Leaf modifications in desert

42. Which of the following leaf modifications occur(s) in the desert areas to inhibit water loss?
1. Hard and waxy leaves
2. Tiny leaves
3. Thorns instead of leaves
Select the correct answer using the code given below:
(a) 2 and 3 only
(b) 2 only
(c) 3 only
(d) 1, 2 and 3

Ans-(d) 1, 2 and 3
Exp-“The vegetation of hot desert climate is xerophytic type which has special characteristics to withstand very high rate of evaporation. They have long roots, thick barks, waxy leaves, thorns and little leaves.”

All are correct. These are all desert adaptation of plants.Plants that have evolved mechanisms to combat drought are known as xerophytes. They are perennial shrubs whose root systems below ground are much more extensive than their visible parts or that have evolved tiny leaves with a waxy coating to combat transpiration. And instead of doing away with leaves entirely, the leaves are modified into spines/thorns  that minimise the surface area and so reduce water loss by transpiration. They also protect from animal that might eat them. 

• Desert plants show phenomenon of Allelopathy i,e, they secrete some chemical substance which inhibits the growth of plants growing in their near vicinity .
• Succulent plants store water in fleshy leaves, stems or roots. All cacti are succulents, as are such non-cactus desert dwellers as agave, aloe, elephant trees, and many euphorbias. Several other adaptations are essential for the water storing habit to be effective.
• Owl’s clover, California poppy and other drought avoidance plants die after channeling all their energy into producing seeds
• A succulent must be able to absorb large quantities of water in short periods. Desert rains are often light and brief, and the soil dries rapidly under an intense sun. To cope with these conditions, nearly all succulents have extensive, shallow root systems. The roots of a saguaro extend horizontally about as far as the plant is tall but are rarely more than four inches (10 cm) deep. The water-absorbing roots are mostly within the upper half inch (1.3 cm). So that they can get water from atmosphere.