Helical cell wall thickenings in Aspleniaceae
Extraxylary helical cell wall thickenings (HCWTs) in vascular plants are not well documented. Leroux et al. study their occurrence and composition in the root cortex of the fern family Aspleniaceae and show that these walls are non-lignified, but are rich in cellulose, hemicelluloses and pectins. Moreover, the occurrence of HCWTs in Aspleniaceae is taxonomically significant as taxa possessing HCWTs are grouped in one, strongly supported, monophyletic clade. When present, they mechanically stabilize the cortex tissue and allow maximal uptake of water and nutrients during rainfall events.
