(ii) When do the desert plants take up carbon dioxide and perform photosynthesis ?

Desert plants, also known as CAM (Crassulacean Acid Metabolism) plants, have adapted to their harsh environment by taking up carbon dioxide and performing photosynthesis at night. Here's the step-by-step process:

1. During the night, when the temperature is cooler, the stomata (small openings on the leaves) open. This is the opposite of most plants, which open their stomata during the day.

2. Carbon dioxide enters the plant through these open stomata.

3. The carbon dioxide is stored as a four-carbon acid, hence the name Crassulacean Acid Metabolism.

4. During the day, when the sunlight is available, the stomata close to prevent water loss due to the high temperatures.

5. The stored carbon dioxide is then used to perform photosynthesis while the stomata are closed. The chemical reactions involved in photosynthesis convert carbon dioxide and water into glucose (which provides energy for the plant) and oxygen.

6. The oxygen is released back into the atmosphere through the closed stomata.

This adaptation allows desert plants to conserve water, a precious resource in their arid environments.