Sensing High Speed Response of Plants to Transient Water Stress

Direct measurements of plant properties are typically conducted over days or weeks. This work demonstrates for the first time in the literature (to the best of knowledge) a direct measurement of changes in leaf temperature (due to water stress at the roots), with time scales of minutes or hours. The sensitivity to local temperature changes is approximately 0.001° C and is made possible by direct measurement and amplification of the temperature difference across two thermistors. This is in sharp contrast to prior art, which uses the mathematical difference between two sequential digital measurements or a single measurement and thus, is limited by the resolution of the employed analog-to-digital conversion (ADC). This method based on amplification and sampling of voltage differences, greatly enhances the effective sensitivity even with low-resolution ADCs. As a result, ET is revealed through near immediate temperature increases at the leaf (within minutes), due to water shortage at the roots.