Regulation of C/N Interactions in Higher Plants by Protein Phosphorylation

  • Steven C. Huber
  • Werner M. Kaiser
Part of the Plant Gene Research book series (GENE)


In the light, leaves are the primary site of photosynthetic CO2 fixation for synthesis of carbohydrates and also for the reduction of nitrate to ammonium for biosynthesis of amino acids. In many species, sucrose is the major soluble carbohydrate synthesized and also serves as the primary transport form of reduced carbon. Many of the amino acids, synthesized in mesophyll cells are also exported from the leaf, along with sucrose, via the phloem (Riens et al., 1991). Based on measurements of the concentrations of metabolites in the phloem sap versus the mesophyll cytoplasm, Riens et al. (1991) concluded that amino-acid uptake into the phloem is passive in nature and therefore translocation occurs in response to active sucrose uptake and movement from the leaf. Both carbohydrates and amino acids are also stored in the leaf during the photoperiod such that export of reduced-C and -N can continue throughout the night period. In spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.), the rate of export from leaves at night was found to be about 40% of the rate during the light period (Riens et al., 1994).


Nitrate Reductase Crassulacean Acid Metabolism Phosphoenolpyruvate Carboxylase Nitrate Assimilation Sucrose Synthesis 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Springer-Verlag/Wien 1996

Authors and Affiliations

  • Steven C. Huber
  • Werner M. Kaiser

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