Kaan Kurtural,* Runze Yu, and Daniele Zaccaria
*University of California Davis, 1 Shields Avenue, Davis, CA, 95616 (skkurtural@ucdavis.edu)

Seasonal management of plant water deficits and the accompanying physiological responses is a critical aspect of viticultural production. Presently, water deficits are examined via in-season measurements of stem water potential or post-season analy­sis of must carbon isotope ratios, with the former limited by reliance on arduous mea­surements and the latter providing information post-season. Therefore, leaving a gap in reliable, real-time measurements of plant water deficits. Technological advances in the field of surface renewal have provided a cheap and reliable method to quantify the actual evapotranspiration of an agricultural production. This work used surface renewal calculations to derive a novel index of grapevine water stress, the b-index, and relates b to measurements of stem water potential, leaf-gas exchange, and must carbon isotopes from three experimental vineyards over the 2020 and 2021 growing seasons. We offer the b-index as a reliable indicator of real-time vineyard water status and as a proxy for physiological responses in water-stressed vineyards. The coupling of atmospheric controls on evapotranspiration with plant physiological responses makes b a powerful tool for irrigation management.

Funding Support: UC ANR