Time-dependent Changes in the Longitudinal Sugar and Respiratory Profiles of Asparagus Spears During Storage at 0 °C

Abstract

The rate of respiration and the concentrations of sucrose, glucose, and fructose were measured along the length of intact asparagus (Asparagus officinalis cv. Jersey Giant) spears during storage at 0 °C. Carbon dioxide production by each of five sections along the spear was initially high but underwent a rapid and extensive decline within the first 24 hours after harvest with the rate of decline slowing thereafter. The respiration rate was highest at the tip (Section 1), decreasing as the distance from the tip increased (Sections 2 through 5 with Section 5 being more basal). Initially, the respiration rate of the tip was approximately four times that of the base, but after 23 days at 0 °C, the respiration rate of the tip was only twice that of the base. Sugar levels were measured in Sections 1 through 4. Sugar levels declined with time, but increased, unlike respiration, with distance from the tip. Sucrose underwent a rapid decline within the first 24 hours of storage in the tip and Sections 3 and 4. Sucrose depletion was most extensive in the tip, reaching more than 95% by Day 23. Glucose underwent the most rapid decline in Section 2. The relatively higher rate of glucose depletion in Section 2, the zone of rapid cell elongation, may have been to support a relatively higher rate of cell wall biosynthesis in this section. For the first day after harvest, sugar depletion far outstripped hexose equivalents respired as CO2. Afterward, however, the rate of respiration (as hexose equivalents) was similar to the rate of sugar depletion for all sections except the most basipetal, which lost carbohydrate faster than could be accounted for by respired CO2. The data suggest that hexoses were exported from more basipetal tissues to support the metabolic activity of more acropetal sections.