A hand-held, battery operated, single photon sensitivity phytoluminometer is claimed for rapid, simple nondestructive, noninvasive evaluation of photosynthetic topography in green leaves. All the steps for generating phytoluminescence are performed within a single, light tight enclosure. The sensitivity of the instrument is such that stress induced changes in photosynthesis can be detected seconds after occurrence. Thus phytoluminography is made an easily applied technique for practical use by all those concerned with plant life.