Question

The plants growing in a desert to tolerate water stress have
A.Few or no leaves
B.Long roots reaching water table
C.Stem modified in to leaf-like form
D.All the above

Answer 1

Hint: The plant organs which help in water intake are roots. The water is lost from plants through leaves and to store water plants need a thicker stem.

Complete step by step answer:
-The plants which grow in extreme dry conditions (desert) are called xerophytes.
-The plants which have undergone modifications to thrive through these extreme dry conditions are called xenomorphs.
-The xerophytic adaptations of the plants help it the better in harsh conditions.
-The adaptations mainly occur in the stem, leaves and the roots.
-The leaves which are green normally helps in photosynthesis for the production of food. -Transpiration occurs through leaves which will spend water.
-In xerophytic conditions, where the water availability is scanty, excess transpiration will cause a disadvantage. Thus the leaves are few in number or reduced or even absent.
-The water is rarely or not available in the soil surrounding the plants due to scanty rainfall. So, to get water the roots need to be long enough to reach the water table.
-Since, the leaves are either absent or reduced, the function of food production by the leaf has to be carried out by the stem. Thus the stems are green, to take part in photosynthesis, flattened and fleshy to store water in it.

Hence, the correct option is ‘D’.

Additional information:
Leaves can be modified into spines. The stem which is modified into green flattened structures is called phylloclade. The xerophytes mostly contain sunken stomata to reduce transpiration. These are few other adaptations of xerophytic plants. Example: Aloe, Euphorbia tirucalli, Muhlenbeckia.

Note:
Xerophytic plant adaptation occurs in roots, stem and leaves of a plant. The adaptations mainly indicate methods to get water and to store the absorbed water.