Plant water stress: how much does drought in the soil and in the atmosphere matter?
In the face of changing climates and rising temperatures, understanding how plants manage water is more important than ever. A recent study sheds light on this by introducing a groundbreaking metric to measure how plants regulate their water status on a daily scale.
Traditionally, scientists have focused on seasonal changes to study plant water stress, primarily linking it to soil drought. However, plants are also influenced by changes in air conditions that occur daily. Specifically, the vapor pressure deficit (VPD)—a measure of the drying power of the air, is minimal at night and maximal during warm afternoons. With global temperatures on the rise, VPD is already playing a bigger role than in the past in shaping plant health and behaviour and its importance will continue to grow.
The new metric, called the stringency of water potential regulation, fills a crucial gap. It quantifies the individual and combined effects of soil and atmospheric drought on plant water status and can be applied daily. Unlike older methods that focus only on soil water availability, this metric reveals how plants respond to rapid changes in air temperature and VPD, helping researchers better predict how plants might cope with warming climates.
Using data from experiments that manipulated air temperature and VPD, researchers tested this metric and found that VPD had a significant impact on plant water status, as large or even larger than soil drought. This result, published in a FORGENIUS-funded paper, highlights the strong influence of atmospheric conditions on plants, alongside soil drought.
This metric opens the door to exciting applications, from understanding plant responses at the individual level to assessing ecosystem health via remote sensing. As climate challenges grow, tools like these could prove vital for sustainable forest management and agricultural resilience.