Automatic Device for Controlling Lengths of Light and Dark Periods in Cycles of any Desired Duration

Abstract

A simple apparatus for shifting plants automatically from light to darkness or vice versa is described. The apparatus (photocycler) consists of 4-drawer, 52 inches high, 18 inches wide and 26.5 inches deep filing cabinets. The upper 2 drawers and bottom drawer of a cabinet are discarded while the 3d drawer is used to shift the plants in and out of the cabinet body. With suitable modification, the cabinet when closed, serves as a dark room for plants inside the drawer while outside the plant receives bright fluorescent light. An automatic watering system is provided so that plants are watered twice a day whether they are in light or darkness. A reversible electric motor with a pinion and rack arrangement is housed in the cabinet to open or close the drawer. The plants can be moved in or out of the cabinet at any predetermined time by suitable electric clock which controls the motor. For experiments with varying time regime a device using a roll of paper tape is described. Through a series of punched holes in the paper tape of a recording potentiometer electric impulses are used to move the drawer in or out at any desirable time. Such a system can control 18 photocycles in the experiment.