Chapter 26 Plant Hormones

Which plant hormone is a gas?

• auxin
• gibberellin
• ethylene
• cytokinin

Which plant hormone drives production of more proton pumps in the plasma membrane?

• ethylene
• auxin
• gibberellin
• cytokinin

What polysaccharide is the primary component of plant cell walls?

• Expansin
• Cellulose
• Glycogen
• Endosperm

Which hormone promotes seed germination?

• abscisic acid
• ethylene
• gibberellin
• auxin

Stored food reserves in a seed

• endosperm
• embryo
• radicle
• seed coat

Response to light in which plant stems bend toward a light source

• gravitropism
• phototropism
• negative gravitropism
• negative phototropism

Charles and Francis Darwin concluded from their experiments on phototropism by grass seedlings that the part of the seedling that detects the direction of light is the

• tip of the coleoptile.

• part of the coleoptile that bends during the response.

• base of the coleoptile.

• cotyledon.

Plants growing in a partially dark environment will grow toward light in a response called phototropism. Which of the following statements is true regarding phototropism?

• It is caused by an electrical signal.

• One chemical involved is ethylene.

• Auxin causes a growth increase on one side of the stem.

• Auxin causes a decrease in growth on the side of the stem exposed to light.

A plant seedling bends toward sunlight because

• auxin migrates to the lower part of the stem due to gravity.

• there is more auxin on the light side of the stem.

• auxin is destroyed more quickly on the dark side of the stem.

• auxin is found in greatest abundance on the dark side of the stem.

The ripening of fruit and the dropping of leaves and fruit are principally controlled by

• auxins.

• cytokinins.

• indole acetic acid

• ethylene.