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Plant Physiology 82:1081-1089 (1986) © 1986 American Society of Plant Biologists Mannose Metabolism in Corn and Its Impact on Leaf Metabolites, Photosynthetic Gas Exchange, and Chlorophyll Fluorescence 1Department of Biological Sciences, Wellesley College, Wellesley, Massachusetts 02181, Department of Chemistry, Wellesley College, Wellesley, Massachusetts 02181, Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
When intact corn leaves were provided millimolar concentrations of D-mannose through the transpiration stream photosynthesis was inhibited; 5.7 millimolar resulted in a 50% inhibition of the carbon exchange rate. This inhibition was partially reversible by the addition of orthophosphate to the feeding solution. Mannose metabolism by corn leaves was limited in that it did not act as a resource for sucrose or starch synthesis. Mannose 6-phosphate accumulated in the leaf tissues and was slowly metabolized by a pathway involving mannose 1-phosphate. Correlated with the mannose-6-phosphate accumulation were decreases in ATP, orthophosphate, sucrose, and phosphoenolpyruvate and increases in starch and maltose. When provided in the transpiration stream mannose had access to both mesophyll and bundle sheath cells. Mannose feeding led to oscillations in steady state chlorophyll fluorescence emission (680 nanometers) and an elimination of the Kautsky effect during fluorescence induction. Pyridoxal 5-phosphate and 2,4-dinitrophenol were found to be inhibitors of CO2 exchange when provided in the transpiration stream of intact corn leaves. However, Pyridoxal 5-phosphate induced a quenching of steady state fluorescence while 2,4-dinitrophenol led to an increase in fluorescence emission.
1 Support was provided by a Brachman Hoffman Fellowship and a National Science Foundation grant DMB8410 to G. C. H. The High Field NMR Facility at the Francis Bitter National Magnet Laboratory is supported by grant RR 00995 from the Division of Research Resources of the National Institutes of Health and by National Science Foundation Contract C-670. This article has been cited by other articles:
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