027 Chapter 27

41. Positive phototropism is due to . A. elongation of cells on the shady plant side. B. a pigment similar to riboflavin acts as a light photoreceptor. C. auxin migrates from the bright side of the plant to the shaded plant side. D. All of these cause positive phototropism. 42. Gravitropism in roots . A. is positive when plant roots grow downward. ................
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