Monitoring cotton water status with microtensiometers

Abstract Stem water potential (Ψ stem ) is a key indicator for assessing plant water status, which is crucial in understanding plant health and productivity. However, existing measurement methods for Ψ stem , characterized by destructiveness and intermittency, limit its applicability. Microtensiometers, an emerging plant-based sensor, offer continuous monitoring capabilities and have shown success in certain vine and tree species. In this study, we investigate the efficacy of microtensiometers ability to monitor the Ψ stem of cotton ( Gossypium hirsutum L.) under three distinct irrigation treatments in Maricopa, Arizona, an extremely hot, arid environment. We analyze the diurnal dynamics of Ψ stem across the irrigation regimes and compare these measurements with midday leaf water potentials (Ψ leaf ) obtained using a dewpoint potentiometer. Our results demonstrate that the microtensiometer-derived Ψ stem closely follows known diurnal patterns of Ψ leaf , tracking with vapor pressure deficit (VPD) and responding to variations in irrigation levels and soil moisture content. Time cross-correlation analysis reveals an 80-minute lag in Ψ stem response to changing VPD under non-water limiting conditions, which shortens under water-limiting conditions. Additionally, we establish a robust linear relationship ( R 2 adj = 0.82) between Ψ stem and Ψ leaf , with this relationship strengthening as water availability decreases. Notably, we observe mean gradients of 1.2 and 0.06 MPa between soil vs. stem and stem vs. leaf water potentials, respectively. Moreover, Ψ stem data proves to be more sensitive in distinguishing between irrigation treatments earlier in the growing season compared to Ψ leaf , leaf temperature and leaf gas exchange parameters. These findings highlight the utility of microtensiometers as valuable tools for monitoring water status in smaller-stemmed row crops such as cotton.