Xerophytes:
Xerophytes
are plants that live in arid/dry environments, such as desserts, beaches and
alpine regions . Examples of xerophytes include cacti and succulents. Xerophytes have a shortage of water , so have special
adaptive features to store and/or reduce the loss of water, so that
photosynthesis and respiration can be carried out .
Xerophytes
have a reduced number of stomata , also the stomata are in sunken
'pits' in the lower epidermis, this traps moist air around the
stomata and therefore reduces transpiration. Xerophytes have very
small , rolled leaves which again traps moist air around the stomata
and decreases surface area to volume ratio , therefore decreases the
rate of transpiration . some xerophytes such as cacti have spines
instead of leaves which significantly reduces the amount of
transpiration as there are no stomata . By
having few stomata and small rolled leaves , xerophytes are able to
maintain water balance , as the rate of transpiration has been
decreased .
Xerophytes also have an
extremely thick waxy cuticle and lightly coloured hair on the
epidermis of the leaves, which reduces transpiration by reducing the
gradient of diffusion, as the hair lowers the wind movement
surrounding the stomata, it also reflects some of the heat as it is
white and shiny , so therefore helps to keep the plant cool . By
having a extremely thick waxy cuticle and lightly coloured hairs on
the epidermis , xerophytes are able to maintain water balance , by
reducing transpiration and also keeping the plant cool , to prevent
further transpiration.
Most xerophytes have very deep root systems that penetrate deep into the
soil / sand (vertically), they are able to absorb any water present
which is then transported by the xylem and phloem (vascular bundle)
to the leaves , to be used for photosynthesis and respiration ,
however some xerophytes such as cacti have very shallow roots , which
are able to absorb any water in the top layers or soil/ sand , which
is then used for photosynthesis and respiration .By
having deep root systems , xerophytes are able to maintain water
balance which is optimum for successful photosynthesis and
respiration, as the roots are able to absorb water in the soil / sand
, which can then be used for photosynthesis and respiration.
In droughts
or periods of extreme heat / dryness , xerophytes lose their leaves
and become dormant , to reduce transpiration and because there is a
lack of moisture in the air . Also some xerophytes such as succulents have special adaptive tissues in their
stems , which store water , which can then be used in droughts , or
when there is no moisture in the air or soil . having
specialised adaptive tissue that stores water , allows xerophytes to
maintain water balance at which they can survive in droughts , or
when there is a lack of moisture in the air or soil / sand .
veins stained purple contain water .
veins stained purple contain water .
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