Photosynthetic processes, interference

The effect was used to detect traces of oxygen [103, 104) produced in the photosynthetic process. TTypaflavine, benzoflavine, Euchrysine 3R, Rheonine 3 A, Rhoduline Yellow, safranine, chlorophyll, and hematoporphyrin adsorbed on silica gel or aluminium oxide were the dyes that were most efficiently quenched. Unfortunately, most dyes are photolabile, and traces of water or ammonia strongly interfere. Hydrogen, nitrogen, methane, ethylene, and carbon dioxide are without influence. The method is suitable for the extremely sensitive determination of oxygen at partial pressures between O.S and 0.006 kPa and is characterized by a fast response tim but requires several seconds for regeneration. 

Table III. Influence of herbicides that interfere with photosynthetic processes on growth and multiplication of Chlamydomonas reinhardii. The algae were kept in a synchronized 12/12 h light/dark cycle, with Oh at the beginning of a dark phase.

The first generation of urea herbicides is represented by types such as monuron and linuron (see Table 29.12). These compounds in general interfere with the photosynthetic process, as they inhibit electron transport in the photosystem II process of the plant. They have varying degrees of selectivity, depending upon the structure. Some owe their selectivity to physical properties such as water solubility and soil absorption. If the crop is a deep-rooted perennial, the shallow rooted annual weeds are controlled by using a herbicide that is not easily leached down into the root zone... 

Arnon and his collaborators (11,15) have reported that whole spinach chloroplasts, prepared in 0.5 M glucose or 0.35 M NaCl, are able to carry out not only the Hill reaction (f.c., the photolysis of water in the presence of artificial hydrogen acceptors) but also photosynthetic phosphorylation and carbon dioxide fixation. Both these processes are light-dependent and strongly inhibited by o-phenanthroline, which interferes with the photochemical reaction. Their early results are shown in Table V. These important findings... 

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