Soluble carbohydrates in soybean seeds during development and imbibition

Soybean (Glycine max [L.] Merr.) seed soluble carbohydrates include sugars and cyclitols, but the biological role of the latter in plant development i s poorly understood, particularly during seed imbibition. This study examin ed the relationship between sugars and cyclitols during seed development un der field conditions and imbibition. Twelve soluble carbohydrates (includin g reducing sugars, sucrose, raffinose saccharides, free cyclitols and galac tosyl cyclitols) were determined in soybean axes and cotyledons at five see d development (8, 90, 173, 265, and 220 mg seed(-1)) and six imbibition (4, 8, 12, 16, 20, and 24 hours post imbibition) stages. Extraction and deriva tization were simultaneously performed in a solution of a pyridine-based re agent followed by separation in a gas chromatograph. Soluble carbohydrate c oncentration was significantly higher in axes than cotyledons at all stages of seed development and imbibition. In both the axes and cotyledons, reduc ing sugars and free cyclitols decreased, while sucrose, raffinose saccharid es and galactosyl cyclitols accumulated with seed development. During imbib ition, sucrose, raffinose saccharides and galactosyl cyclitols were degrade d and an accumulation of reducing sugars and free cyclitols was observed. T he positive correlation between raffinose saccharides and galactosyl cyclit ols during soybean seed development and imbibition may provide a basis for understanding their physiological and/or biochemical roles in relation to s oybean quality. For example, increasing galactosyl cyclitol levels and decr easing raffinose saccharide levels in maturing soybean seeds might contribu te to the development of desiccation-tolerant soybean cultivars, without th e flatulence associated with high levels of raffinose saccharides.