Phosphorylase in the Maize Endosperm

Abstract

Phosphorylase in the developing maize endosperm is identified histochemically, using the glucose- 1-phasphate method of Yin and Sun. Phosphorylase occurs in endosperms older than 5 days after pollination and is located in plastids, in the knobs of mitochondria-like filaments, and in transition stages between the filaments and plastids. Because phosphorylase is found in plastids prior to normal starch synthesis, and because it is shown to occur in cytoplasmic inclusions and cells which normally do not form starch, it is concluded that the mere presence of phosphorylase is not a limiting factor for determining the time or place of normal starch synthesis in the maize endosperm.