Biophoton measurement of herbivore-induced plant responses

Abstract

We studied spontaneous photon emission from kidney bean leaves infested with kanzawa spider mites, Tetranychus kanzawai Kishida (Acari: Tetranychidae). Strong photon radiation was observed from veins strongly infested with spider mites. Temporal changes in the total photon intensity can be described by two different logistic curves: the one was thought to be due to injury caused by the mites and the other due to induced responses. Photon intensity of the wavelength ranging from 500 to 700 nm increased monotonously soon after spider mites attacked. Photon intensity from 300 to 400 nm began to increase about 20 h after infestation and showed two peaks at about 72 and 120 h. The former phenomena may be the result of direct injury (physical stresses) and the latter to physiological (biochemical) actions related to defensive responses. These results suggest that photon measurement is a powerful tool for evaluating plant responses to herbivory.