試題詳解

34. A plant seedling bends toward sunlight because
(A)there is more auxin on the light side of the stem.
(B)auxin is destroyed more quickly on the dark side of the stem.
(C) auxin is found in greatest abundance on the dark side of the stem.
(D)auxin migrates to the lower part of the stem due to gravity.
(E)gibberellins produced at the stem tip cause phototropism.