THE STRUCTURE OF GRANA IN FLOWERING PLANTS

A model of granum structure, consisting of multiple helical frets wound around each cylindrical granum, is proposed as a representation of granum structure for flowering plants in general. This model was originally formulated for grana in the mesophyll plastids of Zea mays and was subsequently extended to grana of Phaseolus vulgaris by additional studies. The model is now shown to be applicable also to grana in the plastids of Cannabis sativa, Elodea canadensis, Nicotiana rustica, Pisum sativum, and Spinacia oleracea. This sample of seven angiosperms includes genera commonly studied by other workers in their ultrastructural investigations of plastid structure.