Photosynthesis Hatch-Slack pathway

C4 plants Plants that employ the Hatch-Slack pathway during photosynthesis. C4 plants are named such because they employ an intermediate compound, oxaloacetic acid that contains four carbon atoms. These plants moderately discriminate (8 to 14% ) against C during carbon incorporation. C4 plants are usually higher land plants that are specially adapted to dry and low-/JCO2 conditions. 

Most plants reduce CO2 to carbohydrate according to the well-known Calvin-Benson or C3 pathway, where the initial product of photosynthesis is the 3C compound phosphoglycerate. Fixation of CO 2 to phosphoglycerate occurs with the assistance of the enzyme ribulose bisphosphate (RuBP) carboxylase, which discriminates heavily against C02 (11). Consequently, plants with C3 photosynthesis have 6 values that average -27.0 (12). Plants with the Hatch-Slack or Ci,... 

Some plants employ a photosynthetic pathway creating at first a three-carbon phosphoglyceric acid (C3 or Calvin-Benson photosynthesis). These plants fractionate isotopes more intensely, and so have more negative values (-33%o to —22%o PDB) than plants which use a photosynthetic pathway creating at first a four-carbon malic and aspartic acid (C4 or Hatch-Slack photosynthesis -16%o to -9%o PDB). Crassulacean acid metabolism (CAM) is yet another photosynthetic pathway, which creates organic matter of intermediate isotopic composition (-35%o to -ll%o PDB). Methanogenic microbes are even more extreme in their fractionation of the light isotope (5 C down to -110%o and typically -60%o PDB ... 

The interpretation of CAM in this sense was stimulated by the discovery of another variant of photosynthesis, the C4-pathway (see Black, 1973 Hatch and Slack, 1970 Hatch, 1976). Because this newly discovered photosynthetic pathway is recognized to be very closely related to the CAM pathway, the work on the latter became intensified during these last years. The increased effort in research on CAM provided a large amount of new data which can now be collected and critically evaluated. We have undertaken this as one of the goals of the present monograph. 

Hatch, M. D. 8 Slack, C. R. (1966). Photosynthesis by sugarcane leaves. A new carboxylation reaction and the pathway of sugar formation. Biochemical Journal 101, 103-111. 

Hatch,M.D., Osmond,C.B. Compartmentation and transport in C4 photosynthesis. In Transport in plants III. Enzyclopedia of plant physiology. New series, Vol. 3. Stocking, C.R., Heber,U. (eds.), pp. 144-184. Berlin, Heidelberg, New York Springer 1976 Hatch, M.D., Slack, C.R. Studies on the mechanism of activation and inactivation of pyruvate, phosphate dikinase. A possible regulatory role for the enzyme in the C4 dicarboxylic acid pathway of photosynthesis. Biochem. J. 112,549-558 (1969)... 

Slack, C.R., Hatch, M.D., Goodchild,D.J. Distribution of enzymes in mesophyll and parenchyma-sheath chloroplasts of maize leaves in relation to the C -dicarboxylic acid pathway of photosynthesis. Biochem. 3.114,489-498 (1969)... 

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