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Title: PHOTOSYNTHESIS, CHLOROPHYLL FLUORESCENCE AND YIELD OF SNAP BEAN (PHASEOLUS VULGARIS L.) GENOTYPES DIFFERING IN SENSITIVITY TO OZONE

Author
item Flowers, Michael
item Fiscus, Edwin
item Burkey, Kent
item Booker, Fitzgerald
item Dubois, Jean Jacques

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2007
Publication Date: 11/1/2007
Citation: Flowers, M.D., Fiscus, E.L., Burkey, K.O., Booker, F.L., Dubois, J.B. 2007. Photosynthesis, chlorophyll fluorescence and yield of snap bean (phaseolus vulgaris l.) genotypes differing in sensitivity ozones. Environmental and Experimental Botany. 61:190-198.

Interpretive Summary: Air pollution is a growing concern in agricultural production. A study was conducted to determine the effects of the pollutant ozone on snap bean (Phaseolus vulgaris L.). Three snap bean genotypes with known differences in their tolerance to ozone were grown under controlled conditions in a replicated experiment. Weekly measurements of photosynthetic mechanisms were taken throughout the growing season. Snap bean yield was determined at the end of the growing season. Ozone reduced the yield of all three genotypes. Yield reduction was greatest in the most sensitive genotype. Ozone also reduced photosynthesis in the most sensitive genotype. Photosynthesis in the two tolerant genotypes was not affected by ozone. Thus, further research is required to determine the reason both yield and photosynthesis vary between snap bean genotypes when exposed to ozone.

Technical Abstract: The impact of phytotoxic pollutants such as ozone (O3) is a concern for agricultural production. This study was undertaken to study the effects of O3 on three snap bean (Phaseolus vulgaris L.) genotypes with known differences in their tolerances to O3. Snap beans were grown in environmentally controlled field chambers in which temperature, relative humidity, and O3 were controlled and admitting 90% of full daily sunlight. A 4 x 3 factorial design with four O3 treatments and three snap bean genotypes was used. Measurements of photosynthesis and chlorophyll fluorescence were made weekly throughout the growing season. Yield data was collected at physiological maturity. The effects of O3 on the yield and photosynthetic parameters varied greatly depending on the genotype and O3 concentration. A low concentration of O3 (15 nmol mol-1) was found to increase the yield of two of the three snap bean genotypes compared to the no O3 control. However, the highest O3 concentration (60 nmol mol-1) significantly reduced the yield in all three snap bean genotypes. The effect of O3 on the photosynthetic parameters of the three genotypes also differed greatly. Ozone reduced the photosynthetic capacity and disrupted electron transport in the most susceptible genotype (S156). However, the two tolerant snap bean genotypes (R123 and R331) did not show an effect on either the photosynthetic capacity or electron transport due to O3. These genotypes did however show reduced yield in the high O3 treatment (60 nmol mol-1). These yield differences are most likely due to a decrease in assimilate translocation from the leaf to reproductive tissues.