Scientists have recorded the ultrasound emitted by plants in danger.

The researchers recorded the sounds made by tomatoes and tobacco grown in greenhouses. Healthy plants made clicks and pops that became much more frequent when the plants were deprived of water or stems were cut. Sounds are audible up to five meters away, but they are in the range of 40 to 80 kHz, which a person cannot hear. However, insects and small mammals can perceive such frequencies. Most likely, the sounds occur when the vessels of plants are destroyed, forming air bubbles. It is unlikely that these sounds are an attempt at communication, but other animals can receive information when they hear them.