Photosynthetic mechanism

Studies (see, e.g., (101)) indicate that photosynthesis originated after the development of respiratory electron transfer pathways (99, 143). The photosynthetic reaction center, in this scenario, would have been created in order to enhance the efficiency of the already existing electron transport chains, that is, by adding a light-driven cycle around the cytochrome be complex. The Rieske protein as the key subunit in cytochrome be complexes would in this picture have contributed the first iron-sulfur center involved in photosynthetic mechanisms (since on the basis of the present data, it seems likely to us that the first photosynthetic RC resembled RCII, i.e., was devoid of iron—sulfur clusters). 

Govindjee, Photosynthetic Mechanisms of Green Plants, NAS-NRC Publication 1145, Washington, D.C. (1963). 

Under European conditions water requirements are typically in the range of 200-800 g water per gram dry matter (DM) produced (Table 5.6). Determined by genetic characteristics, water consumption of C4 crops is less than that of C3 crops, although a wide variation exists between the plant species due to certain photosynthetic mechanisms. 

Light-driven electron transfer in plant chloroplasts during photosynthesis is accomplished by multienzyme systems in the thylakoid membrane. Our current picture of photosynthetic mechanisms is a composite, drawn from studies of plant chloroplasts and a variety of bacteria and algae. Determination of the molecular structures of bacterial photosynthetic complexes (by x-ray crystallography) has given us a much improved understanding of the molecular events in photosynthesis in general. 

A group of substituted ureas used as herbicides has a profound inhibiting effect on the photosynthetic mechanism in plants. The relatively advanced... 

Malstrom and Neilands (68). The recent reviews of San Pietro and Black (86) and Arnon (6) are more specifically concerned with ferredoxin in photosynthesis. Also pertinent to the general subject of ferredoxin are the symposia on photosynthesis in higher plants (Photosynthetic Mechanisms of Green Plants (82)) and on the role of non-heme iron proteins in energy conversion (San Pietro (55)). 

Nobel, P.S., and Walker, D.B. 1985. Structure of leaf photo synthetic tissue. In Barber, J., and Baker, N.R. (Eds.), Photosynthetic Mechanisms and the Environment. Elsevier, Amsterdam, pp. 501-536. 

Arnold W, Oppenheimer JR. Internal conversion in the photosynthetic mechanism of blue-green algae. J. Gen. Physiol. 1950 33 423-435. 

Photosynthesis begins with the transfer of COj into the cell from the atmosphere or water. Photosynthetic enzymes then transfer the inorganic carbon to a 5-carbon organic compound to form two 3-carbon carboxylic acid molecules. (This is the case for the C3 photosynthetic mechanism.) In these steps, reaction of occurs slightly faster than... 

Fig. 11-8. Net primary productivity (NPP) typified response of plants to changes in the atmospheric C02 concentration. [Adapted from Berry (1975).] C3 and C4 plants differ in their photosynthetic mechanism. The former generate a three-carbon carboxylic acid (phosphogly-ceric acid) as the first identifiable photosynthetic product the latter form first a four-carbon dicarboxylic acid (oxaloacetic acid) see Devlin and Barker (1971) for details. Examples for C4 plants are tropical grasses such as maize, sorghum, and sugar cane. All forest species are C3 plants.

Fig. 2. Franck Condon principle as applied to carotenoids. The photograph of James Franck, the co-di scoverer of the principle is shown as an inset, and was taken by the author in 1963 when Franck attended the Airlie House Conference on Photosynthetic Mechanisms of Green Plants, organized by Bessel Kok and Andre Jagendorf.

The primary quantum conversion act of photosynthesis in chemical terms is an ionization occurring in a charge transfer complex (28). But this cannot occur in isolated charge transfer molecules in solution or in a homogeneous single phase crystal because the products cannot escape from each other. The primary quantum conversion act as it occurs in modern photosynthesis can only take place in a laminated structure where the electrons and holes can escape from each other by electron migrations and not by atomic migrations (74). (For a discussion of the evolution of photosynthetic mechanisms, see Calvin, 74). 

Infrared gas analyzers have been used to record differential ppm levels of CO2 and water vapor in the study of photosynthetic mechanisms in investigations of plant growth, and COj has been monitored in the effluent air from bacterial cultures. 

Whittingham, C. P., Hiller, R. G., and Bermingham, M. (1963). In Photosynthetic Mechanisms in Green Plants, Publ. No. 1145, pp. 675-683. National Academy of Sciences, National Research Council, Washington, D.C. 

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