An outer layer of empty cells in the aerial roots of epiphytic orchids and aroids.
- ‘The role of the velamen is to absorb moisture from the ambient atmosphere, and, may be, to protect from cold or heat.’
- ‘While dry, the velamen may provide a barrier to water loss via transpiration from the wet, internal cells of the root.’
- ‘Over watering turns the velamen brown and mushy and the roots lose their ability to absorb water.’
- ‘When water is in short supply, the dry velamen restricts water loss from the roots.’
- ‘Orchid roots are covered with a special tissue called velamen occurring only in a very few non-orchid plant families.’
Late 19th century: from Latin, from velare ‘to cover’.
We take a look at several popular, though confusing, punctuation marks.