A gland is an organ that manufactures or discharge chemical
substances to be used in, or eliminated from, the body . A gland may
vary from a single cell to a complex system of tubes that unite and open
onto a surface through a duct.
Glandulicactus wrightii
A drop of nectar secreted by an
areolar gland (nectary.)
Simple glands are common in the plantkingdom. The sweet
nectar of flowers and the
resinous pitch of pine trees are
substances produced by plant glands. Vegetal glands are special, usually
minute and globular, organ,
embedded or projecting from the surface of the plant that
secretes or
excretes a variety of
liquid substances that have various purposes, hence glandular.
Some common examples of plant glands are:
Nectary: Glands that
produces the nectar a sweet sugary
substance.
Trichomes:
Unbranched hair-like outgrowth of the epidermis, often glandular.
Poison gland: A gland, in animals or plants, which secretes
an acrid or venomous matter, that is conveyed along an organ capable
of inflicting a wound.
Pulvinus:
swelling at the base of a petiole
of a leaf or
leaflet, sometimes glandular or
responsive to touch. hence pulvinate
Some species of climbing
plants develop holdfast roots which help to support the vines on
trees, walls, and rocks. By forcing their way into minute pores and
crevices, they hold the plant firmly in place.
Climbing plants, like the poison ivy (Toxicodendron
radicans), Boston ivy (Parthenocissus
tricuspidata), and trumpet creeper (Campsis
radicans), develop holdfast roots which help to
support the vines on trees, walls, and rocks. By forcing their
way into minute pores and crevices, they hold the plant firmly
in place. Usually the Holdfast roots die at the end of the first
season, but in some species they are perennial. In the tropics
some of the large climbing plants have hold-fast roots by which
they attach themselves, and long, cord-like roots that extend
downward through the air and may lengthen and branch for several
years until they strike the soil and become absorbent roots.
Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House,
1994
