BIOL Ch 33
Methylsalicylic acid is a substance made by plants that _______.
were infected by microbes
Some perennial plants, such as rhubarb and rosemary, live in climates where temperatures are very low for extended periods. Which of the following must occur in such plants before their seeds can germinate in the spring?
Abscisic acid (ABA) must be inactivated by prolonged cold exposure.
______ are made in plant meristems. _____ are made in plant roots.
Auxins: Cytokinins
Phototropism, gravitropism, and thigmotropism have which of the following in common?
Cells become longer on the opposite side of the stem from the location of the stimulus that causes the tropism.
What is the purpose of spraying ethylene on fruit that is already ripe but still on the tree?
Ethylene loosens fruit from stems so it can be picked more easily by machines.
Imagine that the normal concentration of auxin in a plant is 40, while the concentration of cytokinins is 30. (Don't worry about units here.) This plant is tall but does not have many branches. Then a substance is sprayed on the plant that changes the concentrations of both hormones: now, auxin has a concentration of 60, while cytokinins have a concentration of 100. What do you predict would occur?
The plant would grow taller and become much bushier.
Which of the following best describes the function of canavanine?
a chemical that helps plants defend against insects
Which of the following is an INCORRECT pairing of a plant hormone and an important function of that hormone?
abscisic acid: shortens seed dormancy
Phototropism and gravitropism are controlled by _______.
auxins
Which plant hormone(s) is(are) implicated in cell elongation, seed germination, and the undesirable effect called "bolting"?
gibberellins
In early studies, which of the following observations in seedlings showed that phototropism is the result of a chemical that diffuses through the plant body?
inserts of mica, but not inserts of gelatin, eliminated phototropism
Auxin causes plant cells to elongate because it ________.
lowers the pH of the cell wall, activating enzymes that weaken connections between cellulose fibers
An example of a plant defense against being eaten is ______. An example of a plant defense against pathogens is ______.
making caffeine: making methylsalicylic acid
One hypothesis about gravitropism is that granules of _______ within cell organelles respond to gravity, causing a redistribution of the hormone ______. Higher concentrations of this hormone in roots _____ cell elongation.
starch: auxin: inhibit
Which of the following exerts the most important influence on flowering in response to photoperiod?
the length of the continuous dark period to which the plant is exposed
2,4-D is a synthetic auxin that kills eudicots, but not monocots. For which of the following purposes is 2,4-D used in agriculture?
to remove dandelions and other eudicot weeds
What might happen to a plant that has a genetic defect resulting in an underproduction of auxin?
It will have stunted growth.
Which of the following is an INCORRECT statement about circadian rhythms in plants?
Plants' biological clocks are governed by environmental stimuli such as temperature fluctuations.
Which of the following was an observation made by Charles Darwin and his son Francis regarding phototropism?
Shoots with transparent caps on their tips grew toward light, whereas shoots with opaque tips grew straight upward.
The sun comes up, the sun goes down. What effect does this have on plant phytochromes?
Sunlight changes the ratio between two forms of a phytochrome.
Which of the following events occurs at the abscission layer?
The leaf stalk separates from its stem.
Little Maya has brought home a plant from school. It lives next to her bed, but has no flowers. Maya's mother always opens her daughter's door to check on her before she goes to bed. After a few days, beautiful blooms start to appear. Which of the following can explain this?
The plant is a long-day plant and the flash of light from the doorway stimulated it to bloom.
