Cactus lose very little water through transpiration. The leaves in cactus plants are present in the shape of spines. This helps in reducing loss of water from the leaves through transpiration. It's stem is covered into leaf- like structure.Photosynthesis is these plants usually carried out by the stems.The stem is also covered with a thick waxy layer, which helps to retain water. Cactus plants have roots that go very deep into the soil for absorbing water.

Adaptations of Cactus to Survive in a Desert

Cacti are remarkable plants that have evolved a range of adaptations to survive in harsh desert environments. These adaptations allow them to thrive in arid conditions where other plants struggle to survive. Here are some key ways in which cacti are adapted to their desert habitat:

1. Water Storage

Cacti have the ability to store water in their thick, fleshy stems, leaves, or roots. This adaptation enables them to survive long periods of drought. The waxy outer layer of their stems and leaves, called the cuticle, helps to prevent water loss through evaporation. Some cacti also have a shallow but extensive root system that allows them to quickly absorb any available water.

2. Reduced Leaf Surface Area

To minimize water loss through transpiration, cacti have evolved reduced leaf surface area. Instead of large, broad leaves that would lose water rapidly, cacti have spines that serve multiple purposes. The spines help to shade the plant, reducing sunlight exposure and thus minimizing water loss. Additionally, the spines create a layer of still air that reduces the rate of transpiration.

3. CAM Photosynthesis

Cacti have a unique form of photosynthesis called Crassulacean acid metabolism (CAM). Unlike most plants, which open their stomata during the day and close them at night, cacti open their stomata at night to reduce water loss through evaporation. They then fix carbon dioxide into organic acids, which are stored in vacuoles until daylight when the stomata close. This enables cacti to carry out photosynthesis while minimizing water loss.

4. Efficient Water Absorption

Cacti have evolved specialized structures called areoles, which are small raised areas on the stems where spines, branches, and flowers emerge. Areoles also contain clusters of spines and woolly hairs, which help to shade the plant and reduce water loss. These structures also absorb moisture from the air and channel it towards the roots, allowing cacti to efficiently capture any available water.

5. Protection from Predators

The spines of cacti not only serve to reduce water loss but also act as a defense mechanism against herbivores. The sharp spines deter animals from grazing on the cacti, protecting them from being eaten. Some cacti even have spines that detach easily and become embedded in an animal's skin, causing irritation and discouraging further predation.

In conclusion, cacti have evolved a range of adaptations to survive in desert environments. These adaptations include water storage, reduced leaf surface area, CAM photosynthesis, efficient water absorption, and protection from predators. These remarkable adaptations allow cacti to thrive in arid conditions where other plants struggle to survive.