The influence of cytochrome b559 on the fluorescence yield of chloroplasts at low temperature

The Primary Reaction of Plant Photosystem Ii

“…The C-550 absorbance change can be restored by adding 8-carotene to the extracted chloroplasts as had been previously demonstrated (Okayama and Butler, 1972b;Cox and Bendall, 1974;Knaff et a!., 1977). Consideration of this requirement for 8-carotene, the existence of carotenoid electrochromic bandshifts in photosynthetic bacteria, and the absence of any evidence to support a direct role for 8-carotene in Photosystem I1 primary photochemistry made it seem even more likely that the C-550 absorbance change resulted from an electrochromic band-shift rather than from the primary acceptor itself.…”

“…These initial observations were confirmed and extended in several laboratories (Erixon and Butler, 1971a and b;Boardman et al, 1971;Kitajama and Butler, 1973;Wessels et al, 1973). It now appears that both the high potential (Em = +350mV) from (Knaff and Arnon, 1971 ;Boardman et al, 1971;Okayama and Butler, 1972b) and low potential (Em = +50mV) from (Wessels et al, 1973) of the cytochrome can be oxidized at liquid nitrogen temperature. As the temperature is raised above 77 K, the extent of cytochrome b559 photooxidation decreases.…”

Chlorophyll a fluorescence induction: a personal perspective of the thermal phase, the J–I–P rise

“…(1) P680 ? can quench Chl a fluorescence as efficiently as Q A (Okayama and Butler 1972;Butler et al 1973;Shinkarev and Govindjee 1993;Bruce et al 1997; for a different opinion regarding P680 ? efficiency as a quencher, see Steffen et al 2005).…”

Modification of oxygen evolving center by Tris-washing

“…Regarding to the variable fluorescence of Tris-washed chloroplasts, Butler [56] stated, that under steady irradiation the fluorescence yield of Tris-washed chloroplasts increased very little because there were not sufficient endogenous electron donors to reduce the pools of redox compounds (PQ) which could oxidize C550 (Q), and that in the presence of DCMU, which blocked electron transport immediately after C550 (Q), the fluorescence yield did increase to its maximal level during irradiation showing that endogenous donor was able to reduce C550 (Q). The other quencher "P680 +'', whose effect was noticed by Okayama and Butler [120], Butler [121] and Butler et al [122], also decreased the variable fluorescence yield of Tris-washed chloroplasts excited by repetitive flashes in the rate of ~ 1HZ [64]. In this condition, z+-P680+-Q -was rapidly built up and the fluorescence was quenched even in the presence of Q-.…”