OLD WHORLS FOR STORAGE. “Carbon metabolism seems to be affected by long-term factors that increase levels of the main carbon metabolites as whorls age. This may be because young whorls have high metabolic rates and hence highly dynamic carbohydrate catabolism while, in contrast, old whorls may assimilate surplus carbon and play a role as metabolite stores. This is consistent with two of the strongest correlations detected, between the expression of a gene encoding a hexose transporter and the relative abundances of sucrose and pinitol.”
http://jxb.oxfordjournals.org/content/66/11/3113.full