The relationship between carbohydrate composition of some tree seeds and their longevity

Abstract

Fresh mature tree seeds of 16 species plus soybean were used for the analysis of soluble neutral sugar content, as well as for the determination of longevity in terms of the time required for the seeds to decrease to 50% of the original germination under 5°C and 80–91% relative humidity. Oligosaccharides were sometimes found in species of recalcitrant; although the mass ratio of oligosaccharide/total sugar or mole ratio of stachyose and raffinose/sucrose was less than 0.05 or 0.044, respectively. The time required for seeds to decrease to 50% germination varied from a few days to 8.3 months for the seeds of desiccation-sensitive species. The low ratio of oligosaccharide to sucrose is, however, most unlikely to be a cause of short life-span in recalcitrant seeds. It is suggested that 0.05 mole of oligosaccharide needs to be associated with one mole sucrose to confer the seeds with desiccation tolerance. Orthodox seeds which have a high ratio of oligosaccharide/total sugars happened to have a low ratio of disaccharide/total sugar indicating active biosynthetic activity of oligosaccharide. There was a positive correlation between the longevity and the mass ratio of oligosaccharide/total sugar or oligo-/disaccharide for those desiccation-tolerant seeds tested. These results support the conclusion that the ratio of oligo-/disaccharide plays a role in the desiccation tolerance and, consequently, the longevity of orthodox seeds.