Why do roots grow downward?
Show answer & explanation
Answer: Gravity guides root growth
Gravity guides root growth ✓ — Correct! Roots exhibit gravitropism (response to gravity). Special cells in root caps contain starch-filled organelles (statoliths) that settle downward due to gravity. This triggers auxin redistribution, causing cells on the upper side to elongate faster, bending the root downward. This ensures roots find water and anchor the plant!
Water pulls roots down — Wrong. While roots do seek water (hydrotropism), downward growth is primarily controlled by gravity response (gravitropism), not water pulling.
Soil pushes roots deeper — Wrong. Soil doesn't push roots—roots actively grow downward following gravity signals detected by statolith cells in root caps.