AP BIOLOGY

Detailed explanation-1: -Cacti have a thick, hard-walled, succulent stem to store water, when it rains. Generally, the stem is either spongy or hollow towards the inside. The water loss from the stem is null due to a thick, waxy coating. It keeps the water inside the cactus thus preventing evaporation.

Detailed explanation-2: -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.

Detailed explanation-3: -In xerophytic plants (cactus), the epidermal layer secretes a thick and waxy layer called the cuticle. This layer closes the stomata and prevents water loss by the transpiration process (water-resistant layer). As the cactus plant lives in a water-deficit area such thick and waxy cuticle is seen.

Detailed explanation-4: -Succulents have dense, broad leaves that store water, and often have a waxy coating that helps prevent evaporation. Many succulents, such as the aloe vera, can store up to 96 liters (25 gallons) of water in their leaves.

Detailed explanation-5: -The big and tall plants are trees, which possess very thick, hard, and woody stems known as the trunk. This trunk or the single main stem gives rise to several branches, which bear flowers, leaves, and fruits.