Are Raffinose and Stachyose Unloaded from Soybean Seed Coats toDeveloping Embryos?

摘要

During soybean [Glycine max (L.) Merrill] seed development, seed coat tissues contain sucrose, myo-inositol,D-chiro-inositol, D-pinitol and low concentrations of galactinol. Low concentrations of fagopyritol B1, galactopinitols, andraffinose also accumulate in seed coats during mid-maturation and stachyose accumulates late in maturation. Traces ofraffinose can be detected in cotyledons of young seeds (24 days after pollination) and infrequently in seed coat cupexudates at mid-seed fill. On gas chromatograms, questionable peaks corresponding to the retention time of raffinose maybe observed in seed coat cup exudates. To determine if raffinose and stachyose can be unloaded from seed coats into thefree space surrounding developing seeds, soybean stem-leaf-pod explants from plants with low-raffinose, low-stachyoseseeds (LRS) or normal raffinose and stachyose seeds (CHECK) were fed solutions containing 10 mM raffinose or 10 mMstachyose via the cut stem for 3 days. Raffinose was present in leaf, pod and seed coat tissues after feeding raffinose orstachyose to explants. Small amounts of raffinose were unloaded into seed coat cups. Stachyose accumulated in leaf andpod tissues after feeding stachyose to explants, but stachyose was detected in only one of the 32 seed coat exudatesassayed. Soybean seed coats unloaded raffinose in very small amounts that may explain the presence of trace amounts ofraffinose in embryo tissues of young seeds.