title: The non-photochemical reduction of plastoquinone in leaves.
abstract: Although it is generally assumed that the plastoquinone pool of thylakoid membranes in leaves of higher plants is rapidly oxidized upon darkening, this is often not the case. A multiflash kinetic fluorimeter was used to monitor the redox state of the plastoquinone pool in leaves. It was found that in many species of plants, particularly those using the NAD-malic enzyme C4 system of photosynthesis, the pool actually became more reduced following a light to dark transition. In some Amaranthus species, plastoquinone remained reduced in the dark for several hours. Far red light, which preferentially drives Photosystem I turnover, could effectively oxidize the plastoquinone pool. Plastoquinone was re-reduced in the dark within a few seconds when far red illumination was removed. The underlying mechanism of the dark reduction of the plastoquinone pool is still uncertain but may involve chlororespiratory activity.
authors: Photosynthesis Research Unit of USDA/ARS, University of Illinois, 61801, Urbana, IL, USA.
authors: Q J
authors: QJ
authors: Groom
authors: D M
authors: DM
authors: Kramer
authors: A R
authors: AR
authors: Crofts
authors: D R
authors: DR
authors: Ort