Final answer:
Plants in arid climates typically develop deep roots to access moisture from deep soil layers. Shallow fibrous roots are less effective in such environments as they can't reach deeper water sources. The saguaro cactus is an example of a plant that has adapted with deep roots along with other features to conserve water.
Step-by-step explanation:
Plants have adapted to the arid climate by growing deep roots that tap water from deep underground. This adaptation allows them to access moisture from deeper soil layers that remain moist longer after rainfall. In contrast, a shallow fibrous root system is not as effective in arid climates, as it cannot reach these deeper water reserves and relies on infrequent and light rainfalls that quickly dry up in the desert environment.
For example, some desert plants have taproots that extend up to 20-30 feet underground to access these deeper water sources. A notable example is the saguaro cactus, which not only has a deep root system but also lacks leaves to prevent water loss through transpiration and has a stem capable of storing significant amounts of water.