SOLUBLE OLIGOSACCHARIDES AND GALACTOSYL CYCLITOLS IN MATURING SOYBEANSEEDS IN PLANTA AND IN-VITRO

Stachyose, sucrose, and other non-reducing soluble carbohydrates are a ssociated with the onset of desiccation tolerance during seed developm ent and with seed storability. Mature soybean [Glycine mar (L) Merr.] seeds contain several galactosyl cyclitols in addition to sucrose, sta chyose, and raffinose, but except for galactinol, the accumulation of these galactosyl cyclitols has not been reported for developing soybea n seeds. Fifteen soluble carbohydrates including members of the raffin ose, galactinol, galactopinitol, and fagopyritol series were analyzed in extracts from axis and cotyledon tissues of seeds and zygotic embry os matured in planta and in vitro. Galactopinitol A, galactopinitol B, and fagopyritol B1 accumulate in axis tissues of developing soybean s eeds in planta in association with the onset of desiccation tolerance, yellowing of axis tissues, and in parallel with stachyose accumulatio n. Galactopinitol A, galactopinitol B, fagopyritol B1, and stachyose a lso accumulate in parallel in cotyledons in planta and in axis tissues during in vitro growth of zygotic embryos at 15 and 25 degrees C. Axe s of soybean seeds matured at 25 degrees C contained higher concentrat ions of sucrose, raffinose, D-pinitol, D-chiro-inositol, fagopyritol E l, and total soluble carbohydrates than axes of seeds matured at 18 de grees C. Soybean seeds accumulate mostly galactosyl pinitols and only small amounts of free pinitol. In future work, It would be of interest to determine if galactosyl cyclitols may substitute for the role of s tachyose in providing desiccation tolerance and prolonged seed storabi lity.