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Circadian Rhythm of Leaves of Phaseolus angularis Plants Grown in a Controlled Carbon Dioxide and Humidity Environment ¹

^a Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706

Leaf movements of primary leaves of Phaseolus angularis Wight. were studied in an environment with controlled levels of CO₂, relative humidity, temperature, light, nutrient concentrations, and water tension. Rhythmic circadian movements and irregular short period movements were evident as the leaves unfolded and persisted during development of the leaves. The mean period in rhythmic circadian movement was 27.3 hours with no significant differences in period between plants of the same or different experiments. The leaf movements of separate plants were not closely synchronized.

A system is described for growing plants for extended periods while collecting data with time lapse photography. The system was developed to minimize disturbances to the plants.

The occurrence of leaf movements in plants grown from the time of seeding in an environment free of any recognized fluctuation which could stimulate leaf movements supports the hypothesis that leaf movement rhythms originate spontaneously within the plant.