THE ISOLATION AND CHARACTERIZATION OF MUTANTS OF THE C-4 PHOTOSYNTHETIC PATHWAY

Three novel classes of the C-4 plant Amaranthus edulis are described. (1) A mutant that contains less than 10% of the normal activity and pr otein of phosphoenolpyruvate carboxylase. (2) A mutant that is deficie nt in NAD-malic enzyme activity, but contains the normal two subunits of the enzyme protein. (3) Four mutant plants that accumulate high con centrations of glycine following exposure to air. A common characteris tic of all the mutant plants is that they grow poorly in air and exhib it very low rates of photosynthetic CO2 assimilation. The characterist ics of the mutant lines are discussed with reference to our current kn owledge of the regulation of the C-4 photosynthesis pathway. The possi bility that C-4 plants undergo photorespiratory nitrogen and carbon me tabolism when grown in air is considered in detail.