A Comparison of Plant Temperatures as Measured by Thermal Imaging and Infrared Thermometry

The temperature of leaves and canopies of plants has long been recognised to be an indicator of plant water stress and can be assessed by thermometry or thermography. Considerable research has been carried out with each of these techniques individually; however, a comparable assessment has not been done to the best of our knowledge. Therefore, we compared the potential of high-resolution thermography and infrared (IR) thermometry to discriminate among stress treatments (control, drought, salt and combined salt and drought) and cultivar effects in large container-based experiments that mimicked field conditions. Differences among treatments and between cultivars, with differences varying between 1-9 and 0-2°C, respectively, were in dense crop stands comparably well ascertained by IR thermometry and thermography. Both methods allowed discriminating differences in salt tolerance. Interestingly, enough similar results were observed for processed, by unmixing the soil influence, and unprocessed thermal images at soil coverage higher than 60%. Using thermography and IR thermometry, highly significant and close relationships were established between canopy temperature and leaf water potential. Overall, in this study, the more simplistic technique based on IR thermometry performed in dense crop stands similarly well as the more sophisticated method provided by thermography.