title: Oxaloacetate as the Source of Carbon Dioxide for Photosynthesis in Bundle Sheath Cells of the C(4) Species Panicum maximum.
abstract: 3-Mercaptopicolinic acid (3-MPA), an inhibitor of phosphoenolpyruvate carboxykinase, was employed to study the role of organic acid decarboxylation during C(4) photosynthesis. Treatment of detached Panicum maximum leaves with 5 mm 3-MPA inhibited photosynthesis 70 to 75%. Oxygen was found to have no effect on the degree of inhibition. The postillumination (14)CO(2) burst associated with P. maximum photosynthesis was almost abolished by 5 mm 3-MPA. The turnover rates of malate and aspartate during C(4) photosynthesis were severely reduced as well as the rates of formation of C(3) cycle intermediates in P. maximum leaves treated with 3-MPA. These results are interpreted as direct evidence for the fixation of CO(2), arising from the decarboxylation of oxaloacetate, by the C(3) cycle in bundle sheath cells of P. maximum leaves.
authors: Department of Botany, University of Georgia, Athens, Georgia 30602.
authors: T B
authors: TB
authors: Ray
authors: C C
authors: CC
authors: Black