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

Question 1

Which of the following are classified as land plants, but not as vascular plants?

A)gymnosperms
B)angiosperms
C)lycophytes
D)liverworts
E)algae

Answer 1

D

Question 2

How do bryophytes avoid damage to their tissues from a dry environment?

A)They use roots to extract water from the soil, and so avoid desiccation.
B)They use vascular tissue to transport water, and so avoid desiccation.
C)Their membranes are able to withstand the desiccation and re-hydration of the cells without rupturing.
D)They do not have a mechanism to survive desiccation, and so dry out and die.
E)They are able to store water in specialized tissues in their leaves.

Answer 2

C

Question 3

If an ancestral plant produced several hundred descendants over millions of years, a monophyletic group would contain _____ of those descendants, and a paraphyletic group would contain _____ of those descendants.

A)all; all
B)a subset; all
C)all; a subset
D)none; all
E)all; none

Answer 3

C

Question 4

Similar to bryophytes, the leaves of most angiosperms also demonstrate desiccation tolerance and can survive long periods without water.

Question 5

Referring to Figure 29.1, vascular tissue first evolved in which lineage of extant land plants?

A)mosses
B)bryophytes
C)lycophytes
D)gymnosperms
E)hornworts

Question 6

One of the earliest evolutionary adaptations that helps plants to retain water in a terrestrial environment is the:

A)leaf.
B)xylem.
C)phloem.
D)root.
E)cuticle.

Question 7

Vascular plants hydrate photosynthetic cells using _____, whereas bryophytes do so using _____.

A)surface water; soil water
B)soil water; surface water
C)xylem; phloem
D)xylem; surface water

Question 8

Consider the three soil water profiles (A, B,

A)alternates temporally between B and C.
B)varies spatially between A and C.
C)alternates temporally between A and B.
C)in the figure below. You would expect bryophytes instead of vascular plants to be the dominant type of plant in environments for which the soil water profile:

D)is constantly C.

Question 9

Land plants are descended from:

A)mosses.
B)green algae.
C)cyanobacteria.
D)brown algae.

Question 10

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

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 11

You may know that Ernest Shackleton was a famous explorer of Antarctica. What plants would he most likely have encountered as he traveled the Antarctic?

A)ferns and horsetails
B)lycophytes
C)bryophytes
D)angiosperms
E)gymnosperms

Question 12

Although bryophytes do not have roots, they do possess rootlike hairs that contain rudimentary phloem and xylem.

Question 13

Bryophytes are able to pull water from the soil.

Question 14

Which of the following would be classified as a vascular plant?

A)a rosebush
B)a portobello mushroom
C)peat moss
D)an evergreen tree

Question 15

Referring to Figure 29.1, which of the following would NOT be considered a monophyletic group?

A)ferns/horsetails
B)angiosperms
C)gymnosperms
D)bryophytes
E)ferns/horsetails and bryophytes

Question 16

Bryophytes are found:

A)where roots do not provide an advantage.
B)throughout the world.
C)where vascular plants do not have a competitive advantage.
D)on rocks and tree trunks.
E)All of these choices are correct.

Question 17

During both CAM and C₄ photosynthesis, what is the role of the PEP carboxylase enzyme?

A)to create ATP
B)to capture CO₂ in the form of HCO₃
C)to capture CO₂ in the form of 3-carbon organic acids
D)to capture CO₂ in the form of 4-carbon organic acids

Question 18

Bryophytes are widely distributed geographically, but vascular plants account for most terrestrial photosynthesis. Why?

A)Bryophyte photosynthesis depends on surface water.
B)Vascular plants can maintain the hydration of photosynthetic cells using deep soil water.
C)Vascular plants are larger CO₂ sinks than bryophytes.

Question 19

Which of the following plants would likely be the FIRST to colonize a newly formed volcanic island (an environment of bare rock with no developed soil)?

A)vascular plants
B)lycophytes
C)bryophytes
D)gymnosperms

Question 20

Referring to Figure 29.1, which of the following are NOT a monophyletic group?

A)ferns
B)gymnosperms
C)angiosperms
D)lycophytes

Question 21

Plants lose a great deal of water from their leaves in a process referred to as:

A)transformation.
B)transpiration.
C)transduction.
D)transfection.

Question 22

Which of the following statements is TRUE regarding CO₂ capture and the Calvin cycle in CAM plants?

A)CO₂ capture occurs at night, and the Calvin cycle takes place in the day.
B)CO₂ is captured in mesophyll cells, and the Calvin cycle occurs in bundle-sheath cells.
C)CO₂ capture and the Calvin cycle both occur in the same cell.
D)CO₂ capture and the Calvin cycle both occur during the day (in sunlight).

Question 23

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?

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 24

You are evaluating novel varieties of C₃ rice that express PEP carboxylase and rubisco in both mesophyll and bundle-sheath cells for a project to develop rice plants that are capable of C₄ photosynthesis. Your MOST promising candidates are those for which the enzyme levels of:

A)both enzymes are higher in bundle-sheath cells than in mesophyll cells.
B)PEP carboxylase levels are higher in mesophyll cells than in bundle-sheath cells.
C)rubisco levels are lower in bundle-sheath cells than in mesophyll cells.
D)both enzymes are highly expressed in both cell types.

Question 25

CAM plants do NOT operate the Calvin cycle at night because:

A)chloroplasts require sunlight to produce ATP and NADPH.
B)PEP carboxylase is only active in darkness.
C)CAM plants capture HCO₃^-, but the Calvin cycle requires CO₂.
D)CAM plants close their stomata during the day.

Question 26

Openings between _____ cells create pores in the leaf epidermis that play a critical role in photosynthesis by providing openings for atmospheric CO₂ to enter a leaf's interior.

A)guard
B)bundle-sheath
C)companion
D)mesophyll

Question 27

If a phylogenetic group is composed of all the descendants of a single ancestor, then that group would be considered paraphyletic.

Question 28

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?

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 29

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

A)CO₂
B)O₂
C)H₂O
D)N₂

Question 30

Which of the following plants are NOT bryophytes?

A)mosses
B)liverworts
C)ferns
D)hornworts
E)liverworts and hornworts

Question 31

You are growing C₃ and C₄ plants in normal (21%) and low (1%) O₂ air, under both warm, well-lit conditions and cool, shady conditions. You find that, in general, the C₃ plants have a photosynthetic advantage over C₄ plants in:

A)warm high light at 1% O₂ and cool shade at 21% O₂ only.
B)cool shade under 21% and 1% O₂, and in warm high light at 1% O_2.
C)cool shade at 21% O₂ and warm high light at 21% O_2.
D)warm high light at 21% O₂ and 1% O₂, and cool shade at 21% O_2.

Question 32

C₄ plants are usually _____ in shady habitats because C₄ photosynthesis has _____ ATP requirements than the C₃ pathway.

A)common; lower
B)common; higher
C)rare; lower
D)rare; higher

Question 33

Consider a plant growing in well-watered soil and high light in a small glass chamber. How will the plant respond if you exhale repeatedly into the chamber?

A)stomata will close even as photosynthesis increases
B)stomata will close and so photosynthesis declines
C)stomata do not respond, but photosynthesis increases
D)stomata will open in response to O₂ buildup

Question 34

How would subjecting a CAM plant at night to normal daytime temperatures affect its water use efficiency (CO₂ captured /H₂O lost)?

A)CO₂ capture would increase, due to a temperature-induced increase in PEP carboxylase activity, which is enough to increase water use efficiency.
B)CO₂ capture would decrease due to temperature inhibition of rubisco, which would decrease water use efficiency.
C)Water use efficiency would decrease due to an increasing concentration gradient for diffusion of water out of the leaf at night.
D)Water use efficiency would increase due to more rapid diffusion of CO₂ during the day.

Question 35

In C₄ plants, the Calvin cycle is performed in _____; CO₂ is captured during the C₄ cycle in _____.

A)the day; the night
B)mesophyll cells; bundle-sheath cells
C)bundle-sheath cells; mesophyll cells
D)the night; the day

Question 36

All of the following are vascular plants EXCEPT:

A)green algae.
B)ferns/horsetails.
C)angiosperms.
D)gymnosperms.
E)lycophytes.

Question 37

In the spring, you pass by a rocky outcrop that is dripping with water and covered with a carpet of short green plants. In the summer, you notice that water is no longer dripping off the rock, and the plants appear brittle and dry. In the fall, the rock is again wet, and the plants now appear soft and green. These plants are MOST likely to be:

A)angiosperms.
B)gymnosperms.
C)algae.
D)lycophytes.
E)bryophytes.

Question 38

Assuming the stomata are open to the same degree, the rate of transpiration should _____ on a rainy day compared with a sunny day because the H₂O concentration gradient from the inside to the outside of the leaf would _____.

A)decline; decrease
B)decline; increase
C)remain the same; not change
D)increase; decrease
E)increase; increase

Question 39

CAM photosynthesis improves the CO₂/H₂O exchange ratio because:

A)organic acids are decarboxylated at night.
B)organic acids are decarboxylated in daylight.
C)CO₂ capture occurs at night when the gradient for diffusion of H₂O out of the leaf is smaller.
D)CO₂ capture occurs at night when the gradient for diffusion of CO₂ into the leaf is larger.

Question 40

A scientist wants to stop all vascular plants from photosynthesizing. He decides to send his students out to cut off the structures in plants where most photosynthesis takes place. Which structures should his students remove?

A)roots
B)flowers
C)leaves
D)stems

Question 41

Which of the following properties of guard cells allow them to open and close a stoma?

A)radially organized microfibrils
B)tangentially organized microfibrils
C)two guard cells being anchored together at their ends
D)the ability of guard cells to change their ion concentration
E)the lack of cytoplasm in guard cells

Question 42

Where is carbon stored in a CAM plant before its assimilation into sugars?

A)in the vacuole
B)in mesophyll cells
C)in the air spaces between cells
D)in epidermal cells
E)in stomata

Question 43

Where do mesophyll cells usually obtain CO₂ for photosynthesis?

A)from the air spaces that surround them
B)from the xylem
C)from other mesophyll cells
D)from cellular respiration
E)None of the answer options is correct.

Question 44

Which of the following is/are NOT part of the shoot system?

A)leaves
B)stems
C)flowers
D)roots
E)fruits

Question 45

The waxy substance on leaf surfaces is the:

A)cuticle.
B)stomata.
C)epidermis.
D)leaf hair.
E)mesophyll.

Question 46

The structure(s) that allow(s) gasses, such as CO₂, to diffuse into and out of a leaf is/are the:

A)cuticle.
B)stomata.
C)veins.
D)mesophyll cells.
E)vascular bundles.

Question 47

How is C₄ photosynthesis able to achieve higher concentrations of CO₂ in the vicinity of rubisco than photosynthesis in C₃ plants can?

A)by separating carbon capture from carbon fixation
B)by suppressing photorespiration
C)by capturing HCO₃^- instead of CO₂
D)because the C4 cycle is faster than the Calvin cycle

Question 48

Which of the following statements are TRUE of CAM photosynthesis?

A)The Calvin cycle is active during the day.
B)Organic acids are decarboxylated at night.
C)Organic acids are decarboxylated in daylight.
D)CO₂ capture and fixation occur at different times.
E)CO₂ capture and fixation occur in different cells.

Question 49

Recall that C₄ plants tend to have higher rates of photosynthesis when compared with C₃ plants (under normal 21% O₂ atmospheric conditions). If photosynthetic rates are higher, why aren't all plants C₄ plants?

A)Because of the need to regenerate PEP, C₄ photosynthesis consumes more energy than C₃ photosynthesis.
B)Because of rubisco, C₄ photosynthesis consumes more O₂ than C₃ photosynthesis.
C)Because of mesophyll cells, C₄ photosynthesis requires more chlorophyll than C₃ photosynthesis.
D)Because of leaf veins, C₄ photosynthesis requires more H₂O than C₃ photosynthesis.

Question 50

Rubisco's affinity for CO₂ versus O₂ is inversely related to temperature, resulting in _____ as temperatures rise.

A)increased photosynthesis
B)increased photorespiration
C)a slowing rate of enzymatic reaction
D)higher dissolved O₂ levels in the chloroplast

Question 51

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

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 52

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?

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 53

The timing of _____ is a feature that distinguishes CAM and C₄ photosynthesis.

A)stomatal opening
B)carbohydrate production
C)rubisco activity and the Calvin cycle
D)mitochondrial respiration

Question 54

Plants lose several hundred H₂O molecules for each CO₂ that is fixed by photosynthesis because:

A)the concentration gradient is many times larger for H₂O than for CO₂.
B)H₂O molecules are lighter than CO₂ molecules and thus diffuse faster.
C)H₂O molecules are consumed during photosynthesis.
D)the evaporation of so many H₂O molecules is necessary to keep photosynthesis at its optimum temperature.

Question 55

Which of the following cause stomata to close?

A)abscisic acid
B)water loss
C)sunlight
D)low CO₂ in the leaf
E)high leaf temperature

Question 56

Plants have developed BOTH cuticles and crassulacean acid metabolism (CAM) in an attempt to limit which of the following?

A)photorespiration
B)excess photosynthesis
C)PEP carboxylase loss
D)water loss

Question 57

Limits to the capacity of the _____ to store _____ can limit the rate of carbohydrate production in CAM leaves.

A)vacuole; phosphoenol pyruvate
B)vacuole; organic acids
C)leaf; CO₂
D)leaf; HCO₃^-

Question 58

Photorespiration _____ O₂ and _____ CO₂.

A)releases; consumes
B)releases; releases
C)consumes; releases
D)consumes; consumes

Question 59

CAM plants:

A)perform the Calvin cycle at night.
B)store CO₂ in bundle-sheath cells.
C)capture CO₂ at night.
D)specifically avoid photorespiration.
E)All of these choices are correct.

Question 60

Stomata are key sites of information processing because they:

A)respond to CO₂ demand.
B)respond to H₂O loss.
C)open in response to O_2.
D)open in response to light.

Question 61

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

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.

Question 62

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

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 63

You are studying two closely related tree species, one growing in a well-watered environment and one in a drier environment. You find that both species have similar photosynthetic rates and keep their stomata open for the same amount of time over the growing season, yet the species from the drier environment does not grow in height as quickly. A reasonable hypothesis for its slower growth might be that in the drier environment:

A)roots have to respire more to pull water from the soil, reducing the carbohydrate available for growth.
B)it takes more energy to generate enough osmotic pressure to open the guard cells in dry environments.
C)a plant has to invest more in leaf area to generate sufficient evaporative forces to pull water from drier soil.
D)stems and leaves have to invest in stiffer and denser xylem to support the tensions required to pull water from drier soil.

Question 64

Transpiration is BEST defined as the:

A)evaporative loss of water through the stomata.
B)movement of water in the xylem.
C)movement of water from the air into the plant.
D)movement of water into the stomata.
E)evaporative loss of CO₂ through the stomata.

Question 65

Which of the following statements is FALSE regarding CO₂ storage in a CAM plant?

A)CO₂ is stored as a 4-carbon organic acid.
B)CO₂ is stored as a result of the activity of PEP carboxylase.
C)The storage form is converted to CO₂ when sunlight is available.
D)CO₂ storage allows stomata to be open at night.
E)The storage form enters the Calvin cycle as phosphoenol pyruvate.

Question 66

Photorespiration:

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 67

Plants require a great deal of water because water is consumed in the process of photosynthesis.

Question 68

Which of the following statements about transpiration is TRUE?

A)Transpiration is an active process, requiring ATP to pump water from the soil.
B)Transpiration is primarily an adaptation to cool plant leaves.
C)Transpiration sets in motion the movement of water from the roots to the leaves.
D)Transpiration typically involves the loss of CO₂ in addition to water.
E)Plants have no way of controlling water loss to transpiration.

Question 69

C₄ plants are able to reduce photorespiration by creating a high concentration of CO₂ in bundle-sheath cells where the Calvin cycle occurs.

Question 70

From personal experience, you may have noticed that cut flowers placed in a vase with tap water continue to be "alive" for several days. What is the most likely explanation as to why these cut flowers don't immediately wither and die?

A)The tap water in the vase is an excellent source of nitrogen.
B)The plant can still take up water from the vase via an "evaporative pump."
C)Cells in the flower petals continue to perform photosynthesis.
D)Cavitation allows water to continue to be transported through the flower stems.

Question 71

Measurements of the diameter of a plant stem during a long drought show a gradual decrease in diameter over time and then a sudden return to almost its original diameter, even as the drought continues. Which of the following hypotheses is the MOST likely explanation for the increase in stem diameter?

A)Water flow from the soil increased due to the use of ATP to drive the selective uptake of nutrients, leading to water uptake by osmosis.
B)Water flow from the soil increased due to greater stomatal opening.
C)Air entry and cavitation released the tension in the stem xylem.
D)Redistribution of water from the leaves swelled the stem xylem.

Question 72

Which of the following is NOT the correct combination of plant tissue and function in a leaf?

A)epidermis: covering of leaf surface
B)mesophyll: photosynthetic cells
C)veins: vascular tissue
D)epidermis: protection
E)mesophyll: leaf surface

Question 73

Relative to C₃ plants, the rates of photosynthetic production of CAM plants are high because they can store carbon until it is needed.

Question 74

Which of the following is false regarding CAM?

A)It is found in all the major groups of vascular plants.
B)It is found in epiphytes, such as Spanish moss.
C)It is common in all habitats because it allows more energy-efficient carbon uptake.
D)It is common in plants found in desert environments.
E)It requires more ATP than photosynthesis in C₃ plants.

Question 75

Why do leaves have internal air spaces?

A)to allow all the mesophyll cells to evaporate water and thus pull nutrients to them via an evaporatively driven flow
B)because CO₂ diffusion is 10,000 times faster in air than in water
C)to make leaves lighter and less dense
D)because O₂ diffusion is 10,000 times faster in air than in water

Question 76

Which of the following is NOT something that causes guard cells to close?

A)too little water in the leaf
B)too much CO₂ in the leaf
C)presence of abscisic acid
D)too little CO₂ in the leaf

Question 77

Gymnosperms, such as spruces, often dominate high-latitude boreal forests, whereas angiosperms dominate rainforests because tracheids:

A)are less susceptible to freezing-induced cavitation than vessels, but less efficient for moving large volumes of water.
B)do not freeze as easily as vessels, maintaining flow to support photosynthesis at colder temperatures, which is not an advantage in the tropics.
C)mature more quickly than vessels, allowing gymnosperms to make more efficient use of the shorter growing seasons of boreal forests.
D)better withstand the large tensile forces required to extract water from frozen soils than vessels, but offer no advantage in warm tropical soils.

Question 78

What happens to the tension in the xylem when the stomata close and evaporation stops?

A)It goes to zero once evaporation ceases.
B)It remains constant the moment the stomata close.
C)It drops to a value closer to that of the water-filled pores in the soil.
D)It continues to increase until the living cells of the leaf are fully hydrated.

Question 79

Guard cells can actively increase their volume and, therefore, size by:

A)increasing the amount of solutes, such as K⁺ and Cl^-.
B)reducing the amount of solutes, such as K⁺ and Cl^-.
C)increasing the amount of water in the cells without changing solute concentration.
D)decreasing the amount of water in the cells without changing solute concentration.
E)increasing the amount of CO₂ in the cells.

Question 80

What controls the opening and closing of stomata?

A)leaf shape
B)vascular bundles
C)guard cells
D)mesophyll cells
E)Stomata are always open.