caa a22 4500 477100899 CHVBK 20180405111541.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF00620064 doi (NATIONALLICENCE)springer-10.1007/BF00620064 Xanthophyll cycle and light stress in nature: uniform response to excess direct sunlight among higher plant species [Elektronische Daten] [Barbara Demmig-Adams, William Adams III] Photosystem II (PS II) efficiency, nonphotochemical fluorescence quenching, and xanthophyll cycle composition were determined in situ in the natural environment at midday in (i) a range of differently angled sun leaves ofEuonymus kiautschovicus Loesener and (ii) in sun leaves of a wide range of different plant species, including trees, shrubs, and herbs. Very different degrees of light stress were experienced by these leaves (i) in response to different levels of incident photon flux densities at similar photosynthetic capacities amongEuonymus leaves and (ii) as a result of very different photosynthetic capacities among species at similar incident photon flux densities (that were equivalent to full sunlight). ForEuonymus as well as the interspecific comparison all data fell on one single, close relationship for changes in intrinsic PSII efficiency, nonphotochemical fluorescence quenching, or the levels of zeaxanthin + antheraxanthin in leaves, respectively, as a function of the actual level of light stress. Thus, the same conversion state of the xanthophyll cycle and the same level of energy dissipation were observed for a given degree of light stress independent of species or conditions causing the light stress. Since all increases in thermal energy dissipation were associated with increases in the levels of zeaxanthin + antheraxanthin in these leaves, there was thus no indication of any form of xanthophyll cycle-independent energy dissipation in any of the twenty-four species or varieties of plants examined in their natural environment. It is also concluded that transient diurnal changes in intrinsic PSII efficiency in nature are caused by changes in the efficiency with which excitation energy is delivered from the antennae to PSII centers, and are thus likely to be purely photoprotective. Consequently, the possibility of quantifying the allocation of absorbed light into PSII photochemistry versus energy dissipation in the antennae from changes in intrinsic PSII efficiency is explored. Springer-Verlag, 1996 Chlorophyll fluorescence nationallicence Energy dissipation nationallicence Photosynthesis nationallicence Photosystem II nationallicence Xanthophyll cycle nationallicence Zeaxanthin nationallicence A : antheraxanthin nationallicence F : actual level of fluorescence nationallicence Fa, Fo′ : minimal fluorescence in the absence, presence of thylakoid energization nationallicence Fm, Fm′ : maximal fluorescence in the absence, presence of thylakoid energization nationallicence Fm, - F)/Fm′ : actual PSII efficiency ( = percent of absorbed light utilized in PSII photochemistry) nationallicence Fv/Fm, Fv′/Fm/′ : PSII efficiency of open centers in the absence, presence of thylakoid energization nationallicence NPQ : nonphotochemical fluorescence quenching nationallicence Fm/Fm′ - 1 nationallicence qp : quenching coefficient for photochemical quenching nationallicence V : violaxanthin nationallicence Z : zeaxanthin nationallicence Demmig-Adams Barbara Department of Environmental, Population, and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut Adams III William Department of Environmental, Population, and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut Planta Springer-Verlag 198/3(1996-09-01), 460-470 0032-0935 198:3<460 1996 198 425 https://doi.org/10.1007/BF00620064 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00620064 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Demmig-Adams Barbara Department of Environmental, Population, and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut NATIONALLICENCE 700 1- Adams III William Department of Environmental, Population, and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut NATIONALLICENCE 773 0- Planta Springer-Verlag 198/3(1996-09-01), 460-470 0032-0935 198:3<460 1996 198 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer