Bundle sheath and mesophyll chloroplasts from Zea mays showed comparable rates of O(2) evolution, which amounted to about half of the rate observed in spinach (Spinacia oleracea) chloroplasts.Ratios of 4.5, 4.6, and 6.2 Mn(2+) atoms per 400 chlorophylls were observed in mesophyll, bundle sheath, and spinach chloroplasts, respectively. These ratios roughly correspond to the observed O(2) evoluti...

The cyanobacterial cytochrome b(6)f complex is central for the coordination of photosynthetic and respiratory electron transport and also for the balance between linear and cyclic electron transport. The development of a purification strategy for a highly active dimeric b(6)f complex from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 enabled characterization of the structur...

Absorbance changes in the 520nm region have been interpreted as indicating an electrochromic response of pigment molecules to the electric field formed across the membrane by the primary charge separation of the two chloroplast photoreactions, Photosystem I and I1 (Junge & Witt, 1968; Wolff et al., 1969). We have measured the flash-induced 518nm absorbance change in chloroplasts as a function o...

The effects of disalicylidenepropanediamine (DSPD) and disulfo-disalicylidenepropanediamine (sulfo-DSPD) on the photosynthetic electron transport of isolated chloroplasts have been reexamined.Our data suggest that DSPD, but not sulfo-DSPD, is an effective inhibitor of electron transport between photosystem II and photosystem I before or at plastocyanin. Furthermore, both DSPD and sulfo-DSPD blo...

Pseudomonas syringae pv. tabaci (Pst) is a hemibiotrophic bacterial pathogen responsible for tobacco wildfire disease. Although considerable research has been conducted on the tobacco plant's tolerance to Pst, the role of light in the responses of the photosystems to Pst infection is poorly understood. This study aimed to elucidate the underlying mechanisms of the reduced photosystem damage in ...

A comparison of the quantum yield spectra of the oxygenic (H(2)O as the electron donor) with the anoxygenic (H(2)S as the electron donor) photosynthesis of the cyanobacterium, Oscillatoria limnetica reveals that anoxygenic photosynthesis is driven by photosystem I only. The highest quantum yields of the latter (maximum; 0.059 CO(2) molecules/quantum of absorbed light) were obtained with wavelen...

A mild tryptic digestion of chloroplast membranes eliminates the effects of saturating concentrations of cations (3 to 5 millimolar MgCl(2)) on chlorophyll fluorescence yield, membrane stacking, and photosystem II photochemical efficiency in spinach. At the same time, the negative surface potential of the membranes is increased (by trypsin) as revealed by studies with 9-aminoacridine. High conc...

Nonsaturating light at 600 or 436 nanometers was used to excite specifically phycocyanin or chlorophyll a, respectively, both of which participate in light capture in photosystem II of Cyanidium caldarium. The ratio of absorption of light by phycocyanin to chlorophyll in photosystem II in this organism is >20 at 600 nanometers and </=0.2 at 436 nanometers.The distribution of the absorbed light ...

We compare the chlorophyll fluorescence decay kinetics of the wild type and the D2-H117N mutant photosystem II reaction centers isolated from Chlamydomonas reinhardtii. The histidine residue located at site 117 on the D2 polypeptide of photosystem II is a proposed binding site for one of two peripheral accessory chlorophylls located in the reaction center complex. The peripheral accessory chlor...

Detergent effect on Cytochrome b559 from spinach photosystem II was studied by electron paramagnetic resonance (EPR) spectroscopy in D1-D2-Cyt b559 complex preparations. Various n-dodecyl-β-D-maltoside concentrations from 0 to 0.2% (w/v) were used to stabilise the D1-D2-Cyt b559 complexes. Low spin heme EPR spectra were obtained but gz feature positions changed depending on detergent conditions...