Question 1

Nitrogen fixation is a process that

Accepted Answer

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. 
E) recycles nitrogen compounds from dead and decaying materials, and converts ammonia to ammonium.

Question 2

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

Accepted Answer

A) Measure the amount of the element stored in plant tissues. 
B) Measure the amount of the element in the soil after plant growth. 
C) Measure the weight of the plant and soil before and after plant growth. 
D) Grow a plant using hydroponics with and without the element.

Question 3

Iron deficiency is often indicated by yellowing in newly formed leaves.This suggests that iron

Accepted Answer

A) is a relatively immobile nutrient in plants. 
B) is tied up in formed chlorophyll molecules. 
C) is concentrated in the xylem of older leaves. 
D) is concentrated in the phloem of older leaves. 
E) is found in leghemoglobin and reduces the amount available to new plant parts.

Question 4

For this pair of items,choose the option that best describes their relationship.
I.the amount of molybdenum in a gram of dried plant material
II.the amount of sulphur in a gram of dried plant material

Accepted Answer

A) Item I is greater than item II. 
B) Item I is less than item II. 
C) Item I is exactly or very approximately equal to item II. 
D) There is not enough information to make a meaningful comparison.

Question 5

Which of the following elements,if increased in concentration,would increase the stability of cell walls?

Accepted Answer

A) zinc 
B) chlorine 
C) calcium 
D) molybdenum 
E) manganese

Question 6

Which of the following elements is incorrectly paired with its function in a plant?

Accepted Answer

A) nitrogen-component of nucleic acids, proteins, hormones, coenzymes 
B) magnesium-component of chlorophyll; activates many enzymes 
C) phosphorus-component of nucleic acids, phospholipids, ATP, several coenzymes 
D) potassium-cofactor functional in protein synthesis, osmosis, operation of stomata 
E) sulphur-component of DNA; activates some enzymes

Question 7

All of the following contributed to the dust bowl in the American southwest during the 1930s except

Accepted Answer

A) overgrazing by cattle. 
B) clear-cutting of forest trees. 
C) plowing of native grasses. 
D) planting of field crops. 
E) lack of soil moisture.

Question 8

A researcher analyzes the mineral content of a particular grass and is surprised to find substantial levels of uranium in both leaf and root tissues.The most likely explanation for this finding is that

Accepted Answer

A) uranium is an essential nutrient for this grass. 
B) the plant has a mutation in its active transport proteins. 
C) there is a higher than usual concentration of uranium in the soil. 
D) uranium is substituting for some other essential nutrient. 
E) uranium is being supplied by mycorrhizae.

Question 9

In hydroponic culture,what is the purpose of bubbling air into the solute?

Accepted Answer

A) to keep dissolved nutrients evenly distributed 
B) to provide oxygen to the root cells 
C) to inhibit the growth of aerobic algae 
D) to inhibit the growth of anaerobic bacteria 
E) to provide CO₂ for photosynthesis

Question 10

Which of the following statements is not true about mycorrhizae?

Accepted Answer

A) Ectomycorrhizae form a dense sheet over the plant root, commonly observed in woody species. 
B) Arbuscular mycorrhizae penetrate cell walls of the root cortex, forming structures called "little trees." 
C) Roots can form a mycorrhizal symbiotic relationship with all species of fungi. 
D) Fungi and bacteria can interact in ways that help plants respond to stressful conditions, such as contaminated soil. 
E) Treating seeds with mycorrhizal fungi can improve crop yield.

Question 11

Rhizobia and mycorrhizae share all of the following features except

Accepted Answer

A) they both benefit by receiving carbohydrate from the plant. 
B) many are host-specific. 
C) they both become parasitic in nutrient-rich environments. 
D) they both enhance the growth of most plants. 
E) they both are found in most ecosystems of the world.

Question 12

If an African violet has chlorosis,which of the following elements might be a useful addition to the soil?

Accepted Answer

A) chlorine 
B) molybdenum 
C) copper 
D) iodine 
E) magnesium

Question 13

Which of the following is a primary difference between ectomycorrhizae and endomycorrhizae?

Accepted Answer

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. 
E) There are no significant differences between ectomycorrhizae and endomycorrhizae.

Question 14

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.The figure below 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 questions.
 
-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 the above figure?

Accepted Answer

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. 
E) Add acid to the soil and increase its cation exchange capabilities so more nutrients are retained in the soil.

Question 15

There are several properties that are characteristic of a soil in which typical plants would grow well.Of the following,which would be the least conducive to plant growth?

Accepted Answer

A) abundant humus 
B) numerous soil organisms 
C) compacted soil 
D) high porosity 
E) high cation exchange capacity

Question 16

Why does overwatering a plant kill it?

Accepted Answer

A) Water does not have all the necessary minerals a plant needs to grow. 
B) Water neutralizes the pH of the soil. 
C) The roots are deprived of oxygen. 
D) Water supports the growth of root parasites. 
E) Water lowers the water potential of the roots.

Question 17

A group of 10 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

Accepted Answer

A) competition for resources. 
B) anoxia. 
C) organic nutrient depletion. 
D) no room left for root growth. 
E) buildup of toxic substances in the tray.

Question 18

In what way do nitrogen compounds differ from other minerals needed by plants?

Accepted Answer

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 needed for protein synthesis. 
D) Only nitrogen is held by cation exchange capacity in the soil. 
E) Only nitrogen can be absorbed by root hairs.

Question 19

Upregulation of leghemoglobin biosynthesis in a leguminous species would most likely indicate

Accepted Answer

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) the plant has been infected with mycorrhizae. 
E) an increase in the biosynthesis of amino acids.

Question 20

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

Accepted Answer

A) energy. 
B) carbohydrates. 
C) lipids and steroids. 
D) minerals. 
E) water.

Exam 37: Soil and Plant Nutrition