Changes in sucrose synthase and sucrose phosphate synthase activities, andsugar distribution in autumn-harvested asparagus

Changes in sucrose synthase (SS), sucrose phosphate synthase (SPS) activiti es and distribution of sugar content were investigated in asparagus (Aspara gus officinalis L. cv. E414 and Green Tower) spears subjected to selected f ertilizer treatments applied in the early-harvest (September) and harvestin g (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 b oth cultivars, SS activity gradually decreased with time with a concomitant increase in the accumulation of sucrose producing a significant negative c orrelation. This indicated that in the vigorously growing tissues, as in th e top portion of the asparagus spears, SS is responsible for sucrose breakd own. In the bottom portion of the two cultivars, however, SS remained const ant. 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 o f the spear but sucrose content increased gradually with time in both porti ons of the two cultivars, and fructose concentrations were always higher th an glucose.