柑橘果实糖积累与蔗糖代谢酶活性的研究

Sugar Accumulation and Changes of Sucrose-metabolizing Enzyme Activities in Citrus Fruit

研究了脐橙、柠檬果实发育过程中汁胞和果皮内糖含量与糖代谢酶活性的变化。结果表明 :不同柑橘品种、不同部位糖积累和相关酶活性变化不同。柑橘汁胞和果皮中还原糖含量均高于蔗糖含量。随着脐橙汁胞中糖分的积累 ,酸性转化酶 (SAI)活性持续下降 ,至采收时几乎为零 ,说明SAI的下降与脐橙汁胞糖分积累有很大关系。柠檬汁胞中的中性转化酶 (NI)活性随着果实成熟而下降 ,在成熟时保持极低水平 ,而此时SAI活性则较高 ,是其它酶活性的 6倍以上 ,表明柠檬汁胞中糖分的利用在果实成熟前与NI活性有极大的关系 ,在成熟期则与高SAI活性有关。脐橙和柠檬汁胞间糖组分的明显差异和相关酶的变化动态表明蔗糖合成酶 (SS)

Sugar contents and activities of sugar metabolizing enzymes in the peel and juice sacs were analyzed during the fruit development of Newhall orange( Citrus sinensis Osb.)and Eureka lemon( C.limon Burm.f.).The results showed that,1)changes of the sugar contents and activities of sugar metabolizing enzymes were different in citrus cultivars and in different fruit parts;2)the reduction sugar content was higher than the sucrose content in both peel and juice sacs of orange or lemon,as was different from other's study;3)the continuous decrease of the soluble acid invertase(SAI)activity during sugar accumulation of orange juice sacs,close to zero at the fruit harvesting time,implicated that the decline of SAI activity was likely related to sugar accumulation;and 4)the phenomena that the activity of the alkaline invertase(NI)in lemon juice sacs decreased continuously with fruit ripeness and kept the lowest level at the fruit harvesting time while as the activity of SAI reached a higher level,up to 6 times of that of the other enzymes,indicated that the consumption of sugars in lemon juice sacs was related to NI activities during the fruit developmental stages and to SAI at fruit maturing period.Sucrose synthase(SS)and invertase might play a role in sucrose metabolism in citrus fruit juice sacs considering the significant difference of sugar contents between in orange and lemon juice sacs as well as the changes of their related sucrose metabolizing enzymes.