ONTOGENY AND CYTOCHEMISTRY OF ALKALOIDAL VESICLES IN LATICIFERS OF PAPAVER SOMNIFERUM L. (PAPAVERACEAE)

Development of alkaloidal vesicles in laticifers of opium poppy, Papaver somniferum L., was investigated at the ultrastructural level. Laticifer initials possessed abundant endoplasmic reticulum throughout their dense cytoplasm. During differentiation the endoplasmic reticulum organized into long, folded sheets that were parallel to the longitudinal walls along the periphery of the cell. Vesicles appeared to be derived from dilation of endoplasmic reticulum. This relationship was confirmed through cytochemical data obtained with zinc iodide-osmium tetroxide and osmium tetroxide impregnation. Alkaloidal vesicles had electron-dense regions or caps that occurred early in laticifer differentiation, but these caps became less conspicuous in mature cells. Caps appeared to be derived from small particles which condensed along the inner surface of the vesicle membrane and subsequently accumulated at one or two positions along the membrane of the vesicle.