Relating microtensiometer-based trunk water potential with sap flow, canopy temperature, and trunk and fruit diameter variations for irrigated 'Honeycrisp' apple

Blanco, Victor , Kalcsits, Lee

2024-05-24 FRONTIERS IN PLANT SCIENCE 2024   15(卷), null(期), (null页)

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Instrumentation plays a key role in modern horticulture. Thus, the microtensiomenter, a new plant-based sensor that continuously monitors trunk water potential (Psi trunk) can help in irrigation management decisions. To compare the response of the Psi trunk with other continuous tree water status indicators such as the sap flow rate, the difference between canopy and air temperatures, or the variations of the trunk and fruit diameter, all the sensors were installed in 2022 in a commercial orchard of 'Honeycrisp' apple trees with M.9 rootstocks in Washinton State (USA). From the daily evolution of the Psi trunk, five indicators were considered: predawn, midday, minimum, daily mean, and daily range (the difference between the daily maximum and minimum values). The daily range of Psi trunk was the most linked to the maximum daily shrinkage (MDS; R2 = 0.42), the canopy-to-air temperature (Tc-Ta; R2 = 0.32), and the sap flow rate (SF; R2 = 0.30). On the other hand, the relative fruit growth rate (FRGR) was more related to the minimum Psi trunk (R2 = 0.33) and the daily mean Psi trunk (R2 = 0.32) than to the daily range of Psi trunk. All indicators derived from Psi trunk identified changes in tree water status after each irrigation event and had low coefficients of variation and high sensitivity. These results encourage Psi trunk as a promising candidate for continuous monitoring of tree water status, however, more research is needed to better relate these measures with other widely studied plant-based indicators and identify good combinations of sensors and threshold values.