Observations on the combined effect of ultrasound and x-rays on the growth of the roots of Zea mays.

The roots of Zea mays seedlings were exposed to ultrasonic radiations (1 MHz) of intensities in the range of 0-1-0-8 W cm-2 (pulsed or continuous modes) for times between 2 and 60 min, together with an X-ray dose of 775 rad which was given before, after or simultaneously with the ultrasound. These experiments have shown that ultrasound and X-rays seem to act independently of each other, suggesting that the mechanism of damage due to X-rays is different from that due to ultrasound. An increase in the X-ray effectiveness under the action of ultrasound, as reported by various authors who worked with different tissues, has not been found.