A Botanist Discovers a Plant That Lacks the Ability to Form

question 18

Multiple Choice

A botanist discovers a plant that lacks the ability to form starch grains in root cells, yet the roots still grow downward. This evidence would refute the long-standing hypothesis that ________.

• A) falling amyloplasts trigger gravitropism
• B) starch accumulation triggers the negative phototropic response of roots
• C) starch grains block the acid-growth response in roots
• D) starch is converted to auxin, which causes the downward bending in roots
• E) starch and downward movement are necessary for thigmotropism