Describe how xerophytic plants are structurally adapted to their habitat. (20 marks)

Describe how xerophytic plants are structurally adapted to their habitat.


Adaptation of xerophytes
    These are plants which are adapted to withstand harsh environmental conditions like – low supply of water, high day temperatures, windy conditions and low humidity; all these conditions lead into excessive water loss by transpiration; they are therefore adapted by;

    Structural adaptations:-

Their leaves are modified into spines/thorn like structures to reduce surface area exposed for transpiration;

Their stomata are sunken; and water vapour accumulate on the sunken depression; lowering water vapour concentration gradient; between the atmosphere and the sub-stomatal air spaces; this reduces the rate of transpiration;

Leaves have thick waxy cuticles; to reduce cuticular transpiration;

The number of stomata is reduced to minimal to reduce stomatal transpiration.

Deep roots so as to reach and absorb water found in deeper layers in the soil;

They have parenchyma cells (in the stem and leaves); for storage of water when it is in adequate supply for use during drought, (the cactus whose leaves and stem appear succulent);

Some have hairy leaves; that trap water vapour in between them to lower the diffusion gradient hence reducing water loss;

Most xerophytes have sufficient roots; which grow extensively close to the soils surface; enabling them to absorb maximum amount of water after a short shower;