Talk is cheap: rediscovering sounds made by plants
Recent reports of airborne sound emissions by plants under drought stress have generated interest, leading to speculative ideas on plant–animal and plant–plant communication.
Research on sound production by plants is more than 100 years old, with John Milburn demonstrating in 1966 that these sounds are mainly produced by xylem cavitation events and can be detected with dedicated instruments.
Research from 1970 onward has shown that sounds can also be produced by other passive physical processes in plants, and also demonstrated that acoustic emissions can be used to monitor the water status of plants in the field.
The hypothesis that sounds produced by plants are informative for insects feeding on stressed plants, or even for neighboring plants, is attractive but still purely speculative to date.