ASGSB 1999 Annual Meeting Abstracts

EFFECTS OF SUPER-ELEVATED CO₂ CONCENTRATION ON ELECTRON TRANSPORT RATES OF WHEAT GROWN IN CONTROLLED ENVRONMENTAL CHAMBERS. B.C. Durant^1,2, O. Monje², G.W. Stutte², J.A. Guikema¹ and J.E. Leach¹. ¹Plant Biotechnology Center, Kansas State University, Manhattan, KS and ²Dynamac Corporation, Kennedy Space Center, FL.

Photosynthetic electron transport activity is controlled in part by the redox potential of acceptors on the reducing side of photosystem II. Changes in this redox potential directly impact the total fluorescence yield (Fv/Fm), the extent of non-photochemical quenching (qQ), and the extent of photochemical quenching (qE) of the photosynthetic apparatus. Measuring these values, therefore, provides a non-destructive estimate of photosynthetic activity. We used this approach to monitor photosynthesis as a function of CO₂ concentration, since elevated levels are often found aboard spacecraft and consequently may affect the photosynthetic activity of space-grown plants. We monitored the fluorescence parameters at various CO₂ concentrations (400, 1000, 1500, 3000, 5000, and 10,000 mmol mol^-1) of two wheat cultivars (Apogee and Super dwarf) grown in controlled environmental chambers at the Kennedy Space Center. Electron transport rates were estimated from measurements of qE and qQ, which were made using a pulse amplified modulating fluorometer. This non-destructive method may provide a means for assessing the impact of space flight on physiological adaptations of photosynthetic activity to super-elevated levels of CO₂. These measurements were conducted as baseline testing for the Photosynthesis Experiment and System Testing and Operations (PESTO) experiment being developed for the International Space Station.

(Supported by a Kansas NASA-EPSCoR summer fellowship, NASA; NCC10-0027).

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