The occurrence and ultrastructure of chloroplasts in the phloem parenchyma of leaves of C4 dicotyledons.

Chloroplasts were found to be common within the phloem parenchyma of leaves of dicotyledons, although they were not observable, at the light microscope level, in the vascular cells of any grasses examined. The phloem-cell chloroplasts of Boerhaavia paniculata L. and Portulaca oleracea L. (both C4 plants) were structurally similar to each other, even though the chloroplasts of their surrounding bundle sheaths were of different types. They were also similar to the phloem-cell chloroplasts of Phaseolus vulgaris L. (C3 plant). Although consistently small, all vascular plastids appeared normal. The extent of their functionality is unknown.