For the genus of ctenophores, see Velamen (ctenophore).
Velamen or velamen radicum is a spongy, multiple epidermis that covers the roots of some epiphytic or semi-epiphytic plants, such as orchid and Clivia species.
The velamen of an orchid is the white or gray covering of aerial roots (when dry, and usually more green when wet as a result of the appearance of underlying photosynthetic structures). It is many cell layers thick and capable of absorbing atmospheric moisture and nutrients, but its main function may lie in protecting the underlying cells against damaging UV rays (Chomicki et al., 2015).
Often, the roots of orchids are associated with symbiotic fungi or bacteria; the latter may fix nutrients from the air. This functionality allows the orchid to exist in locations that provide a reproductive or vegetative advantage such as improved exposure or reduced competition from other plant species.
The velamen also serves a mechanical function, protecting the vascular tissues in the root cortex, shielding the root from transpirational water loss, and, in many cases, adhering the plant to the substrate.
The typical orchid root has a stele of comparatively small diameter. It is surrounded by a cortex which is further enveloped by a highly specialized exodermis, most of which at maturity do not contain protoplasm. A few cells, however, are living and allow the passage of water through them. The exodermis is surrounded by velamen, consisting of one to several layers of cells, which can develop root hair under proper environmental conditions.
The velamen arises from the root tip by division of a special tissue. The dead cells of velamen diffuse light, thus giving it a grey appearance—except at the tips, where the chlorophyll become visible. Upon absorbing water, the dead cells become transparent, and the whole velamen tissue then appears green.
Velamen or velamen radicum is a spongy, multiple epidermis that covers the roots of some epiphytic or semi-epiphytic plants, such as orchid and Clivia...
Velamen is a genus of ctenophores belonging to the family Cestidae. It contains a single species, Velamen parallelum. The species is less than 20 cm long...
In the older parts of the roots, a modified spongy epidermis, called a velamen, has the function of absorbing humidity. It is made of dead cells and can...
surprising results in studies on aerial roots of orchids show that the velamen (the white spongy envelope of the aerial roots), are actually totally waterproof...
which contains two genera: Cestum and Velamen. Each genus contains one species. Cestum veneris Lesueur, 1813 Velamen parallelum (Fol, 1869) Wikispecies has...
plants. veinlet A small vein; the ultimate (visible) division of a vein. velamen A spongy tissue covering the aerial roots of orchids and some other epiphytes...
all the plant's photosynthesis. Their outer layer is an example of the velamen typical of most epiphytic orchids. Its functions include the absorption...
submerged leaves (water plantain, flowering rush). Specialized root types Velamen – epidermis of subaerial roots in some orchids and other epiphytic plants...
to 1.5 meters (4.9 ft) long, and can undulate slowly or quite rapidly. Velamen parallelum, which is typically less than 20 centimeters (0.66 ft) long...
base of the stem. The root is composed of a spongy outer layer called the velamen, which is responsible for protecting underlying cells from UV rays and...
Baissac, Yves; Jay‐Allemand, Christian; Renner, Susanne S. (2015). "The velamen protects photosynthetic orchid roots against UV‐B damage, and a large dated...
rhizome. This rhizome is clothed in a somewhat transparent, silvery-gray velamen. The flowers grow solitary on short stalks, called scapes, from the base...
leaves. The roots are the main photosynthetic organs of the plant. The velamen of the roots has 2-3 separate layers. Wikimedia Commons has media related...
"ROOTS OF SOBRALIA MACRANTHA (ORCHIDACEAE): STRUCTURE AND FUNCTION OF THE VELAMEN‐EXODERMIS COMPLEX". American Journal of Botany. 69 (4): 608–614. doi:10...
Ecclesiastical Literature. Harper & Bros. p. 739. A white veil or coif, called velamen dominicale, was worn by females at the time of receiving the eucharist...
plants also contain Chelidonic acid, saponins, while some species contain Velamen. The epicuticular wax is of the Convallaria type, consisting of parallel...
specimen.k000322364 Zotz, G., Schickenberg, N., & Albach, D. (2017). "The velamen radicum is common among terrestrial monocotyledons." Annals of Botany,...
with a special, usually 4- to 5-cell layer thick, spongy tissue (called Velamen), which helps the plant to absorb moisture from the atmosphere. Epiphytic...
Christian faith. Oremus et pro Iudæis: ut Deus et Dominus noster auferat velamen de cordibus eorum; ut et ipsi agnoscant Iesum Christum Dominum nostrum...
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