CHANGES IN SUCROSE SYNTHASE AND SUCROSE PHOSPHATE SYNTHASE ACTIVITIES, AND SUGAR DISTRIBUTION IN AUTUMN-HARVESTED ASPARAGUS

Changes in sucrose synthase (SS), sucrose phosphate synthase (SPS) activities and distribution of sugar content were investigated in asparagus (Asparagus officinalis L. cv. E414 and Green Tower) spears subjected to selected fertilizer treatments applied in the early-harvest (September) and harvesting (October) season. The results suggest that fertilizer application in the early-harvest and harvesting season had no impact on the enzyme activities, sugar distribution and spear weight. In the top portion of the spears in both cultivars, SS activity gradually decreased with time with a concomitant increase in the accumulation of sucrose producing a significant negative correlation. This indicated that in the vigorously growing tissues, as in the top portion of the asparagus spears, SS is responsible for sucrose breakdown. In the bottom portion of the two cultivars, however, SS remained constant. SPS activity remained constant in both portions of the two cultivars. SS and SPS showed higher activities in the bottom than in the top portion of the spear but sucrose content increased gradually with time in both portions of the two cultivars, and fructose concentrations were always higher than glucose.