Science and nature

Many desert plants survive long dry periods by storing water in their thick stems and leaves. The saguaro cactus, for example, has pleated ribs that allow its stem to swell after a heavy rain and then slowly shrink as the stored water is used. Because rain in the saguaro's habitat is ______, arriving in brief, heavy bursts separated by months of dry weather, this ability to take in large amounts of water quickly is essential to the plant's survival.