The capacity of intact cells of roots excised from summer squash plants (Cucurbita pepo L. cv Early Prolific Straightneck) to synthesize purine nucleotides de novo was investigated. Evidence that purine nucleotides are synthesized de novo included: (a) demonstration of the incorporation of [1-(14)C]glycine, [2-(14)C]glycine, NaH(14)CO(3), and H(14)COONa into total adenine nucleotides; (b) obser...