Stem Carbohydrate Richness in Two Cycad Species

The pachycaulous stem of cycad plants enables the storage of abundant nonstructural carbohydrates. Cycas revoluta Thunb. and Zamia furfuracea L.f. stems were analyzed for starch and 15 sugars to determine carbohydrate richness. All 15 sugars were detected in both species. The tetrasaccharide stachyose and the disaccharide sucrose comprised most of the sugar content. Total sugar content of these cycad stems was 330 to 360 mg·g−1 and was similar to starch content. The stems of these two species were composed of 64% to 79% nonstructural carbohydrates. The cycad stem is ideally designed to store and mobilize nonstructural carbohydrates to support sink activity when needed, and stachyose may play a prominent functional role.