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bioRxiv · 10.1101/2021.06.23.449675

Dynamic aspects of plant water potential revealed by a microtensiometer

Pagay, V. V.
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Abstract

Water potential is a fundamental thermodynamic parameter that describes the activity of water. In this paper, we describe the continuous measurement of plant water potential, a reliable indicator of its water status, using a novel in situ sensor known as a microtensiometer in mature grapevines under field conditions. The microtensiometer operates on the principle of equilibration of water potentials of internal liquid water with an external vapour or liquid phase. We characterised the seasonal and diurnal dynamics of trunk water potentials ({Psi}trunk) obtained from microtensiometers installed in two grapevine cultivars, Shiraz and Cabernet Sauvignon, and compared these values to pressure chamber-derived stem ({Psi}stem) and leaf ({Psi}leaf) water potentials as well as leaf stomatal conductance. Diurnal patterns of {Psi}trunk matched those of {Psi}stem and {Psi}leaf under low vapour pressure deficit (VPD) conditions, but diverged under high VPD conditions. The highest diurnal values of {Psi}trunk were observed shortly after dawn, while the lowest values were typically observed in the late afternoon. Differential responses of {Psi}trunk to VPD were observed between cultivars, with Shiraz more sensitive than Cabernet to increasing VPD over long time scales, and both cultivars had a stronger VPD response than soil moisture response. On a diurnal basis, however, time cross correlation analysis revealed that Shiraz {Psi}trunk lagged Cabernet {Psi}trunk in response to changing VPD. Microtensiometers were shown to operate reliably under field conditions over several months. To be useful for irrigation scheduling of woody crops, new thresholds of {Psi}trunk need to be developed.

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Pagay, V. V.. 2021-06-24. Dynamic aspects of plant water potential revealed by a microtensiometer. https://doi.org/10.1101/2021.06.23.449675

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