Carbon dioxide dark fixation

Zabka,G.G., Chaturvedi,S.N. Water conservation in Kalanchoe blossfeldiana in relation to carbon dioxide dark fixation. Plant Physiol. 55, 532-535 (1975)... 

The fixation of carbon dioxide to form hexose, the dark reactions of photosynthesis, requires considerable energy. The overall stoichiometry of this process (Eq. 22.3) involves 12 NADPH and 18 ATP. To generate 12 equivalents of NADPH necessitates the consumption of 48 Einsteins of light, minimally 170 kj each. However, if the preceding ratio of l ATP per NADPH were correct, insufficient ATP for COg fixation would be produced. Six additional Einsteins would provide the necessary two additional ATP. Prom 54 Einsteins, or 9180 kJ, one mole of hexose would be synthesized. The standard free energy change, AG°, for hexose formation from carbon dioxide and water (the exact reverse of cellular respiration) is +2870 kj/mol. 

Ozone causes both quantitative and qualitative changes in carbon dioxide fixation patterns. Wilkinson and Bames, using carbon dioxide-found a reduction in radioactivity in soluble sugars and increases in free amino acids and sugar phosphates in white pine after a 10-min exposure to ozone at 0.10 ppm. Miller observed a decrease in carbon dioxide-fixation in ponderosa pines that correlated with loss of chlorophyll, after exposure to ozone at 0.30-0.35 ppm. The Hill reaction rates of chloroplasts isolated from healthy and ozone-injured ponderosa pine indicated that both light and dark reactions of the chloroplasts from ozone-injured plants were depressed. Barnes found depressed photosynthesis and stimulated respiration in seedlings of four pine species of the southeastern United States after exposure to ozone at 0.15 ppm. 

The dark reaction involves the fixation of carbon dioxide to form carbohydrates. The ATP and the NADPH produced in the light reaction drive this carbon fixation. It might be thought that the interruption of the Calvin cycle would also produce effective herbicides but this is not the case. There are two reasons why. First, the reaction is not an energetic reaction whose interruption would lead to the destruction of cellular components and second, the enzymes involved in the process are present in very high amounts. If an enzyme is to be targeted as a key step in the metabolism of a plant, it is important that it is present in small amounts and that it is not turned over very quickly. If an enzyme is abundant,... 

The photosynthetic block precedes sucrose synthesis, and sucrose partially reverses the inhibition caused by the lack of fixation of carbon dioxide. D-Fructose disappears first, after treatment, followed by sucrose, and then u-glucose.188 It is likely that other metabolic systems are involved as well, since the amino acid distributions were not identical to the I4C02 dark-fixation products.189 Uptake of sucrose-14C increased some acids (as-... 

Photosynthesis uses solar energy to synthesize carbohydrate from carbon dioxide and water. In the light reactions, the light energy drives the synthesis of NADPH and ATP. In the dark reactions (carbon-fixation reactions), the NADPH and ATP are used to synthesize carbohydrate from C02 and H20. 

The dark reactions (carbon-fixation reactions) use the ATP and NADPH produced by the light reactions to fix carbon dioxide as carbohydrate sucrose and starch. The reactions form a cycle (the Calvin cycle) in which the enzyme ribulose bisphosphate carboxylase (rubisco), located in the stroma, condenses a C02 molecule with ribulose 1,5-bisphosphate to produce two molecules of 3-phosphoglycerate. Other reactions then regenerate the ribulose... 

The dark reactions (also called the carbon-fixation reactions) use the ATP and NADPH produced by the light reactions to convert carbon dioxide into carbohydrate. The final products are sucrose and starch. 

Starvation. The early reports that Hill inhibitors limited photosynthesis and that starch disappeared from treated plants, prompted some investigators to refer to these compounds as photosynthesis inhibitors. Photosynthesis is inhibited because ATP and NADFH are not available for carbon dioxide fixation. However, there is little evidence that the plants starve to death. If this were the only process affected, phytotoxic symptoms should resemble those that appear on plants kept in total darkness. Deficiency of photosynthate does limit new growth, but does not account for the morphological alterations that occur within a few hours after treatment. The mechanisms that lead to phytotoxicity appear to be considerably more complex than would result from limiting carbohydrate synthesis by suppression of carbon dioxide fixation (2). ... 

The dark reaction, known as the Calvin cycle, uses the reducing power of NADPH as well as the free energy stored in the ATP to assimilate carbon dioxide in the form of carbohydrates. The way by which Nature achieves carbon fixation is via the reaction of CO2 with ribulosebiphosphate (RuBP) to give two molecules of 3-phosphoglycerate, a process which is catalyzed by the enzyme RuBP-carboxylase. The phosphogylcerate is converted further to fructose 6-phosphate, the final product of the Calvin cycle. The overall reaction, despite its complex mechanism, corresponds to the simple Eq. (16) above. 

Carbon dioxide is also fixed in the dark by photosynthetic organisms by the so-called Wood-Werkman reaction (Wood and Stjemholm, 1962). The CO2 assimilated, however, rarely exceeds that formed by dark respiration i.e. there is no net CO2 uptake. On the other hand, the amount of organic carbon derived from CO2 may be as high as 30% in heterotrophic bacteria and 90% in mixotrophic organisms. In the natural environment, non-photo-synthetic CO2 fixation by these organisms, together with the above-mentioned dark fixation by photosynthetic organisms, may under some condi-... 

Let us return to the so-called dark reaction of photosynthesis. In it, both the NADPH2 and the ATP formed in the light reactions are consumed in the fixation of C02. The fixation reactions were charted by Melvin Calvin and his co-workers in Berkeley, California (for which Calvin received the Nobel Prize for 1961), with the use of radioactive carbon dioxide. During these reactions, C02 is made to combine with a pentose (5-carbon) sugar, ribulose diphosphate, to give an unstable 6-carbon intermediate which breaks down to two molecules of the 3-carbon phosphoglyceric acid. 

The reactions of the Calvin cycle, which is the process of carbon dioxide fixation in plants (also known as the dark cycle), are listed below ... 

In the dark reactions of photosynthesis, the fixation of carbon dioxide takes place when the key intermediate ribulose-1,5-fo iphosphate reacts with carbon dioxide to produce two molecules of 3-phosphoglycerate. This reaction is catalyzed by the enzyme ribulose-l,5-feq3hosphate carboxylase/oxygenase (rubisco), one of the most abundant proteins in nature. The remainder of the dark reaction is the regeneration of ribulose-1,5-fo iphosphate in the Galvin cycle. 

Carbon dioxide fixation by flax cotyledons measured by an IRGA with illumination of 115 Wm , previously incubated with 10 % monuron in the dark or light of 5.25 or 30 Wm , from Pallett... 

The soluble proteins left in the supernatant after the centrifugation appeared to include most of the enzymes required for CO2 fixation during photosynthesis. By themselves, they were capable of very little fixation and reduction of carbon dioxide. However, when the particulate green material obtained by sedimentation was recombined with the soluble proteins and illuminated in the presence of radioactive carbon dioxide, a significant amount of fixation of carbon dioxide and form.ation of reduced carbon compounds was observed. Thus, the separation of light and dark phases of photosynthesis (predicted by Van Niel and confirmed by the experiments of Hill and Ruben) was demonstrated in terms of the physical separation of the light and dark biochemical machinery. 

Photosynthetic earboxylation the enzymatic fixation of carbon dioxide in photosynthesis. In C-3 plants, the photosynthetic earboxylation enzyme is ri-bulose iirphosphate carboxylase (EC 4.1.1.39). In C-4 plants it is phosphoeno/pyruvate carboxylase (EC 41.1.31). P. c. is the first step of carbon dioxide assimilation in photosynthesis, and one of the dark reactions. 

As shown in Chapter 3 (see also Fig. 5.1), in most cases dark CO2 fixation in CAM means net fixation of atmospheric carbon dioxide. However, this statement does not exclude that endogenously produced CO2 (respiratory CO2) may also serve as the substrate for dark CO2 fixation. In special cases, mainly under the influence of environmental factors, endogenously produced CO2 may provide the only source for dark CO2 fixation and malic acid synthesis (cf. Chap. 6.2.2.1). 

Pfeffer s interpretation of CAM is an excellent example of scientific intuition. The biochemical mechanism of CAM, and in particular the occurrence of carbon dioxide fixation in darkness and the pathway of malic acid conversion to carbohydrates were unknown when Pfeffer wrote his Pflanzenphysiologie. 

Effect of water stress and growth retardants. Ann. Bot. 41,493-500 (1977 a) Chaturvedi,S.N., Zabka,G. Studies on dark fixation of carbon dioxide in Kalanchoe. II. Effect of interaction of photoperiodic induction with water stress and growth retardants. Ann. Bot. 41,501-505 (1977b)... 

Kaplan, A., Gale,J. Separation of respiration from dark fixation of carbon dioxide in CAM plants. Isr. J. Bot. 25,59 (1975)... 

Kaplan, A., Gale,J., Poljakoff-Mayber,A. Simultaneous measurement of oxygen, carbon dioxide, and water vapour exchange of intact plants. J. Exp. Bot. 97, 214-219 (1976 a) Kaplan, A., Gale,J., Poljakoff-Mayber,A. Resolution of net dark fixation of carbon dioxide into its respiration and gross fixation components in Bryophyllum daigremontianum. J. Exp. Bot. 97,220-230 (1976 b)... 

Thompson, A., Vogel, J., Lee,R. Carbon dioxide uptake in relation to a plastid inclusion body in the succulent Kalanchoe pinnata Persoon. J. Exp. Bot. 28, 1037-1041 (1977) ThurloWjJ., Bonner,J. Fixation of atmospheric CO2 in the dark by leaves of Bryophyllum. Arch. Biochem. 19, 509-511 (1948)... 

Zabka,G.G., Edelman,J. Pre-illumination as a factor in the dark-fixation of carbon dioxide by leaf disks of Kalanchoe blossfeldiana var. Feuer Bliite. J. Exp. Bot. 13, 11-19 (1961b) Zabka,G.G., Gregory, F.G., Edelman, J. Dark fixation of carbon dioxide in Kalanchoe blossfeldiana in relation to photoperiodism. Nature (London) 813,1375 (1959)... 

Werdan, K., Heldt, H.W., and Milovancer, M., 1973, The role of pH in the regulation of carbon dioxide fixation in the chloropiast stroma. Studies on CO2 fixation in the light and dark, Biochem. Acta, 396 276. 

The isolation of chloroplasts capable of performing all of the reactions normally regarded as photosynthetic including the fixation of carbon dioxide, the evolution of oxygen and the synthesis of sugars and polysaccharides unequivocally demonstrates that the site of photosynthesis is the chloroplast. Experiments involving the fractionation of chloroplasts have further shown that the dark reactions associated with carbon dioxide fixation are located in the stroma of the chloroplast and the light reactions , electron transport and photophosphorylation, takes place in the lamellar systems. 

The best known case of a rhythm in metabolic activity is that of the dark fixation of carbon dioxide in the leaves of Crassulacean... 

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