Assessment of trunk microtensiometer as a novel biosensor to continuously monitor plant water status in nectarine trees

Abstract

The objective of this work was to validate the trunk water potential (Ψ_trunk), using emerged microtensiometer devices, as a potential biosensor to ascertain plant water status in field-grown nectarine trees. During the summer of 2022, trees were subjected to different irrigation protocols based on maximum allowed depletion (MAD), automatically managed by real-time soil water content values measured by capacitance probes. Three percentages of depletion of available soil water (α) were imposed: (i) α=10% (MAD=27.5%); (ii) α=50% (MAD=21.5%); and (iii) α=100%, no-irrigation until Ψ_stem reached -2.0 MPa. Thereafter, irrigation was recovered to the maximum water requirement of the crop. Seasonal and diurnal patterns of indicators of water status in the soil-plant-atmosphere continuum (SPAC) were characterised, including air and soil water potentials, pressure chamber-derived stem (Ψ_stem) and leaf (Ψ_leaf) water potentials, and leaf gas exchange, together with Ψ_trunk. Continuous measurements of Ψ_trunk served as a promising indicator to determine plant water status. There was a strong linear relationship between Ψ_trunk vs. Ψ_stem (R² = 0.86, p<0.001), while it was not significant between Ψ_trunk vs. Ψ_leaf (R² = 0.37, p>0.05). A mean gradient of 0.3 and 1.8 MPa was observed between Ψ_trunk vs.Ψ_stem and Ψ_leaf, respectively. In addition, Ψ_trunk was the best matched to the soil matric potential. The main finding of this work points to the potential use of trunk microtensiometer as a valuable biosensor for monitoring the water status of nectarine trees. Also, trunk water potential agreed with the automated soil-based irrigation protocols implemented.

Keywords: Prunus persica (L); SPAC; automated irrigation; stem water potential; trunk water potential.