Download Botany 205- Mini Exercise #2

September 26th 2010
Botany 205- Mini Exercise #2:
Modified Leaf Structures and Functions
Lithops (Stone plants)
There are only two leaves. They are
swollen and contain water. The scarcity
of water demands that young plants
limited to only two leaves and a root
system, as more extravagant growth
would only serve to waste water. Almost
the entire plant is devoted to the
function of water storage.
http://www.lithops.info/
Mimosa pudica (Sensitive plant)
The leaves fold up when touched. If
touched with a bit more force, the petioles
will also bend at their pulvinis and the
leaves droop. These movements are called
seismonastic movements (reaction to
physical shock). At night, the leaves will
also fold and bend in movements known
as nyctonastic movements (reaction to
absence of light).
The movement occurs when specific
regions of cells lose turgor pressure, which
is the force that is applied onto the cell
wall by water within the cell vacuoles and
other cell contents.
http://www.plantoftheweek.org/week14
7.shtml
http://en.wikipedia.org/wiki/Mimosa_pu
dica
Botany 205
Ashley Erin Solomon
September 26th 2010
Sarracenia purpurea- Pitcher Plant
Although its large leaves resemble tall pitchers partially filled with water, they are
also good mimics of flowers, and it is the latter trait that fools both insects and
humans. As the summer season progresses, the leaves become purplish red from the
presence of anthocyanins, making them a lure to flies who are probably also
attracted by the decaying amino acid odor of already trapped prey. Once the fly
enters the hollow leaf, it confronts a waxy surface leading to a pool of water.
Although a fly can often escape the surface of water, the pitcher plant reduces its
chances by supplying a wetting agent that wets the fly's wings and prevents it from
flying. Even if the fly succeeds in escaping the surface of the water, it is confronted
by the steep sides of the leaf and, being unable to fly straight up like a helicopter, is
forced to crash into the walls of the leaf. The lower part is waxy and very slippery.
The fly's feet soon slide like stepping onto a newly waxed floor in your sock feet. But
if the fly does succeed in passing above that waxy zone, it is confronted with
downward pointing hairs, again preventing escape. Eventually the exhausted fly
succumbs to the solution at the bottom of the leaf and the low pH slowly digests its
tissues. Cool !!
Botany 205
Ashley Erin Solomon