Abstract
The redox state of the primary quinone acceptor (Q A) of photosystem II (PS II) and specific non-photochemical effects determine the relation between PS II photochemistry and chlorophyll fluorescence. For the unicellular green alga Scenedesmus obliquus, the fluorescence yield ( F), the fluorescence yield in the presence of reduced Q A ( F M′) and the yield of respiration-corrected oxygen evolution (ф ox, evolution rate divided by light intensity) were determined during exposure to actinic light of various intensities (0.1 – 1600 μE m −2 s −1). Irrespective of the growth conditions, the parameter ф p = (F M ′ − F)/F M ′ was found to be proportional to ф ox for each algal culture. This finding is in full agreement with non-photochemical fluorescence quenching by increased thermal deactivation of excited antenna states, but is difficult to reconcile with non-photochemical quenching due to modified PS II electron transfer reactions. In particular, no indications of cyclic PS II electron flow were found.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have