58) If a plant is infected with nitrogen-fixing bacteria, what is the most probable effect on the
plant?
A) It gets chlorosis.
B) It dies.
C) It will have a higher concentration of N2 in its roots and shoots.
D) It will likely grow faster than an uninfected plant.
59) You are weeding your garden when you accidentally expose some roots of your pea plants.
You notice swellings (root nodules) on the roots and there is a reddish tinge to the ones you
accidentally damaged. Most likely your pea plants
A) suffer from a mineral deficiency.
B) are benefiting from a mutualistic bacterium.
C) are developing offshoots from the root.
D) contain developing insect pupa.
60) Which of the following statements about nitrogen fixation in root nodules is true?
A) The plant contributes the nitrogenase enzyme.
B) The process is relatively inexpensive in terms of ATP costs.
C) Leghemoglobin helps maintain a low O2 concentration within the nodule.
D) The process tends to deplete nitrogen compounds in the soil.
61) Upregulation of leghemoglobin biosynthesis in a leguminous species would most likely
indicate
A) the plant is suffering from a mineral deficiency.
B) the successful inoculation of nitrogen-fixing bacteria.
C) the plant is suffering from water stress.
D) an increase in the biosynthesis of amino acids.
62) An example of a mutualistic association between a plant and a fungus would be
A) nitrogen fixation.
B) Rhizobium infection.
C) mycorrhizae.
D) parasitic infection.
63) Hyphae form a covering over roots. These hyphae create a large surface area that helps to do
which of the following?
A) aid in absorbing minerals and ions
B) maintain cell shape
C) increase cellular respiration
D) protect the roots from ultraviolet light
64) Which of the following is a primary difference between ectomycorrhizae and
endomycorrhizae?
A) Endomycorrhizae have thicker, shorter hyphae than ectomycorrhizae.
B) Endomycorrhizae, but not ectomycorrhizae, form a dense sheath over the surface of the root.
C) Ectomycorrhizae do not penetrate root cells, whereas endomycorrhizae grow into
invaginations of the root cell membranes.
D) Ectomycorrhizae are found in woody plant species; about 85% of plant families form
ectomycorrhizae.
65) The earliest vascular plants on land had underground stems (rhizomes) but no roots. Water
and mineral nutrients were most likely obtained by
A) absorption by hairs and trichomes.
B) absorption by mycorrhizae.
C) osmosis through the root hairs.
D) diffusion across the cuticle of the rhizome.
66) A rootless, green plant is found growing on the branches and trunks of rain forest trees, but
lacks any apparent adaptation for collecting rainwater. This plant is most likely
A) an epiphyte.
B) a nitrogen-fixing plant.
C) a carnivorous plant.
D) a parasite.
67) What are epiphytes?
A) aerial vines common in tropical regions
B) haustoria used for anchoring to host plants and obtaining xylem sap
C) plants that live in poor soil and digest insects to obtain nitrogen
D) plants that grow on other plants but do not obtain nutrients from their hosts
68) Carnivorous plants have evolved mechanisms that trap and digest small animals. The
products of this digestion are used to supplement the plant’s supply of
A) energy.
B) carbohydrates.
C) minerals.
D) water.
69) Rhizobia, actinomycetes, and cyanobacteria all share the common feature that they can
A) increase water uptake in plants.
B) increase nutrient availability in the soil for plants.
C) kill parasites in the soil.
D) fix atmospheric nitrogen.
70) Why is nitrogen fixation an essential process?
A) Nitrogen fixation can only be done by certain prokaryotes.
B) Fixed nitrogen is often the limiting factor in plant growth.
C) Nitrogen fixation is very expensive in terms of metabolic energy.
D) Nitrogen fixers are sometimes symbiotic with legumes.
71) In what way do nitrogen compounds differ from other minerals needed by plants?
A) Only nitrogen can be lost from the soil.
B) Only nitrogen requires the action of bacteria to be made available to plants.
C) Only nitrogen is held by cation exchange capacity in the soil.
D) Only nitrogen can be absorbed by root hairs.
72) Nitrogen fixation is a process that
A) recycles nitrogen compounds from dead and decaying materials.
B) converts ammonia to ammonium.
C) releases nitrate from the rock substrate.
D) converts nitrogen gas into ammonia.
73) Which of the following would be the most effective strategy to remove toxic heavy metals
from a soil?
A) heavy irrigation to leach out the heavy metals
B) application of fertilizers to compete with heavy metal uptake
C) adding plant species that have the ability to take up and accumulate heavy metals
D) inoculating soil with mycorrhizae to avoid heavy metal uptake
74) Which of the following plant structures shares the most common features and functions with
a fungal hyphae?
A) stomata
B) vascular cambium
C) lenticels
D) root hairs
75) A plant developed a mineral deficiency after being treated with a fungicide. What is the most
probable cause of the deficiency?
A) Mineral receptor proteins in the plant membrane were not functioning.
B) Mycorrhizal fungi were killed.
C) Active transport of minerals was inhibited.
D) Proton pumps reversed the membrane potential.
76) Pine seedlings grown in sterile potting soil grow much slower than seedlings grown in soil
from the area where the seeds were collected. This is most likely because
A) the sterilization process kills the root hairs as they emerge from the seedling.
B) the normal symbiotic fungi are not present in the sterilized soil.
C) water and mineral uptake is faster when mycorrhizae are present.
D) B and C.
77) Some botanists argue that the entire plant should be considered as a single unit rather than a
composite of many individual cells. Which of the following cellular structures best supports this
view?
A) cell wall
B) cell membrane
C) vacuole
D) plasmodesmata
78) Root hairs are most important to a plant because they
A) anchor a plant in the soil.
B) store starches.
C) increase the surface area for absorption.
D) provide a habitat for nitrogen-fixing bacteria.
79) A water molecule could move all the way through a plant from soil to root to leaf to air and
pass through a living cell only once. This living cell would be a part of which structure?
A) the Casparian strip
B) a guard cell
C) the root epidermis
D) the endodermis
80) The Casparian strip in plant roots is correctly described by which of the following?
A) It aids in the uptake of nutrients.
B) It provides energy for the active transport of minerals into the stele from the cortex.
C) It ensures that all minerals are absorbed from the soil in equal amounts.
D) It ensures that all water and dissolved substances must pass through a cell membrane before
entering the stele.
81) What drives the flow of water through the xylem?
A) passive transport by the endodermis
B) the number of companion cells in the phloem
C) the evaporation of water from the leaves
D) active transport by tracheid and vessel elements
82) What is the main force by which most of the water within xylem vessels moves toward the
top of a tree?
A) active transport of ions into the stele
B) atmospheric pressure on roots
C) evaporation of water through stoma
D) the force of root pressure
83) Most of the water taken up by a plant is
A) used as a solvent.
B) used as a hydrogen source in photosynthesis.
C) lost during transpiration.
D) used to keep cells turgid.
84) Which cells in a root form a protective barrier to the vascular system where all materials
must move through the symplast?
A) pericycle
B) cortex
C) epidermis
D) endodermis
85) The water lost during transpiration is a side effect of the plant’s exchange of gases. However,
the plant derives some benefit from this water loss in the form of
A) evaporative cooling.
B) mineral transport.
C) increased turgor.
D) evaporative cooling and mineral transport.
86) Ignoring all other factors, what kind of day would result in the fastest delivery of water and
minerals to the leaves of a tree?
A) cool, dry day
B) warm, dry day
C) warm, humid day
D) very hot, dry, windy day
87) Which of the following experimental procedures would most likely reduce transpiration
while allowing the normal growth of a plant?
A) subjecting the leaves of the plant to a partial vacuum
B) increasing the level of carbon dioxide around the plant
C) putting the plant in drier soil
D) decreasing the relative humidity around the plant
88) As a biologist, it is your job to look for plants that have evolved structures with a selective
advantage in dry, hot conditions. Which of the following adaptations would be least likely to
meet your objective?
A) CAM plants that grow rapidly
B) small, thick leaves with stomata on the lower surface
C) a thick cuticle on fleshy leaves
D) plants that do not produce abscisic acid and have a short, thick taproot
89) Most of the dry weight of a plant is the result of uptake of
A) water and minerals through root hairs.
B) water and minerals through mycorrhizae.
C) CO2 through stoma.
D) CO2 and O2 through stomata in leaves.
90) Which of the following elemental ions plays a critical role in opening and closing of
stomata?
A) nitrogen
B) potassium
C) magnesium
D) calcium
91) According to the pressure flow hypothesis of phloem transport,
A) solute moves from a high concentration in the source to a lower concentration in the sink.
B) water is actively transported into the source region of the phloem to create the turgor pressure
needed.
C) the combination of a high turgor pressure in the source and transpiration water loss from the
sink moves solutes through phloem conduits.
D) the formation of starch from sugar in the sink increases the osmotic concentration.
92) If you were to prune the shoot tips of a plant, what would be the effect on the plant and the
leaf area index?
A) bushier plants; lower leaf area index
B) tall plants; lower leaf area index
C) short plants; lower leaf area index
D) bushier plants; higher leaf area indexes
93) One is most likely to see guttation in small plants when the
A) transpiration rates are high.
B) root pressure exceeds transpiration pull.
C) preceding evening was hot, windy, and dry.
D) water potential in the stele of the root is high.
94) A young farmer purchases some land in a relatively arid area and is interested in earning a
reasonable profit for many years. Which of the following strategies would best allow the farmer
to achieve such a goal?
A) establishing an extensive irrigation system
B) using plenty of the best fertilizers
C) finding a way to sell all parts of crop plants
D) selecting crops adapted to arid areas
95) Which of the following is of least concern to a researcher in a mineral nutrition experiment?
A) purity of the chemicals used to make the nutrient solutions
B) purity of the water used to make the nutrient solutions
C) ability of a laboratory balance to weigh very small quantities of chemicals
D) medium in which the test seedlings were grown
29.2 Art Questions
In west Texas, cotton has become an important crop in the last several decades. However, in this
hot, dry part of the country there is little rainfall, so farmers irrigate their cotton fields. They
must also regularly fertilize the cotton fields because the soil is very sandy. Figure 29.1 shows
the record of annual productivity (measured in kilograms of cotton per hectare of land) since
1960 in a west Texas cotton field. Use these data to answer the following question(s).
Figure 29.1
1) Based on the information provided in Figure 29.1, what is the most likely cause of the decline
in productivity?
A) The farmer used the wrong kind of fertilizer.
B) The cotton is developing a resistance to the fertilizer and to irrigation water.
C) Water has accumulated in the soil due to irrigation.
D) The soil water potential has become more negative due to salination.
2) If you were the county agriculture agent, what would be the best advice you could give the
farmer who owns the field under study in Figure 29.1?
A) Plant a variety of cotton that requires less water and can tolerate salinity.
B) Continue to fertilize, but stop irrigating the field and rely on rainfall.
C) Continue to irrigate, but stop fertilizing the field and rely on organic nutrients in the soil.
D) Continue to fertilize and irrigate, but add the nitrogen-fixing bacteria Rhizobium to the
irrigation water until the productivity increases.
29.3 Scenario Questions
1) You are conducting an experiment on plant growth. You take a plant fresh from the soil that
weighs 5 kg. Then you dry the plant overnight and determine the dry weight to be 1 kg. Of this
dry weight, how much would you expect to be made up of organic molecules?
A) 1 g
B) 4 g
C) 40 g
D) 960 g
2) Ten tomato plants are germinated and maintained in a large tray with no drainage. After
several weeks they all begin to wilt and die despite repeated watering and fertilization. The most
likely cause of this die-off is
A) competition for resources.
B) anoxia.
C) organic nutrient depletion.
D) no room left for root growth.
3) A greenhouse experiment to test growth rates in tomato cultivars was conducted using sterile
soil mix and watering with sterile solutions of water and fertilizer. Following germination, half
of the plants in each group were transplanted into soil that was obtained from a nearby
agricultural field (nonsterile) and the other half into sterile soil. After several weeks the plants
that were transplanted into nonsterile soil exhibited a much higher growth rate compared to the
plants transplanted into sterile soil. The most likely explanation for this result is
A) the plants transplanted into the nonsterile soil were inoculated with mycorrhizae.
B) the plants transplanted into the nonsterile soil received more fertilizer.
C) the plants transplanted into the sterile soil were stunted due to overfertilization.
D) the plants transplanted into sterile soil suffered anoxia from improper water drainage.
4) Several tomato plants are growing in a small garden plot. If soil water potential were to drop
significantly on a hot summer afternoon, which of the following would most likely occur?
A) Stomatal apertures would decrease.
B) Transpiration would increase.
C) The leaves would become more turgid.
D) The uptake of CO2 would be enhanced.
5) A fellow student brought in a leaf to be examined. The leaf was dark green and thin, had
stoma on the lower surface only, and had a total surface area of 10 square meters. What is the
most likely environment where this leaf was growing?
A) a dry, sandy region
B) a large, still pond
C) a tropical rain forest
D) an oasis within a grassland
6) Plants produce storage products in the form of carbohydrates, proteins, and lipids. Which one
of the following is the backbone element in all these stored products?
A) nitrogen
B) phosphorus
C) hydrogen
D) carbon
29.4 End-of-Chapter Questions
1) Which structure or compartment is part of the symplast?
A) the interior of a vessel element
B) the interior of a sieve tube
C) the cell wall of a mesophyll cell
D) an extracellular air space
2) Which of the following is an adaptation that enhances the uptake of water and minerals by
roots?
A) mycorrhizae
B) cavitation
C) active uptake by vessel elements
D) rhythmic contractions by cortical cells
3) Movement of xylem sap from roots to leaves
A) occurs through the apoplast of sieve-tube elements.
B) usually depends on tension, or negative pressure potential.
C) depends on active transport.
D) depends on the pumping of water through aquaporins.
4) What would enhance water uptake by a plant cell?
A) decreasing the Ψ of the surrounding solution
B) positive pressure on the surrounding solution
C) the loss of solutes from the cell
D) increasing the Ψ of the cytoplasm
5) A plant cell with a ΨS of -0.65 MPa maintains a constant volume when bathed in a solution
that has a ΨS of -0.30 MPa and is in an open container. The cell has a
A) ΨP of +0.65 MPa.
B) Ψ of -0.65 MPa.
C) ΨP of +0.35 MPa.
D) Ψ of 0 MPa.
6) Compared with a cell with few aquaporin proteins in its membrane, a cell containing many
aquaporin proteins will have a
A) faster rate of osmosis.
B) lower water potential.
C) higher water potential.
D) faster rate of active transport.
7) Two groups of tomatoes were grown in the laboratory, one with humus added to the soil and
the other a control without humus. The leaves of the plants grown without humus were yellowish
(less green) compared with those of the plants grown in humus-enriched soil. The best
explanation for this difference is that
A) the healthy plants used carbohydrates in the decomposing leaves of the humus for energy to
make chlorophyll.
B) the humus made the soil more loosely packed, so water penetrated more easily to the roots.
C) the humus contained minerals such as magnesium and iron, needed for the synthesis of
chlorophyll.
D) the heat released by the decomposing leaves of the humus caused more rapid growth and
chlorophyll synthesis.