Remote Measurement of Plant Stress: A Look Back in Time.

The U.S. Water Conservation Laboratory in Phoenix, Arizona (constructed in 1958) was tasked to study water conditions in the arid Southwest.  In doing so, both engineering and soil-plant-atmosphere interactions were explored. The latter of these two charges was the task of the lab's Soil, Plant, Atmosphere (SPA) Group, which utilized infrared (IR) thermometry to assess plant water stress.  Early on, its scientists found that the initial models of IR instruments were overly sensitive to ambient temperature. This and other aspects of the SPA Group's research will be discussed.