A comparative study of seed reserve accumulation in five Styrax species with potential for biofuel production

Key Message Carbon competition between starch and oil biosynthesis during seed development of Styrax tonkinensis has been reported, but reserve dynamics indicate an absence of significant carbon competition in other Styrax species. Abstract The accumulation of different storage reserves during seed development can be competitive. Carbon competition (i.e., carbon flow into starch instead of oil) has been reported in Styrax tonkinensis (Pierre) Craib ex Hartwich. In this study, developmental patterns in morphology and the accumulation of major biochemical fractions of five other Styrax species ( S. calvescens Perkins, S. dasyantha Perk., S. faberi Perk., S. japonicus Sieb. et Zucc., and S. odoratissimus Champ. ex Benth.) were analyzed over 50 days. In all species, kernel fresh matter and dry matter increased during development, while the percent water content trended downwards to lower than 40% at the last sampling date. The time to maturity varied with species, as did the evolution of oil, fatty acids composition, sugar, starch, and protein. Contents of these major reserve fractions per kernel increased with development and were strongly correlated with each other. Final oil concentration ranged from 489 to 548 mg g −1 , and the proportions of major fatty acids (palmitic, oleic and linoleic acid) were similar across species (11–15%, 39–41% and 43–47%, respectively). In contrast, starch concentrations never exceeded 7–45 mg g −1 , depending on species and developmental stage. Final protein concentration ranged from 165 to 237 mg g −1 . A slowdown in the speed of oil accumulation midway during development may occur in S. faberi but was not present in the other species. None of the five Styrax species examined here presented evidence for significant carbon competition between starch and oil accumulation.