ISHS Acta Horticulturae 537: III International Symposium on Irrigation of Horticultural Crops
POTENTIAL USE OF INFRA-RED THERMOMETRY FOR THE DETECTION OF WATER STRESS IN APPLE TREES |
| Authors: | R. Giuliani, J.A. Flore |
| Keywords: | Canopy surface temperature, digital-image processing and analysis, leaf gas exchange, remote sensing, water deficit. |
| Abstract:
Ground-based IR thermometry was used to estimate canopy surface temperature of apple trees, with the aim of early detection of water stress. The study was carried out in Michigan during the summer of 1998 in a four-year-old apple orchard. Digital thermo-images (thermograms) of the canopy were acquired using an IR imaging radiometer on well-watered trees and trees subjected to water deficit. Environmental (air and soil) variables were also monitored. The protocol followed in our research made it possible to compare thermograms acquired in the two experimental situations. A custom-written program was used to process the digital images, display the thermal frequency distribution and estimate the parameters identifying the physiological state of the observed canopies. Unirrigated plants showed generally higher values of central tendency temperature (mainly due to the lower transpiration activity that affects leaf energy budget) and different shape parameters (skewness and kurtosis) of thermal distribution, as compared to those of well-watered plants. These changes were detected even though physiological responses, such as photosynthetic activity and fruit growth, were not yet adversely affected by water stress. The study confirms that there is a theoretical basis for the use of IR thermometry and digital-image processing to detect rapidly plant water deficit in the field and potentially to timely decide the need for irrigation. | |
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