Acoustic Radiation Torque Research Articles

Perturbation of plant-cell contents by ultrasonic micro-irradiation

An account is given of mechanically induced disturbances in a vacuolate plant cell when part of its wall is set into low-amplitude vibration at ultrasonic frequencies. Beginning at vibration amplitudes ξ0 in the vicinity of 0.1 μm distortions of the vacuolar membrane occur. These take the form of evaginations into the vacuole; it is proposed that they result from flow of fluid along the parietal channel. The rate of growth of evaginations is in order-of-magnitude agreement with simplified theory, in which it is assumed that the flow arises from gradients of radiation pressure. Continued sonation at an amplitude of about 0.2 μm leads to rupture of the vacuolar membrane and fragmentation of the cytoplasm; plastid-containing fragments are then released into the vacuole. Motions in the vacuole include acoustic microstreaming as well as particle migrations believed to result from radiation pressure. Spinning motions are also seen, and are ascribed to acoustic radiation torque. Considerable variation is seen in post-irradiation response. While some cells die after sonication in which no viable changes were seen, others show a surprising ability to recover from apparently severe destruction.