Vinay Pagay*
*University of Adelaide, PMB 1, Glen Osmond, Australia (vinay.pagay@adelaide.edu.au)

Tensiometers measure the water potential, a measure of the activity of water, of any system. Here, we report for the first time on the use of novel microtensiometers (MTs) to provide high temporal resolution water potential measurements in field-grown grapevines. The MTs were embedded in mature Shiraz and Cabernet Sauvignon grapevines in a South Australian vineyard and validated versus conventional measures of vine water status, including leaf and stem water potentials and leaf stomatal conductance. MT-measured water potentials were consistently higher than both leaf and stem water potentials and reflected the vine’s trunk water potential (Ψtrunk). Diurnal Ψtrunk measurements were observed under varying soil moisture and environmental (vapor pressure deficit; VPD) conditions revealing the daily dynamic nature of plant water status at high temporal resolution. MTs tracked VPD more closely than soil moisture. Under heatwave conditions, Shiraz vines allowed Ψtrunk to drop to values much lower than in Cabernet Sauvignon, reflecting a relative degree of anisohydricity in Shiraz. Our results indicate that MTs could be used reliably for continuous measurements of trunk water potential in woody plants and trees and could be a useful tool for irrigation scheduling in irrigated horticulture.

Funding Support: Wine Australia