Biology Essay 06/03/16
Xerophytes
A xerophyte is a certain type of plant that is specially adapted to live in an extreme
environment that has minimal water availability and usually high temperatures such as in a
desert. It is known by biologists that certain environmental conditions affect the way the plant
survives by performing metabolic processes such as photosynthesis, translocation and
especially transpiration in this aspect. Being a xerophytic plant means they have adapted
certain ways to conserve water in such conditions, this morphological change is known as
xeromorphic.
Plants perform a process called transpiration which is essentially the
evaporation of water from the surface of the plant (usually the leaves).
The evaporation creates tension which pulls more water into the leaf;
the water molecules are cohesive so when some are pulled up to the
leaf others follow like a chain. This means the whole column of water in
the xylem moves upwards and water is continuously taken up through
the roots. This idea of the transpiration stream is called the
cohesion-tension theory of water transport in the xylem. The rate of
transpiration is dependent on the water (vapour) potential gradient,
amount of stomata, surface area of leaf (diffusion surface), light
intensity (photosynthesis), temperature, humidity and wind/air
movement.
If the water vapour potential is higher outside the leaf than it will diffuse out down the
diffusion gradient through the stomata, the more negative the atmospheric air is the faster
the rate of transpiration therefore the plant uses more water and thus wilts faster. Xerophytic
plants are able to reduce water loss from the inevitable, natural process. It is vital to maintain
the amount of water. If these plants do not have enough water their cells lose turgor which is
known as plasmolysis, this would be more common and problematic in the dry conditions.
Conservation of water is done primarily through adaptations....