Listen to part of a lecture in an environmental science class. Professor: Today we're discussing a fascinating example of ecological adaptation: the saguaro cactus. Found primarily in the Sonoran Desert, this cactus can live over 150 years and grow to be 40 feet tall. What's remarkable is how it has evolved to survive extreme conditions. Its pleated, accordion-like skin allows it to expand and store water during rare rainfalls, sometimes absorbing up to 200 gallons in a single storm. The shallow root system spreads out widely, just a few inches below the surface, to capture moisture quickly. But water conservation is only part of the story. The saguaro's white flowers open at night, when temperatures drop and pollinators like bats are active. These flowers also have a waxy coating to prevent water loss. Interestingly, the cactus provides shelter for many desert animals, such as woodpeckers, which bore holes in its trunk. In return, these birds help disperse seeds. So, the saguaro is not just a survivor; it's a keystone species in its ecosystem.
❓ 题目 According to the professor, what is one reason the saguaro cactus opens its flowers at night?