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ARS Home Midwest Area St. Paul, Minnesota Soil and Water Management Research People John Baker





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Crop Physiology and Agronomyheadline bar **Hydraulic Lift**My graduate research at Texas A&M University 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; Baker & Van Bavel, 1988). This transfer of water, subsequently referred to by Richards & Caldwell as hydraulic lift, has since become a widely studied phenomenon.**Sap Flow Measurement**While I was at Texas A&M, my officemate and 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 on left]. 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 on right]. This resulted in a rugged, yet accurate unit which I used for measuring cotton transpiration in my dissertation research (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. ****


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