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PESTO GROUND CONTROL EXPERIMENTS:  A GAS EXCHANGE SYSTEM FOR MEASURING PHOTOSYNTHESIS AND EVAPOTRANSPIRATION.   T. T. Tran¹, O. Monje², and G.W. Stutte². ¹University of Illinois, Urbana, IL ²Dynamac Corporation, Kennedy Space Center, FL.

The PESTO (Photosynthesis Experiment System and Testing and Operation) spaceflight experiment aims to measure photosynthesis and transpiration in microgravity. A four-chamber gas exchange system was designed, programmed, and assembled for conducting PESTO ground control experiments. The gas exchange system will measure ground-based data to be used for comparison with microgravity-based data obtained in the BPS (Biomass Production System, Orbitec, Madison, WI) aboard the International Space Station. The gas exchange system consists of a mixing tank, a plant growth chamber, mass flow meters, and two infrared analyzers to measure the CO₂/H₂O concentrations. The mixing tank allows the concentration of CO₂ to be varied between 300 to 2000 mmol/mol with +/- 10 mmol/mol accuracy. The mass flow of air into the chambers ranged between 2-8 Liters per min. CO₂ recovery tests and measurements of chamber leak rates were performed. In addition, relative measures of net photosynthesis and transpiration of wheat canopies grown at 3 different water potentials were made using the gas exchange system. These measurements agreed with measures of net assimilation rate and leaf area index obtained from growth analysis data.

(This work was supported in part by NASA’s Fundamental Biology Program (NCC-0034) and Spaceflight and Life Sciences Training Program.)