Quantifying Rhythmic Movements of Albizzia julibrissin Pinnules.

The cosinor technique, previously applied to studies of animal rhythms, is used to assess the circadian rhythm in pinnule movement of Albizzia julibrissin. The method provides a quantitative approach for studying rhythm properties of either intact or excised pinnules. Phase shifting in A. julibrissin, as compared to the usually slower phase shifts of various circadian phenomena in the insect, bird, and mammal, occurs within 1 day or two. Rhythm adjustment in the pinnules takes place more rapidly when the lighting regiment is advanced than when it is delayed.