Infrared thermal sensing of plant canopies as a screening technique for dehydration avoidance in wheat

Abstract

Remote sensing research indicates that leaf-canopy temperatures are related to plant water stress. Leaf-canopy temperatures can be rapidly monitored remotely by the IR thermometer. Ground-level IR sensed leaf-canopy temperatures were evaluated as a fast comparative assay of dehydration avoidance (maintenance of higher leaf water potential) in wheat breeding materials, subjected to soil moisture stress. In three separate field tests, during a period of moisture stress, midday temperatures of fully developed plant canopies were correlated with leaf water potentials across various wheat strains. Lower canopy temperatures were indicative of higher leaf water potentials. Correlation coefficients became larger and more significant as streess progressed. In one test, where sufficient data were available, leaf temperature was also significantly and positively correlated with leaf diffusive resistance, across strains. While site (and instrument) variation in leaf temperatures, as measured across replicated plots of a given genotype, ranged within about 1–2°C, extreme differences among various genetic materials ranged within 4–8°C, with an LSD of 1.1 – 1.9°C, depending on the test and stress intensity. If non-replicated tests were used, the resolution of genetic differences in leaf temperatures was improved by transforming temperature measurements to the percentage of a replicated check cultivar.