Abstract
The free sugars and starch were determined in the three different parts (cotyledon, hull, and hypocotyl) of the ripening soybean seed. In order to investigate the carbohydrate contents of unripe soybean eaten as a vegetable and the metabolic changes of free sugars and starch during growth.
The soybean, Kyûshû No. 12, was sown in July, 1969, and harvested before the sunrise of every fourth day during the months of September till November. The seeds harvested were separated mechanically into the three parts.
For the determination of free sugars, the sample was extracted with 80% boiling ethanol and then with cold water. The extract was separated by paper chromatography and each sugar extracted with cold water from the respective partition of chromatogram was subjected to the determination by four conventional colorimetric methods. Starch was determined with the glucoamylase and glucose oxidase -peroxidase method.
Free sugar content in hypocotyl was increased up to 44% of total solid matter as a transient phenomenon and decreased in parallel with the growth. The reducing sugar content was 3.5% in the early stage of growth, and it rapidly decreased to a trace. Although reducing sugars, glucose, galactose, fructose, maltose and maltotriose, were detected from the early stage through defoliating stage, only glucose was detected in the latest stage. Nonreducing sugars, sucrose, raffinose and stachyose, were detected through all the stages during growth. In cotyledon, they were gradually detected during growth, i. e., sucrose→raffinose→stachyose→verbascose. In hypocotyl, a high content of starch, nearly 68%, was temporarily determined however, starch content was maintained rather low during growth.
