Question

List five adaptations found in desert plants to reduce transpiration.

Answer 1

Desert plants live in an environment of water scarcity. Therefore, desert plants have adapted the following adaptations to reduce the water loss by transpiration:

1. Leaves convert into spines:

1. These are found in the cactus, e.g. Opuntia in which the stem gets converted into green thick leaf-like structures called phylloclade and starts performing photosynthesis, while leaves get converted into spines.
2. The surface area of spines is smaller than leaves. As a result, the effective surface area for transpiration gets reduced, so, the rate of transpiration reduces.

2. Leaves roll up:

1. The leaves of certain xerophytic plants roll up on bright sunny days.
2. The rolled-up leaves hide the stomata inside the curled surface blocking the direct contact of stomata with the outer dry air and bright sun.
3. Overall reduces the rate of transpiration.

3. Sunken stomata:

1. Stomata in certain xerophytic plants like Nerium get sink into the epidermis. They are then surrounded by air pockets with still and humid air trapped inside. These also get covered with fine air like structures inside the air pocket.
2. This sunken stomata apparatus blocks the direct contact of stomata to an outer dry environment.
3. This reduces the rate of transpiration.

4. Stomata only on lower surface of leaves:

1. There are certain leaves in which the stomata are found only on the lower surface leaves. These are called Hypostomatous leaves.
2. The lower surface of the leaves is not in direct contact with the bright sun, so, compared to the upper surface of the leaf the rate of transpiration at the lower surface of the leaves is lesser.

5. CAM pathway:

• CAM stands for Crassulacean Acid Metabolism. It is a modification of photosynthetic in plants for lower and periodic availability of water.
• CAM plants keep their stomata closed during the day and open them at night only.
• They collect CO₂ at night and form organic acids.
• These organic acids collected inside the photosynthetic cells are decarboxylated during the day to release CO₂, which is then fixed by following the Calvin cycle.
• In this way, CAM plants do not open their stomata during the day and still, the photosynthesis continues.
• Since stomata do not open up in intense heat during the day, the rate of transpiration gets reduced.