What rootstock trait enhances drought tolerance in orchard trees?

• A. A deep, extensive root system and efficient water uptake.
• B. A shallow, fibrous root system limited in depth.
• C. High salinity tolerance in leaves.
• D. Very rapid top growth.

Answer: (A)

Deep, extensive rooting that reaches deeper soil moisture and takes up water efficiently is the key trait. When a rootstock has a deep, well-distributed root system, it can access water stored deeper in the profile and extract it more effectively during drought, helping the tree maintain turgor and growth. This makes the tree more resilient to dry spells and reduces stress on the scion. A shallow, surface-only root system dries out quickly and cannot sustain water supply during drought, which makes trees more vulnerable. Traits like high leaf salinity tolerance address salt stress rather than drought tolerance, and very rapid top growth tends to increase water use rather than conserve it, which can worsen drought stress.