Can you hear plants call for help? Lidewei Vergeynst, a PhD student at UGent has found a way to listen to plants and pinpoint when they are acutely drought-stressed, rather like a heart monitor for plants.
Plants suck water up from their roots through tubes (veins) and then transpire that water out through their leaves. This means that the column of water in the tube is always in negative pressure. As the soil gets drier, the plant needs to exert more pull to extract the water and if the soil is very dry, small air bubbles form in the water columns. Using an acoustic detector (like a stethoscope) on the stem or branch of a plant, it’s possible to hear those air pockets, called cavitation, as faint ‘clicks’.
Scientists count the clicks to determine the level of water-stress the plant is suffering. However past methods found that other factors could also cause clicking sounds, so Vergeynst’s work is important as she has discovered a way to analyse and differentiate between the various clicking sounds to focus on those associated with acute drought stress.
This new tool can be used with other sensors that measure how much water a plant is using to quantify a plant’s water needs more accurately and also pinpoint the moment beyond which wilting cannot be reversed. As this ‘hydraulic failure’ is part of forest dieback, the research could help save both trees and crops, especially as areas become drier and warmer from climate change.