Chemistry of fruit wall and seed in Cyperaceae tribe Trilepideae

•First time analyses of silicon in fruit wall in Cyperaceae tribe Trilepideae•First time analyses of element composition in phytin globules in Cyperaceae•Measurements of fruit wall cell structure in Trilepideae

Transverse sections of the fruit walls and seeds from all four genera of family Cyperaceae tribe Trilepideae were investigated using SEM and energy dispersive x-ray analysis (EDXA) to determine the presence of different elements in different parts of the fruit wall and in phytin globules of the aleurone layer of the seed. This is a novel systematic method as previous investigations of elements in the fruit wall have focused almost exclusively on the morphology of silica phytoliths and not the actual occurrence of Si and other elements in the various parts of the fruit wall. In Cyperaceae seed presence of phytin globules rich in P, Mg and K in Cyperaceae seeds are here described and illustrated for the first time. Silicium-rich papillae were present in all epidermis cells of the pericarp in all genera in tribe Trilepideae, being an additional indication that the fruit-cover in this tribe is not an utricle but rather a pericarp. Although tribe Trilepideae is an early diverging clade within subfamily Cyperoideae, it has a pericarp typical of most of the subfamily, including the large genera Carex and Cyperus in the more derived clades.