008011:Lichens / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D045524:Phycobilisomes / Q000378:metabolism
D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D045524:Phycobilisomes; D002734:Chlorophyll; D002245:Carbon Dioxide; D010100:Oxygen
Electron transport rate; Lichen photobionts; Light quality; Lobaria; Peltigera; Phycobilisomes