caa a22 4500 469098503 CHVBK 20180323133038.0 cr unu---uuuuu 170328e19920601xx s 000 0 eng 10.1007/BF00317698 doi (NATIONALLICENCE)springer-10.1007/BF00317698 Leaf orientation and the response of the xanthophyll cycle to incident light [Elektronische Daten] [W. Adams III, M. Volk, A. Hoehn, B. Demmig-Adams] Summary: Leaves from two species, Euonymus kiautschovicus and Arctostaphylos uva-ursi, with a variety of different orientations and exposures, were examined in the field with regard to the xanthophyll cycle (the interconversion of three carotenoids in the chloroplast thylakoid membranes). East-, south-, and west-facing leaves of E. kiautschovicus were sampled throughout the day and all exhibited a pronounced and progressive conversion of violaxanthin to zeaxanthin, followed by a reconversion of zeaxanthin to violaxanthin later in the day. Maximal levels of zeaxanthin and minimal levels of violaxanthin were observed at the time when each leaf (orientation) received the maximum incident light, which was in the morning in east-facing, midday in southfacing, and in the afternoon in west-facing leaves. A very slight degree of hysteresis in the removal of zeaxanthin compared to its formation with regard to incident light was observed. Leaves with a broader range of orientations were sampled from A. uva-ursi prior to sunrise and at midday. All of the examined pigments (carotenoids and chlorophylls) increased somewhat per unit leaf area with increasing total daily photon receipt. The sum of the carotenoids involved in the xanthophyll cycle, violaxanthin + antheraxanthin + zeaxanthin, increased more strongly with increasing growth light than any other pigment. In addition, the amounts of zeaxanthin present at midday also increased markedly with increasing total daily photon receipt. The percentage of the xanthophyll cycle that was converted to zeaxanthin (and antheraxanthin) at peak irradiance was very large (approximately 80%) in the leaves of both E. kiautschovicus and A. uva-ursi. The daily changes in the components of the xanthophyll cycle that paralleled the daily changes in incident light in the leaves of E. kiautschovicus, and the increasing levels of the xanthophyll cycle components with total daily photon receipt in the leaves of A. uva-ursi, are both consistent with the involvement of zeaxanthin (i.e. the xanthophyll cycle) in the photoprotection of the photosynthetic apparatus against damage due to excessive light. Springer-Verlag, 1992 Carotenoids nationallicence Photosynthetic apparatus nationallicence Leaf orientation nationallicence Xanthophyll cycle nationallicence Zeaxanthin nationallicence A : antheraxanthin nationallicence EPS : epoxidation state of the xanthophyll cycle=(V+0.5A)/(V+A+Z) nationallicence PFD : photon flux density (400-700 nm) nationallicence PFDi : photon flux density incident upon the upper leaf surface nationallicence Tair : air temperature nationallicence TL : leaf temperature nationallicence V : violaxanthin nationallicence Z : zeaxanthin nationallicence Adams III W. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut Volk M. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut Hoehn A. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut Demmig-Adams B. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut Oecologia Springer-Verlag 90/3(1992-06-01), 404-410 0029-8549 90:3<404 1992 90 442 https://doi.org/10.1007/BF00317698 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00317698 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Adams III W. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut NATIONALLICENCE 700 1- Volk M. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut NATIONALLICENCE 700 1- Hoehn A. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut NATIONALLICENCE 700 1- Demmig-Adams B. Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA aut NATIONALLICENCE 773 0- Oecologia Springer-Verlag 90/3(1992-06-01), 404-410 0029-8549 90:3<404 1992 90 442 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer