MadSci Network: Botany |
Hello Katie, neat question. Let's break it down into sections:
PLANT NERVES
Plants don't actually have nerves. What you're seeing is called
seismonasty (or thigmonasty). Seismonastic movements are the result of a plant's ability
to transmit a stimulus from touch-sensitive cells in one part of the plant
to responding cells located elsewhere. The Venus-flytrap uses seismonastic
movement to gather nutrients for itself.
PLANT NUTRIENTS AND NUTRIENT-GATHERING MECHANISMS
As most plants are unable to move around to forage for food, they rely on
their leaves to produce simple sugars through photosynthesis, and on their
roots to absorb mineral nutrients from the soil. Nutrient availability
happens to be dependent on the soil pH, and in areas such as acid or peaty
bogs, there aren't very many nutrients at all.
This is where you would find insect-catching plants such as the Venus-flytrap,
the sundew and the pitcher plant. These plants have modified their leaves
from photosynthetic to insect-catching functions.
THE
VENUS-FLYTRAP
In the case of the Venus-flytrap, the end of a leaf consists of two lobes
joined along the central axis.
Each lobe contains tiny trigger hairs
attached to "motor" cells in the epidermal (outermost) layer of the leaves.
When two or more hairs (or if one hair is touched twice) in succession, then
the motor cells are stimulated to move positive ions from within the cell
to the cell wall. This occurs all along the outer surface of the central
portion of the lobes of the trap. This change in pH expands the outer
epidermal cells along the central portion of the leaf, and since the inner
epidermal cells have not changed in size, the flytrap snaps shut. **This
takes about 1-2 seconds and a LOT of energy to accomplish.** Once shut,
glands touching the insect secrete digestive enzymes- and thus the prey is
dissolved and absorbed by the plant. When empty, epidermal cells along the
midrib of the inner surface of the leaf expand and the leaf opens once
more. This less strenuous activity takes about 8-12hrs to accomplish.
Hope this answers your question!
Evelyn E. Tsang Biology Graduate Student McGill University
Try the links in the MadSci Library for more information on Botany.