407 Regulation of Carbon Flux as a Function of O2 and CO2 Atmospheres in Asparagus Tips

Abstract

The purpose of this work was to investigate the influence of O2 and CO2 partial pressures on glycolytic carbon flux, phosphorylated intermediates, phosphate, pyrophosphate, and phosporylated nucleotides in asparagus spears tips stores at 1 °C. The effects of CO2 (0, 5, 10, and 20 kPa) combined with O2 pressures ranging from 0.1 to 16 kPa (1% O2 = 1.013 kPa O2 at 1 atm) were investigated. Spears were enclosed within a low-density polyethylene (LDPE) package (for the 5-, 10-, and 20-kPa CO2 treatments) having a surface area of 462 cm2 and enclosed in 1.95-L glass jars. Low O2 enhanced the interconversion of phosphoenolpyruvate (PEP) to pyruvate (PYR) and F6P to F1,6P2 relative to high O2. When spears tips at 16 kPa O2 were compared to those at harvest, little change occurred in the adenylate or phosphate pools. PPi and ATP contents decreased as the O2 partial pressure declined below 16 kPa O2. In general, as CO2 increased, PPi and ATP decreased, while Pi, ADP, and AMP increased. The adenylate energy charge (AEC) declined with a decline in the O2 partial pressure, declining most rapidly below 2 kPa O2. Low O2 reduced AEC relative to high O2. Increasing CO2 partial pressure reduced AEC, an effect not evident at lower O2. The data suggest low O2 and elevated CO2 impair oxidative phosphorylation and induce nonsustaining carbon metabolism, which may limit asparagus spear survival under O2-deficient conditions.