EFFECTS OF BICARBONATE ION ON CHLOROPHYLL a FLUORESCENCE TRANSIENTS AND DELAYED LIGHT EMISSION FROM MAIZE CHLOROPLASTS

Abstract

Abstract-Using high-intensity actinic light, the chlorophyll a fluorescence transient from HC0,--depleted chloroplasts shows a rapid initial rise (0 + 1) followed by a slow phase ( I + P). In the presence of HC0,-, the 0 -+

The Effect of Bicarbonate on Photosynthetic Oxygen Evolution in Flashing Light in Chloroplast Fragments

“…The first interpretation, as mentioned in the introduction, is inconsistent with our previous work (1)(2)(3) Meanwhile, it appears reasonable to consider how HCO3-is influencing the oxygen-evolving mechanism.…”

“…Electron flow from the artificial electron donor diphenyl carbazide to dichlorophenolindophenol via PS II is insensitive to HCO3- (1). Effects of HCO3-on chlorophyll (Chl) a fluorescence transients and on delayed light emission in the 0.5-to 5-sec time period also seem to suggest a site of action of HCO3v on the oxygen-evolving side of PS II (2). This latter work led Stemler and Govindjee (2) Sn+1, where n = 0, 1, or 2) after a photoact.…”

“…Effects of HCO3-on chlorophyll (Chl) a fluorescence transients and on delayed light emission in the 0.5-to 5-sec time period also seem to suggest a site of action of HCO3v on the oxygen-evolving side of PS II (2). This latter work led Stemler and Govindjee (2) Sn+1, where n = 0, 1, or 2) after a photoact. The final oxygenevolving reaction (S4 + 02 precursor(s) --O + So), however, appears to be independent of HCO3-.…”

“…Recent investigation of the role of HCO3-in the Hill reaction indicates that this ion plays a critical role in the oxygenevolving mechanism (1)(2)(3). Evidence is available that strongly suggests that HCO3-acts on the oxygen-evolving side of photosystem (PS) II.…”

EPR measurements on the effects of bicarbonate and triazine resistance on the acceptor side of Photosystem II

“…This signal (split + To whom correspondence should be addressed It is known that absence of CO2 (in the presence of formate) leads to a blockage of electron flow between QA and the plastoquinone pool [lo], whereas steady-state electron flow from Hz0 to QA does not appear to be impaired [11,12]. However, the QA oxidation by the water splitting system is slowed down in the absence of HCOp [13,14], whereas also the oxidation of QA by the oneelectron acceptor C400 [15] was interpreted to be blocked in the absence of HCO; [16], although this interpretation was questioned recently [ 171. In addition, COZ, and probably also the redox state of QA, can modulate herbicide affinity [12,18,19].…”