|
Probably the best known among all carnivorous
plants because of its swift movement of trap leaves, the Venus flytrap (Dionaea
muscipula) grows in the coastal savannas of North and South Carolina in the
United States. This is the only region in the world where the plants can be seen
in their native habitat. The plants are typically found on a moist surface in
the open pine tree forest, sometimes on a thick mat of sphagnum moss, sometimes
right on the white sand surface, often in company of other carnivorous
plants in the area such as sundews and terrestrial bladderworts.
The plants are federally protected ..????..
The genus name Dionaea is from
Dione, the goddess of
love, in Greek mythology. Venus, in Roman religion, is identified with the
Greek goddess, Aphrodite, whose mother, according to one account, is
Dione.
The genus Dionaea is monotypic; that
is, there is only one species, Dionaea muscipula. The genus belongs to the sundew family
Droseraceae.
Historical Note
In a historical letter dated Jan. 24, 1760,
Arthur Dobbs, then Governor of North Carolina, wrote, " ...But the great wonder
of the vegetable kingdom is a very curious unknown species of sensitive; it is a
dwarf plant; the leaves are like a narrow segment of a sphere, consisting of two
parts, like the cap of a spring purse, the concave part outward, each of which
falls back with indented edges (like an iron spring fox trap); upon anything
touching the leaves, or falling between them, they instantly close like a spring
trap, and confine any insect or anything that falls between them; it bears a
white flower; to this surprising plant I have given the name of Fly Trap
Sensitive."
Description
The Venus flytrap uses a snap trap (sometimes
referred to as steel trap), the most advanced trap mechanism to be found
among carnivorous plants. The plant forms a rosette of leaves emerging from a
short white rhizome (underground stem) with fibrous roots. The leaves, which
can grow up to 10cm, are of two parts: a flat petiole (leaf stem) and a leaf
blade modified into a trap.
The trap portion consists of two semicircular
lobes united along the midrib of the leaf blade. Around the margin of each lobe
grow stiff, spine-like guard hairs (15 to 20 along each margin), which mesh
together when the trap closes to prevent the prey's escape. Along the inner edge
of each lobe just below these marginal spines runs a narrow band of nectar
glands which secrete sugary substance to attract potential
prey. Much of the inner lobe
below is crowded with numerous digestive glands, which often give the trap
surface a bright-red coloration. Each inner lobe
surface has three -- sometimes 4
or more -- fine bristles located in a triangular pattern. These are trigger
hairs, which are sensitive to physical stimulation and, when properly
stimulated, initiate a rapid trap closure.
Prey Capture
When an unwary insect brushes these hairs,
the trap snaps shut, usually in less than half a second. The guard hairs of each
lobe mesh together to prevent the insect's escape, and the prey is hopelessly
confined between the two lobes. The insect's effort to free itself further
irritates the trigger hairs, causing the lobes to close more tightly. This
pressure sometimes crushes a soft-bodied insect. In several
hours, as the lobes are tightly
sealed, the trap becomes filled with digestive fluids secreted from the
glands on the lobe surface, and the captured
prey begins to dissolve. The trap remains
closed during the digestive process which lasts for a week to ten days depending
on the size of the prey. After the nutrients of the insect body are absorbed by
the plant, the trap opens slowly. Inside the now dry trap is the remains of the
hard shell part of the consumed insect. Wind and rain clean the lobes and
the trap is ready again for another meal. A single trap is usually capable of
repeating this process only three times or so during the life of the trap. After
that it becomes insensitive to stimulation and dies, but new trap leaves are
continuously sprouting out from the rosette center during the growing
season of spring through summer.
When a trigger hair is stimulated by a piece of wood, or a finger, the trap also
snaps shut. In this case, however, the trap opens the next day, since the plant
does not find any nutritious object inside the trap.
|
|