1. When a horizontally positioned plant responds to gravity, (1 point)
auxins in the lower sides of stems cause cell elongation that bends the stem upright.
the shoot bends to grow downward, toward the force of gravity.
all parts of the plant bend upward, away from the force of gravity.
auxins in the shoot cause the growth of tendrils to pull the shoot upwards.
2. The growth of ivy tendrils that wrap around objects is an example of (1 point)
gravitropism.
phototropism.
thigmotropism.
photoperiodism.
3. The growth of plant seedlings is usually (1 point)
phototropic and gravitropic.
thigmotropic and gravitropic.
phototropic and influenced by ethylene.
gravitropic and influenced by ethylene.
4. The brilliant colors of leaves in the fall are the result of (1 point)
new synthesis of orange and yellow pigments in leaves.
the movement of chlorophyll from the stems to the leaves.
the production of anthocyanin and the breakdown of chlorophyll.
the decrease of auxins in the meristems and the increase of phytochrome in the leaves.
5. A commercial flower grower could induce winter flowering of a long-day plant by (1 point)
fertilizing the plant with nitrogen.
treating the plant with gibberellin.
covering the plant with an opaque cloth in the late afternoon.
exposing the plant to a brief period of light in the middle of the night.