Wilting Coefficient

The percentage of water content of a soil where a plant will not recover from the lack of available water unless additional water is added to the soil to aid recovery: At this stage a plant will be at wilting point because the soil cannot supply any water, which is held at about -15 bar, to the plant. If additional water is not supplied to the soil, or if the plant cannot become effectively dormant for a period until adequate water is available, then permanent wilting point will be reached and no matter how much additional water is then added to the soil, the plants imminent death is certain.
(Source: Lyman J. Briggs & H.L. Shantz, ‘The wilting coefficient and its indirect determination’, https://www.journals.uchicago.edu/doi/pdf/10.1086/330708, accessed 18th March 2023)