Plant Biosensors Analysis for Monitoring Nectarine Water Status.

The real-time monitoring of plant water status is an important issue for digital irrigation to increase water productivity. This work focused on a comparison of three biosensors that continuously evaluate plant water status: trunk microtensiometers (MTs), trunk time-domain reflectometry (TDR), and LVDT sensors. During the summer and autumn seasons (DOY 150–300), nectarine trees were subjected to four different consecutive irrigation periods based on the soil Management Allowed Deficit (MAD) concept, namely: MAD₁₀ (light deficit); MAD₅₀ (moderate deficit); MAD₁₀₀ (severe deficit), and MAD₀ (full irrigation). Measurements of stem water potential (Ψ_stem) and leaf gas exchange were recorded on representative days. A continuous measurement of the plant water status of Ψ_trunk, MDS, and K_trunk revealed the water deficits imposed on the soil. The highest water deficit observed at the end of the MAD₁₀₀ period (Ψ_stem = −2.04 MPa and Ɵ_v = 17%) resulted in a minimum value of Ψ_trunk (−1.81 MPa). The maximum value of MDS (408 µm) was observed earlier than that of Ψ_trunk, motivated by the low sensitivity of MDS at Ψ_trunk < −1.2 MPa and Ψ_stem < −1.5 MPa due to a decrease in the tissue elasticity of the trunk when severe water deficit conditions are reached. Both Ψ_trunk and Ψ_stem were more dependent on soil water content, while MDS was more responsive to environmental changes. K_trunk was the weakest indicator for determining plant water status, although when expressed as a daily fraction of depletion (K_trunkFD), it improved, evidencing a process of hysteresis. Ψ_trunk showed the highest sensitivity, suggesting the potential use of MTs as a valuable biosensor for monitoring nectarine water status in digital agrosystems. [ABSTRACT FROM AUTHOR]