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A circadian leaf movement has been found in Phaseolus vulgaris var. Pinto that will persist under constant temperature and continuous fluorescent light. The period of leaf movement was approximately 26 hours in length, and the amplitude did not diminish for at least 4 weeks. Leaf movements were similar for plants grown in either 1100, 4950, 7700, or 10,450 lumens per square meter. This is the first clearly defined persistent circadian rhythm reported for leaves of higher plants.

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The rhythmic leaf movement of Biloxi soybean (Glycine max) and its relationship to the rhythmic flowering response were studied. The movements of fully expanded trifoliate leaves were recorded with kymographs and time lapse photography in growth chambers. A comparison between the leaf movement rhythm and the rhythmic flowering response indicates that a high degree of similarity exists between the two rhythms. A definite relationship was shown to exist between the direction of the leaf movement and the photophil-photophobe phases of the rhythmic flowering response.Short light perturbations may affect flowering by interacting directly with the flowering process while not affecting the basic endogenous rhythm. Long light perturbations may affect flowering by phase shifting the basic endogenous rhythm. Thus, light perturbations appear to have a dual effect on the flowering response of Biloxi soybean. The hypothesis that both the flowering rhythm and the leaf movement rhythm are coupled to the same basic oscillator is supported by the similarity of the phase shifts induced in the two rhythms by identical light perturbations.