Kinetics of Action of Different Photosystem II Herbicides on Thylakoids

1990 ◽  
Vol 45 (5) ◽  
pp. 348-352 ◽  
Author(s):  
Jean-Marc Ducruet ◽  
Sophie Creuzet ◽  
Josiane Viénot
Keyword(s):  
Electron Transfer ◽  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
Temperature Dependent ◽  
Binding Process ◽  
Uracil Derivatives ◽  
Fluorescence Measurements ◽  
Kinetics Of

The kinctics of inhibition of photosystem II electron transfer by different diuron-like herbicides (ureas, triazines, triazinoncs, biscarbamates. uraciles) were studied, mainly by chlorophyll fluorescence measurements. Uracil derivatives and cyanazine, a particular triazinc. were the slowest acting compounds. The half-times of action were strongly temperature-dependent and were of the order of tens of seconds at 5 °C for urea or triazine inhibitors. The role of different limiting steps in the binding process is discussed.

Kinetics of Electron Transfer from QAto QBin Photosystem II†

Biochemistry ◽  
2001 ◽  
Vol 40 (39) ◽  
pp. 11912-11922 ◽  
Author(s):  
Rik de Wijn ◽  
Hans J. van Gorkom
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Kinetics Of

Voltammetric investigation of the kinetics of alkali metal cation reduction in N,N-dimethylformamide

1975 ◽  
Vol 28 (2) ◽  
pp. 237 ◽  
Author(s):  
JW Diggle ◽  
AJ Parker ◽  
DA Owensby
Keyword(s):  
Electron Transfer ◽  
Alkali Metal ◽  
Propylene Carbonate ◽  
Rate Constant ◽  
Alkali Metal Cation ◽  
Electrode Reaction ◽  
Amalgam Electrode ◽  
Kinetics Of ◽  
Dipolar Aprotic Solvents

The standard electron-transfer heterogeneous rate constant of lithium, potassium, sodium and caesium amalgams in N,N-dimethylformamide was ascertained employing cyclic voltammetry in an effort to relate the presence of a non-equilibrium electrode reaction at the dropping lithium amalgam electrode to the variation of the lithium amalgam electrode potential with amalgam electrode con- figuration, i.e. whether streaming, dropping or stationary. Such variations are not observed at other alkali metal amalgam electrodes. ��� In the dipolar aprotic solvents the standard electron-transfer heterogeneous rate constant for the Li(Hg) electrode increases as the solvating power for Li+ decreases, i.e. dimethyl sulphoxide < di- methylformamide < propylene carbonate. Water is a much stronger solvator of Li+ than is propylene carbonate, but the electron transfer is faster in water than in propylene carbonate; the important role of entropic contributions in ion solvation is discussed as an explanation.

scholarly journals Two Quenchers Formed During Photodamage of Phostosystem II and The Role of One Quencher in Preemptive Photoprotection

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alonso Zavafer ◽  
Ievgeniia Iermak ◽  
Mun Hon Cheah ◽  
Wah Soon Chow
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosystem Ii ◽  
Time Course ◽  
Physiological Role ◽  
Reaction Centre ◽  
Time Resolved ◽  
Fluorescence Quencher

AbstractThe quenching of chlorophyll fluorescence caused by photodamage of Photosystem II (qI) is a well recognized phenomenon, where the nature and physiological role of which are still debatable. Paradoxically, photodamage to the reaction centre of Photosystem II is supposed to be alleviated by excitation quenching mechanisms which manifest as fluorescence quenchers. Here we investigated the time course of PSII photodamage in vivo and in vitro and that of picosecond time-resolved chlorophyll fluorescence (quencher formation). Two long-lived fluorescence quenching processes during photodamage were observed and were formed at different speeds. The slow-developing quenching process exhibited a time course similar to that of the accumulation of photodamaged PSII, while the fast-developing process took place faster than the light-induced PSII damage. We attribute the slow process to the accumulation of photodamaged PSII and the fast process to an independent quenching mechanism that precedes PSII photodamage and that alleviates the inactivation of the PSII reaction centre.

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