Abstract
The midday stem water potential (Ψs) 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 Ψs 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: ‘Regina’ and ‘Sweetheart’. For this purpose, a water stress–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 Ψs levels. The water status of trees was measured weekly using Ψs, 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 Ψs and gs in both cultivars. The performance of all evaluated physiological indicators presented similar trends for both cultivars, and the averaged differences between CWSI’s from both cameras were 11 ± 0.27%. However, these CWSI’s were not able to detect differences among irrigation treatments as compared to Ψs and gs.
Highlights
Sweet cherry (Prunus avium L.) is a high-value fruit in the Southern Hemisphere fruticulture since they are of high demand fresh fruits in Northern Hemisphere markets [1]
Fruit growers are applying irrigation strategies to increase water use efficiency (WUE) and water productivity (WP), such as regulated deficit irrigation (RDI) to reduce the amount of water irrigated during the growing season and obtain certain benefits such as improving water productivity [3,4,5]
The gc is normally estimated from leaf-based measurements of stomatal conductance using hand-held porometers or gas exchange instruments to be scaled to the whole canopy using the leaf area index (LAI) [13]
Summary
Sweet cherry (Prunus avium L.) is a high-value fruit in the Southern Hemisphere fruticulture since they are of high demand fresh fruits in Northern Hemisphere markets [1]. Examples of the application of Ψs for managing the irrigation of ‘Summit’ [10], ‘Prime Giant’ [8], and ‘Sweetheart’ sweet cherry trees [12], showed that a moderate post-harvest RDI treatment does not produce any detrimental effect on fruit yield and quality, substantially reducing the total water irrigated. Another sensitive physiological parameter to water stress is canopy conductance (gc), which represents the average leaf conductance of the whole canopy. The latter characteristics make it difficult to use them for continuous measurements or automated monitoring of plant water stress to obtain a high temporal and spatial resolution and to account for the natural variability of orchards [13,14]
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