"Listen to the Trees!" A tribute to the father of modern cavitation research, Professor John Milburn, on the 20th anniversary of his untimely death

Abstract

Over the last 35 years, the study of cavitation in plants has become an accepted and important component of the water stress studies performed by plant physiologists. Although the existence of cavitation had been known since Berthelot’s (1850) pioneering work on the tensile strength of water in glass tubes, the tensions at which it occurred in such systems were far more negative than were considered likely to occur in plants. It is to the late Professor John Milburn’s sharp observational powers, lateral thinking and problem-solving approach — illustrated by his pioneering detection of cavitation in plants — that we owe today’s field of cavitation research. John Milburn was constantly thinking of new ways to approach and solve plant physiological problems. In 1966, Milburn and Johnson published their seminal work on the occurrence of cavitation in plants, using data collected via a record player needle and an amplifier. After the invention of the Scholander pressure chamber (Scholander et al. 1965), it became possible to measure easily the xylem pressures at which plants cavitated. Milburn and McLaughlin (1974) found that such pressures were within the physiological ranges that plants experienced and so the phenomenon of cavitation in plants under stress became a fruitful field of research. Professor John Milburn was tragically killed in a flying accident in 1997. The premature loss of such a great scientist, aged only 60, was felt keenly in the Botany Department of the University of New England, Armidale, Australia, where he had been a Professor for 16 years, and also around the world. This article is a tribute to Professor John Milburn, encompassing several of his key discoveries (a rare recording of the sound of cavitation occurring in the audible range is included in this tribute), as well as some of the many aspects of the man. It is timely, on the 20th anniversary of his death, to remind ourselves that today’s experimental water stress research would be the poorer without John Milburn’s pioneering work.