The seasonal variations in inulin and reducing sugar in Jerusalem artichoke 'KKU 50-4'

摘要

The objective of this study was to compare the effect of different planting seasons on contents and storage rates of inulin and reducing sugar in Jerusalem artichoke (JA) 'KKU 50-4'. JA was transplanted in December 2013, January, February, March and April 2014. Leaves, stems, roots and tubers were harvested at 20, 40, 60 and 80 days after transplanting (DAT) and harvesting stage for determining contents and storage rate of inulin and reducing sugar. The results showed that the highest inulin contentwas found in roots and tubers of the plants belonging to the April planting date at 40 DAT. At later stages the inulin content in tubers was drastically declining until the harvesting stage. Similar pattern of changes in inulin content during plant development was also observed in plants of the other planting dates. Reducing sugar content in tubers was increasing from the early growth stage to harvesting stage. This pattern of reducing sugar accumulation in tubers was observed for plants of all plantingdates. The highest reducing sugar content was found at harvesting stage in tubers of the plants belonging to the December 2013 planting date. In contrast, reducing sugar contents in leaves, stems and roots were high at the earlier growth stage and slightly decreased at harvesting stage. This pattern of changes in reducing sugar in leaves, stems and roots was similar for plants which were transplanted in different months. This result suggested that there was translocation of reducing sugar from leaves,stems and roots to tubers during harvesting stage, especially for those planted in December. Therefore, highest inulin content could be obtained from JA transplanted in April and harvested at 40 DAT while highest reducing sugar was found at harvesting stage in JA transplanted in December.