title: 515 nm Absorption changes in Chlorella at short times (4--100 mus) after a flash.
abstract: Using Chlorella, three types of absorption changes at 515 nm have been studied in the 4-100 mus time range following a flash. (1) The absorption change observed when both photoreactions are blocked, probably due to the formation of the triplet state of a carotenoid, is show to depend on Photosystem II excitation only. (2) The absorption increase induced by photoreaction I is biphasic; first phase, complete in less than 4 mus, followed by a slower phase with a half-rise time of 15-20 mus. (3) On the other hand, photoreaction II induces only a fast absorption increase (lessthan 4 mus). The time course of the biphasic 515 nm absorption increase induced by photoreaction I is similar to the biphasic absorption decrease previously observed at 480 nm by Cox and Delosme (1976, C.R. Acad. Sci. Paris 282D, 775-778). No significant absorption change is observed at 490 nm. These results suggest that the transmembrane electric field induced by photoreaction I rises to its maximum value in at least two phases within 100 mus following flash excitation.
mesh_terms: D002708:Chlorella / Q000187:drug effects / Q000378:metabolism*; D004237:Diuron / Q000494:pharmacology; D006898:Hydroxylamines / Q000494:pharmacology; D007700:Kinetics; D008027:Light; D010788:Photosynthesis / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D006898:Hydroxylamines; D004237:Diuron