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A Nanomaterial Sensor for Monitoring H2O2 in Plants Grown in Low Atmospheric Pressure. M.J. Correll1, H.J. Cho2, S. Seal3, A Mehta2, S. Patil3, R.A. Bucklin1. 1Agricultural and Bio. Engineering Dept., Univ. of Florida, Gainesville, FL. 2MMAE Dept., 3AMPAC/MMAE Dept., Univ. of Central Florida

     In plant and animal cells, hydrogen peroxide (H2O2) is an important signaling molecule that controls many aspects of normal cellular metabolism. H2O2 is also produced in cells in response to stress conditions and excessive amounts can result in oxidative damage and death of cells or whole tissues. During spaceflight (and in future Mars or Moon greenhouses) plants are exposed to a variety of stress conditions which can result in overproduction of H2O2 and result in crop loss. Therefore, characterization of H2O2 levels in plants grown in stress conditions on earth will aid in designing growth chambers and developing procedures to reduce the stress conditions of plants grown on space missions. Current methods for measuring H2O2, such as enzymatic reactions and biochemical assays, are time-consuming, destructive to plant tissues, expensive, and often require several steps during sample preparation before the H2O2 measurements are recorded. To address these problems, we have developed a nanomaterial-integrated probe to measure H2O2 in cells and cell extracts from plants.  This probe uses unique properties of the nanomaterial (ceria) to monitor H2O2 levels and has long-term stability, reproducibility, and is renewable. Preliminary results from the probe indicate that H2O2 levels in leaf extracts are greater than those measured using traditional H2O2 detection techniques (i.e., Amplex Red assay, Molecular Probes, OR). For example, results from the probe measured immediately after grinding leaf tissues in liquid nitrogen and resuspending the cell extract in H2O was 5 times the levels of H2O2 measured with traditional assays (1 vs. 0.2 mmol H2O2 g-1 of fresh weight, respectively). The lower levels of H2O2 found with the enzymatic measurements is likely due to the extensive sample processing (including column chromatography) which results in H2O2 degradation. Studies to monitor H2O2 production in tomatoes grown in a low atmospheric pressure greenhouse are currently being performed. (Support by UCF FL Space Grant; SPACE INIT 2004-2005).