Page 125 - Photosynthesis: The Green Miracle

Harun Yahya

Turgor Movements Mitochondria
Turgor pressure arises with Cell wall
Vacuole
the pressure on the cell walls H O Cytosole
2
from the water that collects in-
side. This water pressure acts
to make the cells rigid and per-
mits the plant to hold itself up- Turgor
right. That is why plants that (pressure) Vacuole
membrane
are not watered wither and
droop. Some plant movements Chloroplast
that take place in response to a
specific stimulus are the result of a

loss of this turgid pressure in the leaf. Turgor in a plant cell
The sensitive plants fade very
quickly. When touched, their leaves suddenly wither. The moment a leaf
is stroked, the stimulus travels around the whole plant until all the leaves
do so. Both electrical and chemical processes are involved in this mecha-
nism. Under the leaves, there are supporting extensions rather resembling
cushions known as the pulvinus. When a leaf receives stimulus from a

touch, heat or wind, a chain reaction begins in which potassium ions trav-
el from one pulvinus to the next. This is followed by a very fast contrac-
tion movement initiated by the water molecules in the parenchyma cells in
one half of the pulvinus traveling towards the other. This movement leads
to a loss of water pressure, and thus to the bending of the entire leaf. The
whole process takes place in a matter of seconds. 59
This pressure variation is used in the system employed in the closing
60
of the traps of some carnivorous plants. Intercellular pressure serves just
as important a function in plants as muscles do in the human body. Water

raised by special channels in the tree stem, using an astonishing mecha-
nism, up to the leaves at the very tops of trees many meters high fills cav-

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