Immunocytochemical andCytochemical Localization of

Cytochemical andimmunocytochemical methods wereused tolocalize photosystems IandIIinbarley (Hordeum vulgare L.cvHimalaya) chloroplasts. PSIactivity, monitored bydiaminobenzidine oxidation, was associated with thelumen side ofthethylakoids ofbothgrana andstroma lamellae. TheP700 chlorophyll aprotein, thereaction center ofPSI, was localized onthinsections ofbarley chloroplasts using monospecific antibodies tothis protein andtheperoxidase-antiperoxidase procedure. Results obtained byimmunocytochemistry weresimilar tothose ofthe diaminobenzidine oxidation: bothgrana andstromalamellae contained immunocytochemically reactive material. Boththegranaandstroma lamellae werealsolabeled whenisolated thylakoids werereacted with theP700 chlorophyll a protein antiserum andthenprocessed bythe peroxidase-antiperoxidase procedure. PSIIactivity waslocalized cytochemically bymonitoring thephotoreduction ofthiocarbamyl nitroblue tetrazolium, areaction sensitive tothePSIIinhibitor, DCMU.PSII reactions occurred primarily onthegrana lamellae, with weaker reactions onthestroma lamellae.