Question 1

Which of the following is TRUE of transport in phloem?

Accepted Answer

A) It occurs from sink to source. 
B) It only occurs from leaves to roots. 
C) It moves materials down the plant body. 
D) It is driven by turgor pressure. 
E) It is usually a passive process. 
A) It occurs from sink to source. 
B) It only occurs from leaves to roots. 
C) It moves materials down the plant body. 
D) It is driven by turgor pressure. 
E) It is usually a passive process.

Question 2

If the concentrations of CO2 and O2 were equal in the atmosphere, rubisco would favor CO2 over O2 as a substrate by about 2000:1 at 25°C. Why, in today's atmosphere (and at 25°C), is the photosynthesis/photorespiration ratio of C3 plants only about 4:1?

Accepted Answer

A) O2 is much more abundant than CO2 in today's atmosphere. 
B) Rubiscos that are more selective for CO2 are slower. 
C) O2 is continually produced in the leaves of C4 plants. 
D) RuBP reacts readily with O2. 
A) O2 is much more abundant than CO2 in today's atmosphere. 
B) Rubiscos that are more selective for CO2 are slower. 
C) O2 is continually produced in the leaves of C4 plants. 
D) RuBP reacts readily with O2.

Question 3

Many bryophytes have to be able to tolerate desiccation because they:

Accepted Answer

A) dry out with the environment. 
B) have little water storage capacity. 
C) are restricted to sunny habitats. 
D) are restricted to saline habitats. 
A) dry out with the environment. 
B) have little water storage capacity. 
C) are restricted to sunny habitats. 
D) are restricted to saline habitats.

Question 4

Why have many plants (i.e., C4 plants) developed ways to limit or avoid photorespiration?

Accepted Answer

A) Photorespiration results in a net loss of metabolic energy. 
B) Photorespiration requires enormous amounts of oxygen. 
C) Photorespiration requires an enormous amount of water. 
D) Photorespiration results in a net loss of carbohydrate. 
A) Photorespiration results in a net loss of metabolic energy. 
B) Photorespiration requires enormous amounts of oxygen. 
C) Photorespiration requires an enormous amount of water. 
D) Photorespiration results in a net loss of carbohydrate.

Question 5

Why do plants need an endodermis in their roots?

Accepted Answer

A) to control the movement of dissolved ions into the xylem that would otherwise 
B) concentrate in the shoot as a consequence of evaporation 
C) to exclude mycorrhizal symbionts from access to the phloem 
D) to keep air bubbles from entering the xylem 
E) All of these choices are correct. 
A) to control the movement of dissolved ions into the xylem that would otherwise 
B) concentrate in the shoot as a consequence of evaporation 
C) to exclude mycorrhizal symbionts from access to the phloem 
D) to keep air bubbles from entering the xylem 
E) All of these choices are correct.

Question 6

During photorespiration, which of the following molecules acts as a substrate for the rubisco enzyme?

Accepted Answer

A) CO2 
B) O2 
C) H2O 
D) N2 
A) CO2 
B) O2 
C) H2O 
D) N2

Question 7

Some plant nutrients are more mobile in soil than others.

Accepted Answer

A) True 
 B)False

Question 8

Which of the following statements is NOT true of nitrogen-fixing bacteria?

Accepted Answer

A) They live in root nodules. 
B) They are very common in symbioses with plants from the legume family. 
C) They are very common in symbioses in all plant families. 
D) Some are free-living in the soil. 
E) They provide an important way that biologically available nitrogen enters ecosystems. 
A) They live in root nodules. 
B) They are very common in symbioses with plants from the legume family. 
C) They are very common in symbioses in all plant families. 
D) Some are free-living in the soil. 
E) They provide an important way that biologically available nitrogen enters ecosystems.

Question 9

A botanist extracts the contents of a plant's vasculature. Upon analysis, she finds that these contents contain both ions and RNA. The botanist likely targeted a:

Accepted Answer

A) sieve tube. 
B) tracheid. 
C) vessel. 
D) tracheid and a vessel. 
E) sieve tube, a tracheid, and a vessel. 
A) sieve tube. 
B) tracheid. 
C) vessel. 
D) tracheid and a vessel. 
E) sieve tube, a tracheid, and a vessel.

Question 10

To avoid losing, due to cavitation, the ability to pull water from the soil, plants:

Accepted Answer

A) have parallel water conduits. 
B) generate high tensile or pulling forces in the xylem. 
C) cannot occupy certain habitats. 
D) close stomata to limit the tensions in the xylem. 
A) have parallel water conduits. 
B) generate high tensile or pulling forces in the xylem. 
C) cannot occupy certain habitats. 
D) close stomata to limit the tensions in the xylem.

Question 11

In C4 plants, photosynthesis operates more quickly and with less need for widely open stomata than in C3 plants. What characteristics of the enzyme PEP carboxylase are responsible for these differences?

Accepted Answer

A) PEP carboxylase is located in the cytoplasm, so it is in closer contact with its substrate than rubisco, which is located in the chloroplast. 
B) PEP carboxylase has a higher catalytic rate than rubisco, which results in an increase in CO2 concentrations in bundle-sheath cells. 
C) PEP carboxylase is a much smaller enzyme than rubisco and, therefore, is present at much higher concentrations in C4 plant cells. 
D) PEP carboxylase is not consumed in its reaction with HCO3-. 
A) PEP carboxylase is located in the cytoplasm, so it is in closer contact with its substrate than rubisco, which is located in the chloroplast. 
B) PEP carboxylase has a higher catalytic rate than rubisco, which results in an increase in CO2 concentrations in bundle-sheath cells. 
C) PEP carboxylase is a much smaller enzyme than rubisco and, therefore, is present at much higher concentrations in C4 plant cells. 
D) PEP carboxylase is not consumed in its reaction with HCO3-.

Question 12

Which of the following statements BEST defines cavitation?

Accepted Answer

A) Cavitation is the formation and expansion of gas bubbles in the xylem. 
B) Cavitation is the presence of sugars in the xylem. 
C) Cavitation describes the process of xylem vessel collapse. 
D) Cavitation is the presence of ice in the xylem. 
E) Cavitation is the presence of pressure in the xylem. 
A) Cavitation is the formation and expansion of gas bubbles in the xylem. 
B) Cavitation is the presence of sugars in the xylem. 
C) Cavitation describes the process of xylem vessel collapse. 
D) Cavitation is the presence of ice in the xylem. 
E) Cavitation is the presence of pressure in the xylem.

Question 13

Before the development of the Haber-Bosch process, NHS1U1B13S1U1B0 could be produced from NS1U1B12S1U1B0 by:

Accepted Answer

A) fungi. 
B) plants. 
C) prokaryotes. 
D) respiration. 
A) fungi. 
B) plants. 
C) prokaryotes. 
D) respiration.

Question 14

When stomata are open and a plant is transpiring normally, water moves from the soil into the root xylem:

Accepted Answer

A) due to the action of ATP driven pumps in the endodermis. 
B) without the plant doing any additional work on the fluid. 
C) due to a force generated by the partial dehydration of cell walls in leaves. 
D) in a flow that is ultimately driven by evaporation from the shoot. 
A) due to the action of ATP driven pumps in the endodermis. 
B) without the plant doing any additional work on the fluid. 
C) due to a force generated by the partial dehydration of cell walls in leaves. 
D) in a flow that is ultimately driven by evaporation from the shoot.

Question 15

Roots elongate continuously in order to:

Accepted Answer

A) mine new regions of soil for nutrients. 
B) act as a carbohydrate sink. 
C) obtain O2. 
A) mine new regions of soil for nutrients. 
B) act as a carbohydrate sink. 
C) obtain O2.

Question 16

The volume of phloem tissue in a stem is typically much smaller than the volume of xylem tissue because:

Accepted Answer

A) the pressure gradient driving water flow in the phloem is metabolically generated and, therefore, can be much larger than the environmentally generated xylem gradient. 
B) phloem conduits are much wider, and because flow is proportional to conduit radius raised to the fourth power, fewer phloem conduits are needed. 
C) xylem dies quickly and, therefore, needs to be replaced frequently. 
D) plants lose hundreds of H2O molecules for each CO2 gained. 
A) the pressure gradient driving water flow in the phloem is metabolically generated and, therefore, can be much larger than the environmentally generated xylem gradient. 
B) phloem conduits are much wider, and because flow is proportional to conduit radius raised to the fourth power, fewer phloem conduits are needed. 
C) xylem dies quickly and, therefore, needs to be replaced frequently. 
D) plants lose hundreds of H2O molecules for each CO2 gained.

Question 17

Which of the following statements is CORRECT regarding C4 plants as compared with CAM plants?

Accepted Answer

A) In C4 plants, CO2 capture and the Calvin cycle happen in different cell types, whereas in CAM plants CO2 capture and the Calvin cycle happen at different times. 
B) In C4 plants, CO2 capture and the Calvin cycle happen at different times, whereas in CAM plants CO2 capture and the Calvin cycle happen in different cell types. 
C) C4 plants produce a 4-carbon organic acid as a storage form, whereas CAM plants produce a 4-carbon inorganic acid as a storage form. 
D) C4 plants do not require additional ATP relative to C3 plants, whereas CAM plants do require additional ATP relative to C3 plants. 
E) C4 plants are found in hot, sunny environments, whereas CAM plants are found in moist, cool environments. 
A) In C4 plants, CO2 capture and the Calvin cycle happen in different cell types, whereas in CAM plants CO2 capture and the Calvin cycle happen at different times. 
B) In C4 plants, CO2 capture and the Calvin cycle happen at different times, whereas in CAM plants CO2 capture and the Calvin cycle happen in different cell types. 
C) C4 plants produce a 4-carbon organic acid as a storage form, whereas CAM plants produce a 4-carbon inorganic acid as a storage form. 
D) C4 plants do not require additional ATP relative to C3 plants, whereas CAM plants do require additional ATP relative to C3 plants. 
E) C4 plants are found in hot, sunny environments, whereas CAM plants are found in moist, cool environments.

Question 18

Photorespiration:

Accepted Answer

A) is a process similar to cellular respiration, producing energy for plants. 
B) occurs in equal parts with photosynthesis. 
C) drives photosynthesis. 
D) generates ATP. 
E) is due to rubisco being able to bind O2 as well as CO2. 
A) is a process similar to cellular respiration, producing energy for plants. 
B) occurs in equal parts with photosynthesis. 
C) drives photosynthesis. 
D) generates ATP. 
E) is due to rubisco being able to bind O2 as well as CO2.

Question 19

In many plants, it is possible to peel off the lower epidermis of a leaf without disturbing the photosynthetic mesophyll cells, thereby exposing the mesophyll directly to the air. What would you expect the immediate (seconds to minutes) response of photosynthesis to be? What would you expect the longer-term (minutes to hours) response of photosynthesis to be?

Accepted Answer

A) immediate increase, long-term decrease 
B) immediate decrease, long-term increase 
C) no change immediately, long-term decrease 
D) no change immediately, long-term increase 
A) immediate increase, long-term decrease 
B) immediate decrease, long-term increase 
C) no change immediately, long-term decrease 
D) no change immediately, long-term increase

Question 20

What factors influence the rate of CO2 diffusion into a leaf?

Accepted Answer

A) the CO2 concentration outside the leaf 
B) the rate at which photosynthesis is occurring 
C) the extent to which the stomata are open 
D) All of these choices are correct. 
A) the CO2 concentration outside the leaf 
B) the rate at which photosynthesis is occurring 
C) the extent to which the stomata are open 
D) All of these choices are correct.

Exam 29: Plant Structure and Function: Moving Photosynthesis Onto Land

Which of the following is TRUE of transport in phloem?

If the concentrations of CO2 and O2 were equal in the atmosphere, rubisco would favor CO2 over O2 as a substrate by about 2000:1 at 25°C. Why, in today's atmosphere (and at 25°C), is the photosynthesis/photorespiration ratio of C3 plants only about 4:1?

Many bryophytes have to be able to tolerate desiccation because they:

Why have many plants (i.e., C4 plants) developed ways to limit or avoid photorespiration?

Why do plants need an endodermis in their roots?

During photorespiration, which of the following molecules acts as a substrate for the rubisco enzyme?

Some plant nutrients are more mobile in soil than others.

Which of the following statements is NOT true of nitrogen-fixing bacteria?

A botanist extracts the contents of a plant's vasculature. Upon analysis, she finds that these contents contain both ions and RNA. The botanist likely targeted a:

To avoid losing, due to cavitation, the ability to pull water from the soil, plants:

In C4 plants, photosynthesis operates more quickly and with less need for widely open stomata than in C3 plants. What characteristics of the enzyme PEP carboxylase are responsible for these differences?

Which of the following statements BEST defines cavitation?

Before the development of the Haber-Bosch process, NH3 could be produced from N2 by:

When stomata are open and a plant is transpiring normally, water moves from the soil into the root xylem:

Roots elongate continuously in order to:

The volume of phloem tissue in a stem is typically much smaller than the volume of xylem tissue because:

Which of the following statements is CORRECT regarding C4 plants as compared with CAM plants?

Photorespiration:

What factors influence the rate of CO2 diffusion into a leaf?

Life: Chemical, Cellular, and Evolutionary Foundations

The Molecules of Life

Nucleic Acids and Transcription

Translation and Protein Structure

Organizing Principles: Lipids, Membranes, and Cell Compartments

Making Life Work: Capturing and Using Energy

Cellular Respiration: Harvesting Energy From Carbohydrates and Other Fuel Molecules

Photosynthesis: Using Sunlight to Build Carbohydrates

Cell Signaling

Cell and Tissue Architecture: Cytoskeleton, Cell Junctions, and Extracellular Matrix

Cell Division: Variations, Regulation, and Cancer

Dna Replication and Manipulation

Genomes

Mutation and Dna Repair

Genetic Variation

Mendelian Inheritance

Inheritance of Sex Chromosomes, Linked Genes, and Organelles

The Genetic and Environmental Basis of Complex Traits

Genetic and Epigenetic Regulation

Genes and Development

Evolution: How Genotypes and Phenotypes Change Over Time

Species and Speciation

Evolutionary Patterns: Phylogeny and Fossils

Human Origins and Evolution

Cycling Carbon

Bacteria and Archaea

Eukaryotic Cells: Origins and Diversity

Being Multicellular

Plant Reproduction: Finding Mates and Dispersing Young

Plant Growth and Development

Plant Defense: Keeping the World Green

Plant Diversity

Fungi: Structure, Function, and Diversity

Animal Nervous Systems

Animal Sensory Systems and Brain Function

Animal Movement: Muscles and Skeletons

Animal Endocrine Systems

Animal Cardiovascular and Respiratory Systems

Animal Metabolism, Nutrition, and Digestion

Animal Renal Systems: Water and Waste

Animal Reproduction and Development

Animal Immune Systems

Animal Diversity

Animal Behavior

Population Ecology

Species Interactions, Communities, and Ecosystems

Biomes and Global Ecology

The Anthropocene: Humans As a Planetary Force

Filters

If the concentrations of CO₂ and O₂ were equal in the atmosphere, rubisco would favor CO₂ over O₂ as a substrate by about 2000:1 at 25°C. Why, in today's atmosphere (and at 25°C), is the photosynthesis/photorespiration ratio of C₃ plants only about 4:1?

Why have many plants (i.e., C₄ plants) developed ways to limit or avoid photorespiration?

In C₄ plants, photosynthesis operates more quickly and with less need for widely open stomata than in C₃ plants. What characteristics of the enzyme PEP carboxylase are responsible for these differences?

Before the development of the Haber-Bosch process, NH₃ could be produced from N₂ by:

Which of the following statements is CORRECT regarding C₄ plants as compared with CAM plants?

What factors influence the rate of CO₂ diffusion into a leaf?