OLIGOSACCHARIDES AND GALACTOSYL CYCLITOLS IN SEED DESICCATION TOLERANCE

Soluble carbohydrates are one of multiple components required for the acquisition of desiccation tolerance during seed development and matur ation. Sucrose and the raffinose series of oligosaccharides have been extensively studied in relation to seed desiccation tolerance. These g alactosyl sucrose oligosaccharides are present in viable tissues of ma ny edible seeds, especially the legumes, and contribute to flatulence after ingestion. A reduction in oligosaccharides of the raffinose seri es is desired by nutritionists but, if present at less than a threshol d level, this this may result in reduced desiccation tolerance and sto rability of seeds. Some seeds that have very low amounts of raffinose and stachyose accumulate galactosyl cyclitols and small amounts of fre e cyclitols. Galactosyl cyclitols present in various seeds include gal actosyl or methyl derivatives of myo-inositol, D-pinitol, D-chiro-inos itol, D-ononitol, and scyllo-inositol. Castor bean seeds accumulate ga lactinol and buckwheat seeds accumulate fagopyritol in addition to suc rose. Fagopyritol accumulation is associated with the acquisition of d esiccation tolerance in buckwheat seeds. The galactosyl sucrose and ga lactosyl cyclitol soluble carbohydrates in maturing seeds have been pr oposed to have various roles in desiccation tolerance including non-to xic and non-reducing forms of seed storage products and intracellular osmotic agents contributing to the structural stability of organelles, membranes, enzymes and proteins, other macromolecules, and the glassy state. Ether derivatives of cyclitols may form liquid crystals. Methy l ether derivatives of cyclitols may have roles as cryoprotectants, de siccation protectants, and hydroxyl radial scavengers.