The photoconductivity of chloroplasts and the far red light effect.

The photoconductivity of chloroplast films in the dry and the wet state has been investigated. These films were found to behave like typical semiconductors, in agreement with the results of Arnold and co-workers, who have used only dry films. It was found that a steady photocurrent produced in a chloroplast film by blue or red light, can be either stimulated or quenched-depending on the intensity of the illumination-by simultaneous application of far red or near infrared light. This reminds one of the quenching of the photoconductivity of phosphors by infrared light. The interaction of long wave light with light of shorter wavelength in the production of photoconductivity is of interest in relation to the "second Emerson effect," which suggests a similar interaction in photosynthesis.