What You Need:
- Many different cacti samples
- Hand lenses
What Do You Do?
- Use your hand lens to thoroughly examine each type of cactus.
- Draw each cactus in your lab book.
- Describe how each cactus might survive in the harsh desert.
- What adaptations does it have to help it?
Cacti have many adaptations that allow them to live in dry areas; these adaptations let the plant collect water efficiently, store it for long periods of time, and conserve it (minimizing water loss from evaporation).
Cacti have a thick, hard-walled, succulent stem – when it rains, water is stored in the stem. The stems are photosynthetic, green, and fleshy. The inside of the stem is either spongy or hollow (depending on the cactus). A thick, waxy coating keeps the water inside the cactus from evaporating.
Many cacti have very long, fibrous roots, which absorb moisture from the soil. Some, like ball cacti, have shorter, more compact roots that absorb dew water that falls off the cactus.
Instead of leaves, most cacti have spines or scales (which are modified leaves). These spines and scales do not lose water through evaporation (unlike regular leaves, which lose a lot of water). The spines protect the cactus from predators (animals that would like to eat the cactus to obtain food and/or water). Areoles are circular clusters of spines on a cactus. Flowers bud at an areole and new stems branch from an areole.