, Volume 198, Issue 3, pp 460–470

Xanthophyll cycle and light stress in nature: uniform response to excess direct sunlight among higher plant species


DOI: 10.1007/BF00620064

Cite this article as:
Demmig-Adams, B. & Adams, W.W. Planta (1996) 198: 460. doi:10.1007/BF00620064


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.

Key words

Chlorophyll fluorescence Energy dissipation Photosynthesis Photosystem II Xanthophyll cycle Zeaxanthin 





actual level of fluorescence

Fa, Fo

minimal fluorescence in the absence, presence of thylakoid energization

Fm, Fm

maximal fluorescence in the absence, presence of thylakoid energization

Fm, - F)/Fm

actual PSII efficiency ( = percent of absorbed light utilized in PSII photochemistry)

Fv/Fm, Fv/Fm/′

PSII efficiency of open centers in the absence, presence of thylakoid energization


nonphotochemical fluorescence quenching

Fm/Fm - 1; qp

quenching coefficient for photochemical quenching





Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  1. 1.Department of Environmental, Population, and Organismic BiologyUniversity of ColoradoBoulderUSA