Imaging of photosynthetic and respiratory activities of a single algal protoplast by scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) based on the reduction current f or oxygen was used for imaging of respiratory and photosynthetic activities of single, living protoplasts. In the dark, the image of the protoplast ap peared as a spot with lower oxygen concentration due to consumption of oxyg en by respiration. Under light irradiation, the protoplast appeared as the opposite image because it generated oxygen by photosynthesis. SECM images c learly displayed a decrease in photosynthetic activity of the protoplast in jected with 3-(3,4-dichlorophenyl)- 1, 1-dimethylurea (DCMU), a photosynthe tic inhibitor.