Indexed on: 26 Jun '08Published on: 26 Jun '08Published in: Biologia Plantarum
A previous report on the mechanism of diurnal oscillations is supplemented here by data concerning causes of irregularities in their oscillation trajectories. Cinematographic records showed that the final trajectory is significantly influenced by the circumnutation oscillations of the stem. Amplitudes of these oscillations which are small(ca 0.7 mm as compared with 5 X larger amplitudes of leaves when measured at the leaf tip) can be enlarged up to 10 times the value at the apical tip of the leaf. These nutations are responsible for side-deviations of space spirals of growing leaves in the direction of their shorter half axis. This explanation is based on the occurrence of side-deviations of leaf trajectories which correlate with the actual position of the nutation phase of the stem. Concurrent frequencies of the two oscillations (= diurnal rhythm) indicate that nyctinastic oscillations of the leaves are controlled by the same mechanism as is the circumnutation of the stem.