Buds and sprouts often form on tree stumps. Which hormone would stimulate their formation?
a. Auxin
b. Cytokinin
c. Abscisic acid
d. Ethylene

In autumn, the amount of _________ increases and the amount of _________ decreases in fruits and leaf stalks, causing a plant to drop fruit and leaves.

a. Ethylene … auxin

b. Gibberellin … abscisic acid

c. Cytokinin … abscisic acid

d. Auxin … ethylene

What evidence suggests that ABA from roots can signal guard cells to close?

a. If roots are given sufficient water, guard cells close anyway.

b. If roots are dry, guard cells begin to close—even though leaves may not be experiencing water stress.

c. Applying ABA to guard cells directly causes them to close.

d. If roots are dry, the ABA concentration in leaf cells drops dramatically.

Plant hormones act by affecting the activities of:

a. Genes

b. Membranes

c. Enzymes

d. Genes, membranes, and enzymes

Why was it logical to predict that amyloplasts function as statoliths?

a. They are dense and settle to the bottom of gravity-sensing cells.

b. They are present only in gravity-sensing cells.

c. They make a direct physical connection with membrane proteins that have been shown to be gravity-receptor molecules.

d. Their density changes in response to gravity.

A plant mutant that shows normal gravitropic bending but does not store starch in its plastids would require a reevaluation of the role of

a. Statoliths

b. Auxin

c. Calcium

d. Differential growth

To explore how hormones function, researchers have begun to transform plants with particular genes. In one experiment, a gene involved in cytokinin synthesis was introduced into tobacco plants. Which one of the following results would be expected?

a. Individuals produced more lateral branches.

b. Stems grew extremely tall and slender.

c. Roots were incapable of responding to gravity.

d. Stomata were closed most of the time.

"Match each definition with the correct term.

Bending of a shoot toward light, Growth response to touch, Cycle with a period of about 24 hours Pigment that helps control flowering Relative lengths of night and day Growth response to gravity Folding of plant leaves at night

a. Phytochrome

b. Photoperiod

c. Sleep movement

d. Circadian rhythm

e. Thigmotropism

f. Phototropism

g. Gravitropism"

Indicate the response to each condition by drawing a straight seedling or one with the triple response.