Why do deeper roots improve drought tolerance?

• A. They access deeper soil moisture.
• B. They increase evapotranspiration.
• C. They reduce soil nutrients.
• D. They increase disease risk.

Answer: (A)

Deeper roots improve drought tolerance because they reach water stored deeper in the soil profile that shallow roots can’t access during dry periods. When roots extend downward, the plant can tap into moisture that persists after surface soils have dried, helping maintain cell hydration, keep stomata functioning, and sustain growth and photosynthesis through a drought. This access to deeper moisture is the main reason drought tolerance improves with longer rooting depth.

The other options don’t fit because they describe processes or effects that don’t explain why deeper roots help in drought. Increased evapotranspiration would mean more water loss, not improved access to water; reducing soil nutrients would stress the plant and isn’t a drought-tolerance mechanism; and increasing disease risk would be a negative consequence, not a drought-avoidance benefit.