The influence of u.v. radiation on the kinetics of the photo-induced conversions of the reaction centre P700 in isolated bean chloroplasts and subchloroplast particles of the photosystem II (p.s. II) of pea leaves has been studied. It is shown that this radiation does not affect the value of the e.s.r. I signal from P700+ induced by far red light (λmax = 707 nm) exciting mostly photosystem I. It was found that u.v. radiation suppresses the photochemical activity of p.s. II and, thereby, lowers the flux of electrons between the photosystems with release of Mn2+ ions from the membrane and change in the form of the e.s.r. II, signal belonging to the tyrosine radicals of p.s. II. Evidence has been obtained on the existence of several targets in p.s. II varying in sensitivity to the action of radiation. It is assumed that the first to be damaged is the manganese complex of the system of decomposition of water.
|Number of pages||4|
|Publication status||Published - Dec 1 1992|
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