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- Test your knowledge of the five major classes of plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene) by matching one hormone to each lettered box. (Note that some hormones will match up to more than one box.)
Problem 1
Problem 2
During winter or periods of drought, which one of the following plant hormones inhibits growth and seed germination?
a. Ethylene
b. Abscisic acid
c. Gibberellin
d. Auxin
Problem 3
Auxin causes a shoot to bend toward the light by
a. Causing cells to shrink on the dark side of the shoot
b. Stimulating growth on the dark side of the shoot
c. Causing cells to shrink on the lighted side of the shoot
d. Stimulating growth on the lighted side of the shoot
Problem 4
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
Problem 5
Plant hormones act by affecting the activities of:
a. Genes
b. Membranes
c. Enzymes
d. Genes, membranes, and enzymes
Problem 6
Buds and sprouts often form on tree stumps. Which hormone would stimulate their formation?
a. Auxin
b. Cytokinin
c. Abscisic acid
d. Ethylene
Problem 7
Which of the following is a type of defense used by plants to deter herbivores?
a. Chemicals toxic to the herbivore
b. Chemicals that recruit other animals
c. Spines
d. a, b, and c
Problem 8
"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"
- A certain short-day plant flowers only when days are less than 12 hours long. Which of the following would cause it to flower? a. a 9-hour night and 15-hour day with 1 minute of darkness after 7 hours b. an 8-hour day and 16-hour night with a flash of white light after 8 hours c. a 13-hour night and 11-hour day with 1 minute of darkness after 6 hours d. a 12-hour day and 12-hour night with a flash of red light after 6 hours
Problem 15
Problem 16
If apples are to be stored for long periods, it is best to keep them in a place with good air circulation. Explain why.
- Write a short paragraph explaining why a houseplant becomes bushier if you pinch off its terminal buds.
Problem 17
- A plant nursery manager tells the new night security guard to stay out of a room where chrysanthemums (which are short-day plants) are about to flower. Around midnight, the guard accidentally opens the door to the chrysanthemum room and turns on the lights for a moment. How might this affect the chrysanthemums? How could the guard correct the mistake?
Problem 18
Problem 19
A plant biologist observed a peculiar pattern when a tropical shrub was attacked by caterpillars. After a caterpillar ate a leaf, it would skip over nearby leaves and attack a leaf some distance away. Simply removing a leaf did not trigger the same change nearby. The biologist suspected that a damaged leaf sent out a chemical that signaled other leaves. How could this hypothesis be tested?
- Imagine the following scenario: A plant biologist has developed a synthetic chemical that mimics the effects of a plant hormone. The chemical can be sprayed on apples before harvest to prevent flaking of the natural wax that is formed on the skin. This makes the apples shinier and gives them a deeper red color. What kinds of questions do you think should be answered before farmers start using this chemical on apples? How might the scientist go about finding answers to these questions?
Problem 20
Problem 21
The discovery of auxin is a good example of how scientists build upon each other's work. For each of the three sets of researchers discussed in the chapter (the Darwins, Boyle-Jensen, and Went), write a one-sentence summary of what they discovered. If you were going to credit one person as being the 'discoverer' of auxin, who would it be?