Viability of plant cell suspensions exposed to homogeneous ultrasonic fields of different energy density and wave type

Exposure of Pettunia hybrida cell suspensions to ultrasound at a frequency of 2.43 MHz in a standing wave held at an energy density of 70 J m(-3) (pre ssure amplitude of 0.78 MPa) decreased their mean viability to 35% after 20 min of sonication. A comparison of propagating wave and standing wave trea tments at equal frequency (2.15 MHz) and energy density (8.5 J m(-3)) showe d, in the first case, a rapid decline in mean viability of cells (to 30% af ter 10 min of sonication) and, in the second case, a retaining of the initi al viability (95%), respectively. Cells sonicated 4 days after subculture w ere more sensitive than cells sonicated 2 or 6 days after transfer to new c ulture medium. It was concluded that cellular viability depends primarily o n the acoustic energy density, the exposure time, and the mechanical proper ties of the cells determined by age. As a consequence of the trapping of ce lls in the anti-node planes of the standing wave, propagating wave fields r educed cellular viability compared with standing wave fields at equal energ y density. (C) 2000 Elsevier Science B.V. All rights reserved.