TISSUE-SPECIFIC SOLUBLE SUGARS IN SEEDS AS INDICATORS OF STORAGE CATEGORY

The accumulation of specific soluble carbohydrates has been implicated in the acquisition of desiccation tolerance and improved longevity in orthodox seeds, leading to the hypothesis that carbohydrate compositi on might be used as a diagnostic marker for seed storage category. We have studied the sugar composition of 46 tissues from seeds of 18 spec ies, covering 13 genera and ten families, and representing three seed storage categories: orthodox, intermediate and recalcitrant. Soluble c arbohydrate extracts from each tissue were analysed using High pH Anio n Exchange Chromatography. Total sugar content and sucrose level of th e embryo were highly variable across all species and no simple associa tion with seed storage physiology was evident. Monosaccharide levels w ere found to be low in most seeds studied, including those of the reca lcitrant category. Sucrosyl-oligosaccharides, raffinose and stachyose, were observed to be lower in recalcitrant seeds compared to orthodox seeds. In general, orthodox and recalcitrant seeds had tissues with su crosyl-oligosaccharide:sucrose mass ratios of > 0.143 (i.e. 1:7) and < 0.083 (1:12) respectively. Moreover, large variations in the content of these sugars were noted between different tissues within the recalc itrant and intermediate seeds. The results from the present study in c ombination with data in the literature show that the ratio of sucrosyl -oligosaccharide:sucrose in seed tissues is generally a good indicator of seed storage category. (C) 1996 Annals of Botany Company.