Scientists have found acoustic signs, created by severely drought-tolerant plants.
The fact that the tree makes a sound (in addition to the rustling of leaves in the wind) is not something new. However, the sound emitted may indicate that the physical condition is quite new to researchers.
Scientists from Grenoble University, France, have demonstrated that, when drought occurs, plants produce distinctive sounds; And they also figured out how the tree made these sounds.
To understand this problem, it is necessary to understand the process of transporting water in plants: plants take water from the ground and transfer them through special ducts called Xylem thanks to the repulsion between molecules, creating a water column in each xylem tube. However, when dried up, the plant is forced to create a stronger attraction to absorb water. If the pressure is greater than the force created between molecules, the water column will break and form air bubbles. This process is called effervescence. The more bubbles, the faster the tree dies.
When "thirsty", the tree makes special sounds to call for help.
To confirm that these air bubbles are the culprits that make noise in the drought, the scientists described this process in the laboratory.
They put a piece of pine wood, together with its xylems, into a pot of gel. Later, the researchers let the water in the gel evaporate. They recorded the whole process and also the sounds caused by the bubbling phenomenon in Xylem. They found that half of the sound produced by the tree was due to foaming and that the sound had special acoustic signs.
From this finding, scientists believe that forest managers can use a special portable acoustic device to detect drought.