It is useless to measure the oxygen production every hour for 24 hours because oxygen is produced during day time due to the presence of photosynthesis process. Oxygen is produced in large amount during photosynthesis, some oxygen is used in respiration while the remaining diffuse out from plant body through stomata. After vanishing sunlight, the photosynthesis process stop and no production of oxygen occur. So only measure oxygen production at daytime as compared to every hour for 24 hours.
