Les rythmes endogènes des mouvements foliaires chezMimosa pudicaL.

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Abstract
Endogenous Rhythms in Mimosa pudica L. Leaf Movements. The rhythmic movements performed by the leaves of the “Sensitive plant”, Mimosa pudica L., observed by time lapse photography, result of periodical turgor variations taking place in the parenchymatous cells of specialized motor organs. These turgor variations are associated with membrane permeability changes and ionic movements. These leaf movements allow to specify the temporal organization of this plant. Statistical analysis of observed periodicities in leaf movement shows that, in alternating conditions of light and dark (L/D:14/10) three distinct rhythms exist: a circadian rhythm synchronized by the photoperiodic cycle (τ = 24 hrs), and two ultradian rhythms with mean period values 3.8 hrs and 0.5 hrs respectively. In constant conditions from germination (L/L), the leaf behavior is strongly modified, but the three period values are found again (mean period values of 25.1 hrs, 3.5 hrs and 0.6 hrs respectively). The occurence of many rhythms with various periods taking place in the same organ is discussed in reference to observations effected on other biological subjects. Then, it appears that the period value within 2 and 4 hrs may be considered as a characteristic one in plants.