Several scientists, including Charles and Francis Darwin, Frits Went and others, demonstrated that auxins caused stems to bend toward light in a series of elaborate experiments. Went was the researcher who finally determined that bending of the stem toward light was a result of which mechanism?
A. Light caused a reduction in auxin concentration and a reduction in stem elongation on the lighted side of the plant stem, and thus a bending in the direction of the light.
B. A combination of positive phototropism and a negative gravitropism.
C. The stems actually were responding to the agar blocks that had been used in the experiments.
D. Auxin concentration was equal on both sides (lighted and shaded) of the stem; however, the apical meristem responded to the presence of light.
E. The transport of auxin to the shaded side of the plant stem stimulated stem elongation and a bending in the direction of the light.
Answer: E
You might also like to view...
A simple reflex arc is made up of a sensory receptor and
(a) a sensory neuron. (b) a motor neuron. (c) an effector. (d) all of the above.
What is the principal substance that mediates phototropism in stems?
a. auxin b. gibberellin c. abscisic acid d. ethylene e. cytokinin
The second messenger cAMP is synthesized by the enzyme
What will be an ideal response?
What do plants and animals have in common?
a. both are heterotrophic b. both are autotrophic c. both are prokaryotic d. both are eukaryotic