Performance Assessment of Thermal Infrared Cameras of Different Resolutions to Estimate Tree Water Status from Two Cherry Cultivars: An Alternative to Midday Stem Water Potential and Stomatal Conductance

The midday stem water potential (&Psi
s) and stomatal conductance (gs) have been traditionally used to monitor the water status of cherry trees (Prunus avium L.). Due to the complexity of direct measurement, the use of infrared thermography has been proposed as an alternative. This study compares &Psi
s and gs against crop water stress indexes (CWSI) calculated from thermal infrared (TIR) data from high-resolution (HR) and low-resolution (LR) cameras for two cherry tree cultivars: &lsquo
Regina&rsquo
and &lsquo
Sweetheart&rsquo
For this purpose, a water stress&ndash
recovery cycle experiment was carried out at the post-harvest period in a commercial drip-irrigated cherry tree orchard under three irrigation treatments based on &Psi
s levels. The water status of trees was measured weekly using &Psi
s, gs, and compared to CWSIs, computed from both thermal cameras. Results showed that the accuracy in the estimation of CWSIs was not statistically significant when comparing both cameras for the representation of &Psi
s and gs in both cultivars. The performance of all evaluated physiological indicators presented similar trends for both cultivars, and the averaged differences between CWSI&rsquo
s from both cameras were 11 &plusmn
0.27%. However, these CWSI&rsquo
s were not able to detect differences among irrigation treatments as compared to &Psi
s and gs.