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Start Over Subject photochemical activities

1. Diurnal fluctuations in photochemical activities of chloroplasts in field grown Cyamopsis tetragonoloba seedlings

Creator:
Lingakumar, K. and Kulandaivelu, G.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence, photochemical activities, and photosystems 1 and 2
Language:
Multiple languages
Description:
In field-grown Cyamopsis seedlings, distinct changes were found in the rates of photosystems (PS) 2 and 1 activities at different time of the day. Maximum PS2 activity was at around 11:00 h and decreased thereafter. On the contrary, PS1 activity continued to increase up to 14:00 h and declined in evening hours. Significant energy transfer from PS2 to PS1 was evident during the morning and evening hours of the day whereas a slow excitation of PS2 and energy transfer was favoured during noon hours. and K. Lingakumar, G. Kulandaivelu.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Response of intact cyanobacterial cells and their photosynthetic apparatus to Cd2+ ion treatment

Creator:
Tůmová, E. and Sofrová, D.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll, dodecylmaltoside, heavy metals, photochemical activities, photosynthetic pigment content, photosystems 1 and 2, Synechococcus, and toxic metals
Language:
Multiple languages
Description:
Intact cells of Synechococcus elongatus were treated with different concentrations (0.1 and 1.0 mM = Cd0.1, Cd1.0) of CdCl2 for 24 h. Cd0.1 treatment stimulated growth of the cell culture and chlorophyll (Chl) a concentration in the culture. Cd1.0 inhibited both the above mentioned parameters. The oxygen evolving activity of intact cells (H2O → BQ) as well as of isolated thylakoid membranes, TM (H2O → DCPIP; H2O → PBQ + FeCy) decreased after 24 h of Cd1.0 cultivation to 7 %. Photosystem 1 (PS1) activity was less sensitive to the effect of Cd2+ than PS2 activity. CdCl2 concentration in cultivation media after 24 h of cultivation proved that the cyanobacterium cells take up these ions to a large extent from the cultivation medium. After 24 h of the Cd1.0 treatment only 12 % of the amount of Cd2+ originally added to the cultivation medium was found. The ratio of external-antenna pigments, phycocyanin, and allophycocyanin to Chl increased approximately twofold with growing Cd2+ concentration in the cultivation medium. This ratio was found in both TM and dodecylmaltoside extracts. and E. Tůmová, D. Sofrová.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. The influence of increased solar UV-B radiation on magnesium-deficient cowpea seedlings: Changes in the photosynthetic characteristics

Creator:
Premkumar, A. and Kulandaivelu, G.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll, chlorophyll fluorescence, induction, chloroplast proteins, CO2 uptake, net photosynthetic rate, photochemical activities, and Vigna unguiculata
Language:
Multiple languages
Description:
The influence of increased solar UV-B radiation on the photosynthetic characteristics in cowpea seedlings (Vigna unguiculata) grown at optimal (Mgs) and low (Mgd) Mg levels were studied. Both higher UV-B and Mgd treatments caused significant drops of photochemical activities and net CO2 uptake rates (PN). Yet the UV-B-induced decrease in the photosynthetic efficiency was lesser in Mgd seedlings. The leaf Chl a fluorescence measurements proved that after receiving an enhanced UV-B radiation these seedlings showed a significant enhancement in their variable parts. The PSM oscillation of slow fluorescence kinetics was remarkably altered by both treatments. The PN also followed a typical inhibitory pattern as seen in photochemical activities. Concentrations of several chloroplast proteins in trifoliate leaves were significantly reduced by Mgd treatment and unaffected by the other two treatments. Whereas the contents of 43-47 kDa polypeptides in primary leaves were markedly reduced with a maximal effect in Mgd seedlings, no major difference was noted for combined stress. and A. Premkumar, G. Kulandaivelu.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public