比较了甜种、荸荠种和冰糖种白肉枇杷以及宝珠、大叶杨墩和大玫瑰红袍红肉枇杷成熟果实果肉的可溶性糖含量、组成及蔗糖代谢相关酶活性的差异。结果显示白肉枇杷果肉可溶性总糖含量高于红肉枇杷,且以蔗糖为主(占60%~70%),其次是果糖(20%~30%)和葡萄糖(9%~11%),而红肉枇杷中3种可溶性糖的含量比较接近。白肉枇杷果肉蔗糖占总糖的比例显著高于红肉枇杷,而葡萄糖则相反,但果糖占总糖的比例在2类枇杷中比较接近。白肉枇杷果实中性转化酶(NI)、酸性转化酶(AI)、蔗糖合成酶合成方向(SUS-synthetic)和蔗糖合成酶分解方向(SUS-cleavage)活性均低于红肉枇杷,蔗糖磷酸合成酶(SPS)活性则比较接近。2类枇杷果肉蔗糖代谢酶的净活性均为负值,但红肉枇杷酶的净活性较低。研究认为,蔗糖代谢酶活性与2类枇杷果肉可溶性糖含量和组成差异存在密切关系。
White-fleshed loquat cultivars Tianzhong,Biqizhong and Bingtangzhong as well as red-fleshed loquat cultivars Baozhu, Dayeyangdun and Dameiguihongpao were used to study the sugar composition difference between white- and red-fleshed loquat flesh and its relation with activities of sucrose-metabolizing enzymes. The results showed that total soluble sugar content of white-fleshed loquats was higher than that of red-fleshed ones, with the highest found in Tianzhong and Bingtangzhong; sucrose was the major sugar in white-fleshed loquats (60% to 70%), followed by fructose (20% to 30%) and glucose (9% to 11%), while the content of these sugars were similar in red-fleshed fruits. Percentage of sucrose among total soluble sugars was significantly higher in white-fleshed fruits than in red-fleshed ones, while percentage of glucose was on the contrary, and that of fructose was similar. Activities of NI, AI, SUS-synthetic and SUS-cleavage were higher in red-fleshed loquat fruits, and that of SPS was similar in two fruit groups. Net activity of sucrose-metabolizing enzymes was negative in both loquat groups, but was lower in red-fleshed ones. The data suggested that the activities of sucrose-metabolizing enzymes were closely related to the difference in soluble sugar accumulation and composition between two loquat groups.