Listen to part of a lecture in a biology class. Professor: Today we're going to talk about a fascinating adaptation in desert plants. One remarkable example is the saguaro cactus, found in the Sonoran Desert. The saguaro can grow to be over 20 meters tall, but what's truly amazing is how it survives long periods without rain. Its root system is shallow and widespread, extending up to 15 meters from the base, allowing it to quickly absorb water from even light rainfall. However, the key to its survival is its accordion-like pleats. When water is available, the cactus absorbs it and expands, storing water in its thick, fleshy stems. During drought, it uses this stored water and slowly contracts. Additionally, the saguaro has a waxy coating that reduces water loss, and its spines provide shade and reduce airflow near the surface. Interestingly, studies show that a saguaro can store up to 200 gallons of water during a single storm, enough to last for months. So, despite extreme heat, this cactus thrives by maximizing water uptake and minimizing loss.
❓ 题目 What is the main purpose of the saguaro cactus's accordion-like pleats?
A. A. To help the cactus absorb sunlight more efficiently
B. B. To allow the cactus to expand and contract with water storage
C. C. To deter animals from eating the cactus
D. D. To increase the cactus's height for better seed dispersal
✅ 正确答案
B. To allow the cactus to expand and contract with water storage
