The response of strawberry fruit exposed to high carbon dioxide conditions-in vivo activities of pyruvate decarboxylase and alcohol dehydrogenase
R. van Gorsel , W.M. Yates , M. Ponce-Valadez , M. Erkan , 0C.B. Watkins
Dept. of Horticulture, Cornell Univ., USA, Dept. of Horticulture, Akdeniz Univ., Antalya, Turkey
2002
บทคัดย่อ
Some strawberry cultivars respond to high (15-30 kPa) CO2 partial pressures with acetaldehyde and ethanol production whereas others respond with succinate accumulation. We are testing the hypothesis that these varietal differences relate to differences in the in vivo activities of pyruvate decarboxylase and alcohol dehydrogenase. These enzymes could affect the amount of pyruvate that is diverted from the tricarboxylic acid (TCA) to the anaerobic fermentation pathway. Strawberry cultivars with known differences in the accumulation of intermediates of the anaerobic metabolic pathway were exposed for up to nine days at 2 0C to atmospheres with either 0, 15 or 30 kPa carbon dioxide in the presence of 20 kPa oxygen in a flow through system. At regular intervals, container inlets and outlets were closed for up to five hours to determine oxygen consumption and carbon dioxide emission and to sample the headspace for volatiles. The direct sampling of headspace volatiles followed by immediate dolumn injection allowed for the determination of the emission rates of acetadehyde, ethyl acetate and ethanol. Comparison of these rates with the volatile contents of replicates of fruits that were frozen after either six or nine days of treatment is making it possible to estimate the in vivo activities of pyruvate decarboxylase and alcohol dehydrogenase. These results will be presented in relation to other differences in metabolic respones of the cultivars to high CO2.