WATER RELATIONS AND ULTRASONIC ACOUSTIC EMISSIONS IN CHESTNUT SEEDLINGS

Ultrasonic acoustic emissions (AE) from the stems of Castanea sativa seedlings were recorded in the field during cycles of water stress, relating AE rates to transpiration rates and xylem water potentials. Low AE rates, with a maximum of seven counts per minute, were recorded in water-stressed plants, which experienced water potentials down to -2.5 MPa. After two cycles of drought, each lasting seven days, the rewatered plants displayed lower transpiration rates in comparison to plants irrigated daily. In a laboratory experiment, AE rates as high as 1800 counts per minute were recorded from debarked stem segments.