Compared with Young Trees Growing Out in the Open, Young

Multiple Choice

Compared with young trees growing out in the open, young trees growing in a darker forest understory tend to have longer, thinner trunks with less branching.This developmental pattern is principally caused by

A) phototropism.
B) thigmotropism.
C) activated phytochrome being converted to inactive phytochrome.
D) inactive phytochrome being converted to active phytochrome.
E) none of these.