The mechanisms of photosynthetic electron transport can be elucidated by inhibition of electron flow through the use of specific substances that, when combined with the chlorophyll chlorophyll a fluorescence emission was measured to investigate the effect of several inhibitors of the photosynthetic electron transport chain in canola leaf discs. Leaf discs were incubated in the dark for 2 hours ...

The light activation mechanism of the latent H(+)-ATPase was investigated in intact spinach (Spinacia oleracea, Hybrid 424) chloroplasts. The following observations were made. (a) Photosystem I electron acceptors such as methyl viologen, nitrite, oxaloacetate, etc., inhibit the light activation of the enzyme. (b) The electron transfer inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) ful...

The inhibition of photosynthetic electron flow in broken chloroplasts by dibromothymoquinone and dibromothymohydroquinone (DBMIBH2) is reversed by dithiothreitol (DTT) as well as by serum albumin. The reversal of DBMIBH2 inhibition by DTT shows a time lag, that of DBMIB only, when chloroplasts and DBMIB had been preilluminated. This is to show that chloroplasts reduce DBMIB and that probably DB...

Alkyl substituted 2-halogen-4-nitro-phenols (like bromonitrothymol) are potent inhibitors of photosynthetic electron flow in chloroplasts. There inhibition site is identical to that of DCMU, though the phenols do not contain their essential chemical element responsible for inhibition nor do they follow their correlation of chemical structure and biochemical function. Binding of labelled metribu...

Nitrogen fixation, as measured by acetylene reduct~on, has been detected to be associated with various hermatypic corals. Experiments were carried out on the massive coral Favia f a v u s both in situ and in the laboratory. Nitrogen fixation activity was found to be light dependent and fully inhibited by 5 X 10-6 M DCMU [3-(3,4-dichloropheny1)-1,l-dimethylurea Addition of glucose restored nitro...

Herbicide application incurs water contamination and thus effective herbicide detection methods are needed. In this research, a kinetic model was developed to describe the processes of herbicide diffusion into plant tissues and binding to the active sites. DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea], a commonly used herbicide, was used as a test chemical and its diffusion into plant leaves a...

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 -+ I rise is delayed but the I + P phase is much more rapid. Using lowintensity actinic light, the chlorophyll a fluorescence transient from 3-(3.4-dichlorophenyI)I , I dimethylurea (DCM...

The artificial electron donor compounds p-phenylenediamine (PD). N, N, N', N'tetramethyl-p-phenylenediamine (TMPD), and 2,6-dichlorophenol-indophenol (DCPIP) restored the Hill reaction and photophosphorylation in chloroplasts that had been inhibited by washing with 0.8 M tris (hydroxymethyl)aminomethane (tris) buffer, pH 8.0. The tris-wash treatment inhibited the electron transport chain betwee...

Chloroplastic phosphofructokinase, phosphorylase, phosphoglucomutase, and phosphoglucoisomerase in peas are light inactivated. The effect of light on phosphofructokinase is mimicked by dithiothreitol. DCMU, arsenite, and sulfite inhibit light modulation of the enzyme. No effect of light inactivation on the K(m) (fructose-6-P) or pH optima of phosphofructokinase was observed.