
%0 Journal Article
%A Chow, WS 
%A Hope, AB 
%T The Stoichiometries of Supramolecular Complexes in Thylakoid Membranes From Spinach Chloroplasts
%J Functional Plant Biology
%D 1987/02/01
%V 14
%N 1
%P 21-28
%K 
%R https://doi.org/10.1071/PP9870021
%U https://www.publish.csiro.au/paper/PP9870021 
%X The concentrations of photosystem II (PS II), photosystem I (PS I) and cytochrome b/f complexes on a chlorophyll basis have been determined for chloroplasts of spinach grown under three irradiances in a glasshouse. Assaying PS II by atrazine binding gave concentrations that exceeded the estimates from flash-induced O2 or H+ yield by a factor of 1.21 ± 0.04 (23). Since part of this factor (1.14) is expected to arise from missed turnovers in excited reaction centres, it is concluded that both methods are valid to determine [PS II] in gently isolated chloroplasts. The agreement between the methods also suggests that atrazine does not bind to additional sites of quenchers such as 'Q400', contrary to the suggestion of R. J. Dennenberg and P. A. Jursinic [Biochim. Biophys. Acta 808 (1985), 192-200].    Whilst [PS I] was independent of growth irradiances, [PS II] and [cyt f ] increased with irradiance, as did the latent ATPase activity, a measure of the concentration of coupling factor 1. If [PS I] is taken as constant at 1.65 mmol (mol Chl)-1, the mean stoichiometries of PS II : cyt b/f complex : PS I obtained at the minimum and maximum irradiances were 1.2 : 0.7 : 1 and 1.6 : 1.0 : 1 respectively, PS II being determined by atrazine binding. 
