Why some plants don’t need water and other need water almost every day

Cacti are a type of succulent plant that is native to the Americas. Unlike most plants, cacti do not have leaves in the traditional sense. Instead, they have modified stems that are adapted to perform the functions of leaves, such as photosynthesis and water storage.

Structure of cacti

There are a few reasons why some plants, such as cacti, can survive with very little water, while others need regular watering. One reason is the physical structure of the plant. Cacti and other succulents have evolved to survive in arid environments, without much access to water. Cacti are native to desert regions, where water is scarce, and have evolved specialised adaptations that allow them to conserve water and survive in these harsh environments. They have thick, fleshy stems and leaves that store water, which allows them to survive for long periods of time without needing to be watered. In contrast, plants that require regular watering often have thin, delicate leaves and stems that cannot store as much water.

The stems of cacti are typically thick and fleshy, and they are covered with spines. These spines are modified leaves that grow from the stem, and they provide protection against herbivores, reduce water loss, and anchor the plant to the ground. In some cases, cacti may also have root spines, which are similar to surface spines but grow from the base of the plant.

Because cacti do not have leaves, they are able to conserve water and survive in dry, arid environments. Their thick, fleshy stems are able to store large amounts of water, and they are able to perform photosynthesis using their stems instead of leaves. This allows cacti to thrive in hot, dry conditions where other plants would struggle to survive.

Spines help cacti to accumulate water

In general, the leaves and stem of cacti are highly adapted to their environment and play a vital role in the plant’s survival. Their modified stems allow them to conserve water and perform photosynthesis, while their spines provide protection and stability. These adaptations have helped cacti to thrive in a variety of habitats and make them a unique and fascinating group of plants.

Cacti also have several other adaptations that help them conserve water. 

• Thick, waxy skin on their leaves and stems, which reduces water loss through evaporation
• Small, reduced leaves that minimise the plant’s surface area and thus reduce water loss
• Shallow but widespread root systems that can tap into underground water sources
• The ability to open and close their pores (stomata) to regulate the amount of water lost through transpiration

Root system

The root system of cacti and other succulents is typically shallow and widespread, allowing the plant to quickly absorb water and nutrients from a larger area during periods of rainfall. This adaptation is necessary because cacti often grow in arid environments where water is scarce. During periods of no rain, cacti rely on their shallow root systems to access any remaining moisture in the soil. As the soil dries out, the cactus’s roots can spread out and search for pockets of water that may still be available. This helps the plant to survive during extended periods of drought.

In addition to their shallow root systems, some cacti also have the ability to store large amounts of water in their stems. This allows the plant to survive for long periods without rainfall and can help it to withstand extended periods of drought. The saguaro cactus, for example, can store up to 200 litres of water in its stem. This is enough to last for several months.

The shallow root system also helps the plant to anchor itself to the ground and prevent it from being blown over by strong winds. In some cases, cacti may develop a taproot, which is a single, large root that grows straight down into the ground, but this is not common. In contrast, plants that require regular watering often have deep, dense root systems that are less efficient at absorbing water from a wide area.

The ability of a plant to survive with little water depends on a combination of factors, including its physical structure, root system, and the environment in which it grows. Cacti and other succulents are well-adapted to survive in arid environments. Contrary to other plants that require regular watering and often thrive in environments with more abundant water.