Hyperspectral signals in the soil: Plant–soil hydraulic connection and disequilibrium as mechanisms of drought tolerance and rapid recovery

• Published in: Plant, cell and environment Vol. 47; no. 11; pp. 4171 - 4187
• Main Authors: Song, Yangyang, Sapes, Gerard, Chang, Spencer, Chowdhry, Ritesh, Mejia, Tomas, Hampton, Anna, Kucharski, Shelby, Sazzad, T. M. Shahiar, Zhang, Yuxuan, Tillman, Barry L., Resende, Márcio F. R., Koppal, Sanjeev, Wilson, Chris, Gerber, Stefan, Zare, Alina, Hammond, William M.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.11.2024
• Subjects: Corn; drought; Drought resistance; Extreme drought; Extreme values; Hydraulics; hyperspectral reflectance; Moisture content; Peanuts; Plant layout; Plants (botany); Predictions; pre‐dawn disequilibrium; Recovery; Reflectance; Rhizosphere; Soil water; Spectral reflectance; Sweetcorn; Water potential; pre‐dawn disequilibrium; recovery; hyperspectral reflectance; drought; rhizosphere
• ISSN: 0140-7791; 1365-3040; 1365-3040
• DOI: 10.1111/pce.15011

Predicting soil water status remotely is appealing due to its low cost and large‐scale application. During drought, plants can disconnect from the soil, causing disequilibrium between soil and plant water potentials at pre‐dawn. The impact of this disequilibrium on plant drought response and recovery is not well understood, potentially complicating soil water status predictions from plant spectral reflectance. This study aimed to quantify drought‐induced disequilibrium, evaluate plant responses and recovery, and determine the potential for predicting soil water status from plant spectral reflectance. Two species were tested: sweet corn (Zea mays), which disconnected from the soil during intense drought, and peanut (Arachis hypogaea), which did not. Sweet corn's hydraulic disconnection led to an extended ‘hydrated’ phase, but its recovery was slower than peanut's, which remained connected to the soil even at lower water potentials (−5 MPa). Leaf hyperspectral reflectance successfully predicted the soil water status of peanut consistently, but only until disequilibrium occurred in sweet corn. Our results reveal different hydraulic strategies for plants coping with extreme drought and provide the first example of using spectral reflectance to quantify rhizosphere water status, emphasizing the need for species‐specific considerations in soil water status predictions from canopy reflectance. Summary Statement We developed models to accurately predict rhizosphere water status from hyperspectral imaging of roots and soil. We found canopies cannot always accurately predict rhizosphere water status—as our experiment revealed soil–plant disequilibrium in one species (sweet corn) but not another (peanut).