|Crop Physiology and Agronomy|
My graduate research at Texas A&M University, working with C.H.M. van Bavel, focused on water transport in root systems exposed to large differences in water potential. Using a traveling gamma densitometry system, we were able to measure simultaneous water uptake in moist regions of the root zone and exudation in drier zones, in both bermudagrass and cotton (Baker & Van Bavel, 1986; Van Bavel & Baker, 1986). This transfer of water, subsequently referred to by Richards & Caldwell as hydraulic lift, has since become a widely studied phenomenon. While pursuing this research, my fellow graduate student, Atsushi Kano, made me aware of some interesting work being done in Japan by Sakuratani on the measurement of sap flow in plants. I contacted Dr. Sakuratani, who graciously provided me with a few of his stem gauges [see photo below]. I tested them and found that they worked, but were far too fragile for extended field use, and were limited by their manganin wire heaters, which burned out rather quickly. I spent several months redesigning the gauges to develop a unit suitable for field research. I used a flexible kapton heater, originally designed for satellite valves, and encased the entire unit in flexible foam pipe insulation [see photo below]. This resulted in a rugged, yet accurate unit which I used for measuring cotton transpiration in my dissertation research(Baker, 1987; Baker & Van Bavel, Plant Cell Env. 1987). This gauge design was subsequently commercialized by Dynamax and is now widely used by plant physiologists around the world.