Histochemical tests onPinus radiatashoot apices throughout the growing season showed marked changes in cell constituents. Reserve proteins and lipids were high in dormant embryos. Following imbibition, starch occurred throughout the apex and tannins were evident after the cotyledons emerged from the seed coat. Intensity of stains for DNA, RNA, and nucleohistones increased first at the flanks of the apex. At 84 days DNA, RNA, and histones displayed a zonate distribution pattern. Total proteins and carbohydrates were distributed fairly uniformly.The distribution of enzyme activity also varied. Initially acid phosphatase (AP) and succinic dehydrogenase (SDH) activities were high throughout the apex. A decrease of AP and SDH activity in the apex preceded epicotyl elongation. At 84 days AP activity differed in various regions of the apex; SDH was fairly uniform throughout the central, apical, and peripheral zones. Staining for peroxidase was evident first around aleurone grains and along cell walls after imbibition. With the onset of needle formation, staining was concentrated in subsurface cells. At 84 days peroxidase activity was concentrated in subsurface cells of the peripheral zone and in the rib meristem.The results of this study indicate that the full apex is metabolically active during vegetative growth and all regions are probably involved in the determination of vegetative form.