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

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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;

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