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

Fresh mature tree seeds of 16 species plus soybean were usedfor the analysis of soluble neutral sugar content, as well asfor the determination of longevity in terms of the time requiredfor the seeds to decrease to 50% of the original germinationunder 5C and 80–91% relative humidity. Oligosaccharideswere sometimes found in species of recalcitrant; although themass ratio of oligosaccharide/total sugar or mole ratio of stachyoseand raffinose/sucrose was less than 0.05 or 0.044, respectively.The time required for seeds to decrease to 50% germination variedfrom a few days to 8.3 months for the seeds of desiccation-sensitivespecies. The low ratio of oligosaccharide to sucrose is, however,most unlikely to be a cause of short life-span in recalcitrantseeds. It is suggested that 0.05 mole of oligosaccharide needs to beassociated with one mole sucrose to confer the seeds with desiccationtolerance. Orthodox seeds which have a high ratio of oligosaccharide/totalsugars happened to have a low ratio of disaccharide/total sugarindicating active biosynthetic activity of oligosaccharide.There was a positive correlation between the longevity and themass ratio of oligosaccharide/total sugar or oligo-/disaccharidefor those desiccation-tolerant seeds tested. These results supportthe conclusion that the ratio of oligo-/disaccharide plays arole in the desiccation tolerance and, consequently, the longevityof orthodox seeds. Key words: Tree seed, storage behaviour, recalcitrant, soluble carbohydrate, oligosaccharide, seed longevity