Time-Dependent Changes In the Longitudinal Sugar and Respiratory Profiles of Asparagus Spears During Storage At 0 o C

The rate of respiration and the concentration of sucrose, glucose, and fructose were measured along the length of intact asparagus (Asparagus officinalis L. cv. Giant Jersey) spears during 23 d of storage at 0 ^oC.  The respiration rate was highest at the tip (section 1), decreasing as the distance from the tip increased (section 2 through 5, with the section 5 being more basal). Sugar levels were measured in sections 1 through 4.  Sugar content was lowest at the tip and increased, unlike respiration, with distance from the tip.  Sugar content in each segment declined with time. We calculated the difference in the flux in hexose equivalents between sugar loss and that of respiration in the different segments over time. Positive number indicates carbon flux via sugar depletion to be greater than that accounted for by respiratory losses and suggests net translocation of sugars out of that segment or reallocation of sugars to structural (non-respiratory) uses. Negative numbers suggest alternative (non-sugar) carbon supplies such as proteins and lipids are being used for respiration or that sugar translocation into the tissue occurs. Hexose consumption was positive for all segments during the first day of storage and ranged from 301.5 pmoles·g^-1·s^-1 to 774.4 pmoles·g^-1·s^-1 for section 1 (tip) and section 3, respectively. These high initial rates of hexose consumption are directly related to the high initial hexose levels in all section. Hexose consumption declined dramatically during the next 6 days of storage and ranged from -11.0 to -14.5 pmoles g^-1.s^-1 in the tip and section 2, respectively. In segment 3 and 4, hexose consumption between day 1 and 7 was 0.7 and 41.1 pmoles·g^-1·s^-1, respectively. Taken together with our data on sucrose, glucose and fructose levels these observations support the contention that significant amounts of hexoses are used in processes other than respiration including carbon relocation and possibly cell wall biosynthesis. In support of carbon relocation and/or cell wall biosynthesis it can be noted that the basal section 4 underwent greater carbon loss through hexose depletion than respiration, closely followed by section 3.