During washing of excised beetroot tissue discs the most prominent changes in fine structure were the development of amyloplasts and enhancement of the membrane systems of the Golgi bodies and endoplasmic reticulum. When D(-)threo-chloramphenicol was present during washing, the appearance of crystalloid bodies in the cytoplasm was accelerated. Staining with phosphotungstic acid-chromic acid (PTAC) was largely restricted to the plasma membrane in freshly excised cells. After washing, additional PTAC staining was associated with the starch grains and with whorled arrangements of the plasma membrane close to the developing amyloplasts. Silver nitrate staining showed an intense particulate reaction in the vacuole and in the region of the tonoplast; the vacuolar staining was reduced in washed tissues. Biochemical analysis showed increased activities for both glucose-6-phosphatase and peroxidase. Cytochemical staining for glucose-6-phosphatase was localized largely in the plasma membrane and tonoplast in both fresh and washed tissues. Peroxidase staining was most prominent in the cell wall in freshly excised tissues. After washing, the reaction of the cell wall was increased and additional staining appeared associated with the Golgi bodies and endoplasmic reticulum. These findings are discussed in relation to the development of the wound response in plant tissues.