Chapter 37 Questions

Question 1

What soil composition would be best for availability of nutrients, water, and root development?

a. higher proportion of clay; lower amounts of humus and sand
b. equal amounts of sand, clay, and humus
c. higher proportion of sand; lower amount of humus and clay
d. higher proportion of humus; lower amounts of clay and sand

Answer 1

d. higher proportion of humus; lower amounts of clay and sand

Question 2

The highest amount of oxygen will be found in soils containing large amounts of ___.

a. clay
b. silt
c. sand
d. gravel

Answer 2

d. gravel

Question 3

A group of 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. organic nutrient depletion
b. no room left for root growth
c. competition for resources
d. a lack of oxygen for the roots

Answer 3

d. a lack of oxygen for the roots

Question 4

Which of the following soil minerals is most likely leached away during a hard rain?

a. K+
b. Na+
c. NO3-
d. Ca++

Answer 4

c. NO3-

Question 5

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. selecting crops adapted to arid areas
c. using plenty of the best fertilizers
d. finding a way to sell all parts of crop plants

Answer 5

b. selecting crops adapted to arid areas

Question 6

Which of the following would be the most effective strategy to remove toxic heavy metals from a soil?

a. inoculating soil with mycorrhizae to avoid heavy-metal uptake
b. adding plant species that have the ability to take up and accumulate heavy metals
c. heavy irrigation to leach out the heavy metals
d. application of sulfur to lower the soil pH and precipitate the heavy metals

Answer 6

b. adding plant species that have the ability to take up and accumulate heavy metals

Question 7

How would you expect the root system of a plant grown by hydroponics to compare to the root system of a plant grown in soil? The root system of a plant grown by hydroponics would be ___.

a. more developed
b. absent
c. about the same
d. less developed

Answer 7

d. less developed

Question 8

Which of the following experiments is the best way to determine if an element is essential for plant growth?

a. Measure the weight of the plant and soil before and after plant growth.
b. Measure the amount of the element stored in plant tissues.
c. Grow a plant using hydroponics with and without the element.
d. Measure the amount of the element in the soil after plant growth.

Answer 8

c. Grow a plant using hydroponics with and without the element.

Question 9

Synthesis of which of the following compounds in a mature leaf would be least impacted by a temporary soil nitrogen deficiency?

a. cellulose
b. amino acids
c. DNA
d. RNA

Answer 9

a. cellulose

Question 10

Two groups of tomatoes were grown under laboratory conditions, one with humus added to the soil, and one a control without humus. The leaves of the plants grown without humus were yellowish (less green) compared with those of the plants grown in the humus-enriched soil. The best explanation for this difference is that ____.

a. the humus contained minerals such as magnesium and iron, needed for the synthesis of chlorophyll
b. the heat released by the decomposing leaves of the humus caused more rapid growth and chlorophyll synthesis
c. the healthy plants used the food in the decomposing leaves of the humus for energy to make chlorophyll
d. the humus made the soil more loosely packed, so water penetrated more easily to the roots

Answer 10

a. the humus contained minerals such as magnesium and iron, needed for the synthesis of chlorophyll

Question 11

Soil leaching can cause nutrient deficiencies in the soil.  Which of the following are symptoms of nutrient deficiency in plants?
I. chlorosis
II. death of meristems
III. excess storage of chlorophyll
IV. small internodes
a. II, III, and IV
b. I, II, and III
c. I, II, III, and IV
d. I, II, and IV

Answer 11

d. I, II, and IV

Question 12

Why is nitrogen fixation an essential process?

a. Nitrogen fixation is very expensive in terms of metabolic energy.
b. Nitrogen fixers are sometimes symbiotic with legumes.
c. Fixed nitrogen is often the limiting factor in plant growth.
d. Nitrogen fixation can only be done by certain prokaryotes.

Answer 12

c. Fixed nitrogen is often the limiting factor in plant growth.

Question 13

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. are developing offshoots from the root
b. are infected with a parasite
c. are benefiting from a mutualistic bacterium
d. suffer from a mineral deficiency

Answer 13

c. are benefiting from a mutualistic bacterium

Question 14

The specific relationship between a legume and its mutualistic Rhizobium strain probably depends on ___.

a. specific recognition between the chemical signals and signal receptors of the Rhizobium strain and legume species
b. each legume being found where the soil has only the Rhizobium specific to that legume
c. each Rhizobium strain having a form of nitrogenase that works only in the appropriate legume host
d. each legume having a chemical dialogue with a fungus

Answer 14

a. specific recognition between the chemical signals and signal receptors of the Rhizobium strain and legume species

Question 15

The earliest vascular plants on land had underground stems (rhizomes(, but no roots. Water and mineral nutrients were most likely obtained by ___.

a. diffusion through stomata
b. osmosis through the root hairs
c. absorption by mycorrhizae
d. diffusion across the cuticle of the rhizome

Answer 15

c. absorption by mycorrhizae

Question 16

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. Proton pumps reversed the membrane potential.
c. Mycorrhizal fungi were killed.
d. Active transport of minerals was inhibited.

Answer 16

c. Mycorrhizal fungi were killed.

Question 17

We would expect the greatest difference in plant health between two groups of plants of the same species, one group with mycorrhizae and one group without mycorrhizae, in an environment ___.

a. in which the soil is relatively deficient in mineral nutrients
b. where nitrogen-fixing bacteria are abundant
c. that has soil with poor drainage
d. that is near a body of water, such as a pond or river

Answer 17

a. in which the soil is relatively deficient in mineral nutrients

Question 18

While hiking in a forest, you notice an unusual plant growing on the branches of a tree. What will help you to determine if this plant is epiphytic or parasitic?

a. If the plant is green, it is epiphytic; if not, then it is parasitic.
b. The epiphytic plant will have large water-collecting leaves, and the parasitic plant will not.
c. The root of an epiphytic plant will be in the soil, but a parasitic plant will grow from the trunk of a tree.
d. The roots of a parasitic plant will penetrate under the bark into the tree xylem, and the roots of epiphytic plant will not.

Answer 18

d. The roots of a parasitic plant will penetrate under the bark into the tree xylem, and the roots of epiphytic plant will not.

Question 19

The difference between macronutrients and micronutrients is that _____.

a. the molecules of macronutrients are larger than those of micronutrients
b. macronutrients are essential for physiological function of plants, while micronutrients amplify plant growth if they are available
c. macronutrients are needed for growth, while micronutrients are needed only for reproduction
d. macronutrients are required by plants in larger quantities than are micronutrients
e. the molecules of macronutrients move through the symplast, and micronutrients can move through either the symplast or the apoplast

Answer 19

d. macronutrients are required by plants in larger quantities than are micronutrients

Question 20

Legumes (such as soybeans) commonly obtain their nitrogen through a mutualistic association with _____.

a. nitrifying bacteria, which oxidize ammonium to nitrite
b. ammonifying bacteria, which convert organic nitrogen to ammonium
c. denitrifying bacteria, which convert organic nitrite to ammonium
d. nitrifying bacteria, which extract nitrogen from decomposing animals
e. nitrogen-fixing bacteria, which convert gaseous nitrogen to ammonium

Answer 20

e. nitrogen-fixing bacteria, which convert gaseous nitrogen to ammonium

Question 21

Which statement most accurately reflects the interaction between plants and the soil in the rhizosphere in which they grow?

a. Plants passively take up nitrogen from the soil with their roots, interacting little with the rhizosphere.
b. Plants obtain nitrogen through a symbiotic interaction with rhizosphere bacteria.
c. Plants’ ability to absorb nitrogen is compromised due to high concentrations of bacteria in the rhizosphere.
d. Rhizosphere bacteria form chains of cells that penetrate the plant root and facilitate plant nitrogen absorption through capillary action.

Answer 21

b. Plants obtain nitrogen through a symbiotic interaction with rhizosphere bacteria.

Question 22

Which is least likely to limit the availability of soil nutrients to a plant?

a. the types of minerals present in the soil
b. the pH of the soil
c. the texture of the soil
d. the presence or absence of certain types of microorganisms in the soil
e. the permeability of its epidermal cell walls to nutrients

Answer 22

e. the permeability of its epidermal cell walls to nutrients

Question 23

Phytoremediation differs from traditional soil remediation in that it attempts to _____.

a. change the composition of soil microbes to one that enhances crop growth
b. remove pollutants from the soil through their accumulation in plant material that can be removed
c. use secretion of chelators by plants to bind up specific toxins found in the soil
d. have plants remove dangerous soil microbes by taking them into vesicles and digesting them
e. use cover crops and “green manures” to limit the rates of topsoil loss through erosion

Answer 23

b. remove pollutants from the soil through their accumulation in plant material that can be removed

Question 24

Which is not a correct statement about how plants often use mineral nutrients?

a. They may be used as cofactors in enzyme-catalyzed reactions.
b. They may be involved in essential steps of the light reactions of photosynthesis.
c. Those minerals taken from the soil account for most of the mass of organic matter the plant will make.
d. Some of these minerals can act as second messengers in signal transduction systems.
e. Some mineral nutrients might be accumulated or expelled as a cell attempts to regulate the concentration of its osmotically active substances.

Answer 24

c. Those minerals taken from the soil account for most of the mass of organic matter the plant will make.

Question 25

Which statement about how some plants benefit from the presence of soil microbes is incorrect?

a. Through their mycorrhizal interactions with fungi, plant roots can acquire needed nutrients.
b. Plants sometimes obtain organic molecules from some of the bacteria or fungi they encounter in the soil.
c. The antibiotics created by some soil microbes can help protect the plant root from some pathogens.
d. Mycorrhizae allow some plant roots to live in anaerobic soils.
e. Some bacteria can convert nitrogen into a form plants can more readily take up and use.

Answer 25

d. Mycorrhizae allow some plant roots to live in anaerobic soils.

Question 26

In the formation of a root nodule, which step normally occurs first?

a. Bacteria produce “nod factors.”
b. The infection thread is formed.
c. Plant roots secrete signals that attract Rhizobium.
d. Vascular connections to the nodule are established.
e. Vesicles, in which Rhizobium lives, are formed in the plant cells.

Answer 26

c. Plant roots secrete signals that attract Rhizobium.

Question 27

Which statement about soil nutrients and how plants acquire them is correct?

a. The production and release of O2 by plant roots can enhance the activity of microbes in the soil.
b. The need to take up certain ions can be a significant metabolic cost for plants.
c. The acidification of the soil by proton pumping by the plant’s root cells can cause the soil to hold various anions less tightly and thus make them more available to the plant.
d. The soil particles cannot hold cationic minerals very well, so they are often carried out of the soil in water that flows through it.
e. Plants rarely make use of the actions of other species to help them obtain soil nutrients.

Answer 27

b. The need to take up certain ions can be a significant metabolic cost for plants.

Question 28

What percentage of plants form some kind of mycorrhizal association?

a. 10%
b. 20%
c. 50%
d. 70%
e. 95%

Answer 28

e. 95%

Question 29

Which is not a macronutrient needed by plants?

a. Mg
b. Ca
c. K
d. Al
e. Cl

Answer 29

d. Al

Question 30

In the cycling of nitrogen through ecosystems, what immediately precedes nitrogen fixation?

a. ammonification
b. denitrification
c. weathering
d. mineral decomposition
e. nitrification

Answer 30

b. denitrification

Question 31

Too many nutrients can be toxic. An excess of minerals in the soil is an example of _____.

a. nitrification
b. mutualism
c. salinization
d. fertilization
e. none of the above

Answer 31

c. salinization

Question 32

The inorganic nutrient most often lacking in crops is

a. carbon.
b. nitrogen.
c. phosphorus.
d. potassium.

Answer 32

b. nitrogen.

Question 33

Micronutrients are needed in very small amounts because

a. most of them are mobile in the plant.
b. most serve mainly as cofactors of enzymes.
c. most are supplied in large enough quantities in seeds.
d. they play only a minor role in the growth and health of the plant.

Answer 33

b. most serve mainly as cofactors of enzymes.

Question 34

Mycorrhizae enhance plant nutrition mainly by

a. absorbing water and minerals through the fungal hyphae.
b. providing sugar to root cells, which have no chloroplasts.
c. converting atmospheric nitrogen to ammonia.
d. enabling the roots to parasitize neighboring plants.

Answer 34

a. absorbing water and minerals through the fungal hyphae.

Question 35

Epiphytes are

a. fungi that attack plants.
b. fungi that form mutualistic associations with roots.
c. nonphotosynthetic parasitic plants.
d. plants that grow on other plants.

Answer 35

d. plants that grow on other plants.

Question 36

Some of the problems associated with intensive irrigation include all of the following except

a. soil salinization.
b. overfertilization.
c. land subsidence.
d. aquifer depletion.

Answer 36

b. overfertilization.

Question 37

A mineral deficiency is likely to affect older leaves more than younger leaves if

a. the mineral is a micronutrient.
b. the mineral is very mobile within the plant.
c. the mineral is required for chlorophyll synthesis.
d. the mineral is a macronutrient.

Answer 37

b. the mineral is very mobile within the plant.

Question 38

The greatest difference in health between two groups of plants of the same species, one group with mycorrhizae and one group without mycorrhizae, would be in an environment

a. where nitrogen-fixing bacteria are abundant.
b. that has soil with poor drainage.
c. that has hot summers and cold winters.
d. in which the soil is relatively deficient in mineral nutrients.

Answer 38

d. in which the soil is relatively deficient in mineral nutrients.

Question 39

Two groups of tomatoes were grown under laboratory conditions, one with humus added to the soil and one 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 is that

a. the healthy plants used the food 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.

Answer 39

c. the humus contained minerals such as magnesium and iron needed for the synthesis of chlorophyll.

Question 40

The specific relationship between a legume and its mutualistic Rhizobium strain probably depends on

a. each legume having a chemical dialogue with a fungus.
b. each Rhizobium strain having a form of nitrogenase that works only in the appropriate legume host.
c. each legume being found where the soil has only the Rhizobium specific to that legume.
d. specific recognition between chemical signals and signal receptors of the Rhizobium strain and legume species.

Answer 40

d. specific recognition between chemical signals and signal receptors of the Rhizobium strain and legume species.