Modified Photoelectric Device for Recording Leaf Movements

The description of a photoelectric device for monitoring leaf movements was published previously (5). This instrument eliminated physical attachment of sensors to the plant and provided a direct readout of up and down movements of leaves during light periods. The equipment has been modified to monitor rotational movements of the leaf about its longitudinal axis while simultaneously monitoring up and down movements. In addition, the servo-actuating incandescent radiation source has been replaced with a modulated infrared source to assure that radiation originating from the leaf monitor does not influence leaf movements and to permit the recording of leaf movements during periods of darkness, as well as during periods of light. Samples of recordings obtained with it are described.