Subcellular localization of the red-absorbing form of phytochrome by immunocytochemistry

An immunocytochemical technique was used to localize the red-absorbing form of phytochrome at the light- or electron-microscope level in etiolated barley (Hordeum vulgare L.) coleoptile tip, rice (Oryza sativa L.) coleoptilar node, maize (Zea mays L.) coleoptile tip, rye (Secale cereale L.) coleoptile tip and coleoptilar node, and oat (Avena sativa L.) root cap. Staining for phytochrome in the cells was found to be generally distributed throughout the cytoplasm. In addition, barley also showed staining around the periphery of vesicles, and rice showed staining in numerous discrete regions in the cytoplasm. Electron-microscopic localization studies of the nodal region of rye and the root cap of oat indicate staining associated with the nuclear membrane and with the interior of mitochondria and amyloplasts as well as general staining like that observed with the light microscope. Cells of the coleoptile tip of maize were unusual in having heavy staining associated with amyloplasts only.