Downward Bending of a Seedling Root Can Be Blocked by ____

Question

Downward bending of a seedling root can be blocked by ____.  
A) moving it to a dark room
B) exposing the seedling to continuous light
C) turning the seedling upside down
D) inhibiting cytokinin transport upwards
E) inhibiting auxin transport downwards

Accepted Answer

Downward bending of a seedling root is caused by the accumulation of auxin on the lower side of the root. Inhibiting auxin transport downwards would prevent this accumulation and thus block the downward bending of the root.