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Start Over Creator Boček, J.

1. Reversible and irreversible changes of fluorescence parameters during photoinhibítion in the Synechococcus elongatus cells

Creator:
J., Masojídek, J., Boček, J., and Prášil, O.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
A decrease of F,„ followed with a ceitain delay by an increase of was detected in the cells of Synechococcus elongatus in the first 120 min of the photoinhibitory treatment at 56 <>0 (growth temperature). Then F,n started to rise in parallel with F,, and this process proceeded widi the same rate both in the light and in the dark at 56 °C after light treatment. On tíie contrary, an increase of F^ observed during the light treatment at 15 °C was largely reversed after subsequent transfer of the ceUs to the dark at 56 <>€ but F,q remained nearly unchanged during the dark incubation.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Two mechanisins of photosystem 2 photoinactivation: do they exist in vivo?

Creator:
Komenda, J., Masojídek, J., Prášil, O., and Boček, J.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
High (HI, 200 W m'^) and low (LI, 30 W m"^) irradiance treatments on the cells of cyanobactenum Synechococcus elongatus Nfig., var. thermalis Geitl. strain KOVROV 1972/8 were perfonned in the presence of chloramphenicol (CAP), and with addition of DCMU and hydroxylamine (HA), respectively, at growth (56 °C) and low (20 °C) temperatures, to distínguish allegedly different mechanisms of PS 2 photoinactivation (PS 2 PI). At both temperatures HI caused a decline of Fy and Hill reaction activity (HRA) followed by degradation of Dl and to a lesser extent also D2 protein. Fq increased slowly during irradiance at 56 while at 20 ®C it quickly rose to constant level. Degradation of proteins was slowed at a lower temperature. The presence of DCMU during photoinhibition significantly blocked the Fq rise and also prevented PS 2 protein degradation at both temperatures. The course of PS 2 PI under LI resembled tlmt, observed at HI, but changes were much slower. During irradiation of the cells, in which oxygen evolving complex (OEC) was impaired by HA, we observed: (/) at least a ten-fold faster decline of PS 2 electron transport activity than in the cells vňth fimctional OEC under the same conditions; (2) an extensive degradation not only of Dl and D2, but also of the apoprotein of chlorophyll-protein CP43 {ACP43y, (3) almost complete inhibition of PS 2 protein degradation in the presence of DCMU. Thus under all conditions tested in vivo which do not affect the fimction of OEC, the fimction of OEC, PS 2 PI proceeds via the acceptor side and a fimctional impairment of OEC is necessary for induction of the donor side mechanism. When OEC is impaired (e.g. by HA) this mechanism can come in action.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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