Regular Paper

Photosynthesis Research

, Volume 107, Issue 3, pp 223-235

First online:

The interrelationship between the lower oxygen limit, chlorophyll fluorescence and the xanthophyll cycle in plants

  • A. Harrison WrightAffiliated withAtlantic Food and Horticulture Research Centre, Agriculture and Agri-Food CanadaDepartment of Biology, Dalhousie University Email author 
  • , John M. DeLongAffiliated withAtlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada
  • , Arunika H. L. A. N. GunawardenaAffiliated withDepartment of Biology, Dalhousie University
  • , Robert K. PrangeAffiliated withAtlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada

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The lower oxygen limit (LOL) in plants may be identified through the measure of respiratory gases [i.e. the anaerobic compensation point (ACP) or the respiratory quotient breakpoint (RQB)], but recent work shows it may also be identified by a sudden rise in dark minimum fluorescence (F o). The interrelationship between aerobic respiration and fermentative metabolism, which occur in the mitochondria and cytosol, respectively, and fluorescence, which emanates from the chloroplasts, is not well documented in the literature. Using spinach (Spinacia oleracea), this study showed that Fo and photochemical quenching (q P) remained relatively unchanged until O2 levels dropped below the LOL. An over-reduction of the plastoquinone (PQ) pool is believed to increase F o under dark + anoxic conditions. It is proposed that excess cytosolic reductant due to inhibition of the mitochondria’s cytochrome oxidase under low-O2, may be the primary reductant source. The maximum fluorescence (F m) is largely unaffected by low-O2 in the dark, but was severely quenched, mirroring changes to the xanthophyll de-epoxidation state (DEPS), under even low-intensity light (≈4 μmol m−2 s−1). In low light, the low-O2-induced increase in F o was also quenched, likely by non-photochemical and photochemical means. The degree of quenching in the light was negatively correlated with the level of ethanol fermentation in the dark. A discussion detailing the possible roles of cyclic electron flow, the xanthophyll cycle, chlororespiration and a pathway we termed ‘chlorofermentation’ were used to interpret fluorescence phenomena of both spinach and apple (Malus domestica) over a range of atmospheric conditions under both dark and low-light.


Chlorofermentation Chlororespiration Fermentation Non-photochemical quenching Photochemical quenching Xanthophyll cycle