Deck 37: Transport in Plants

Question 1

On a short-term basis, water loss in plants may be controlled by the

A)bending of the petioles on the leaves.
B)closing of the stele in the roots.
C)closing of the stomata in the leaves to limit transpiration.
D)opening of the stomata in the leaves to allow more carbon dioxide to enter.

Answer 1

C

Question 2

Which of the following statements about transport through phloem is true?

A)Transport only occurs from the roots to the shoot.
B)It is aided by root pressure.
C)The direction of flow can change at different times if the sources and sinks change.
D)No energy is required.

Answer 2

C

Question 3

Which of the following statements does not apply to aquaporins?

A)They are water transport channels.
B)They are unique to plant cells.
C)They occur in the plasma membrane.
D)They speed up osmosis.

Answer 3

B

Question 4

The process by which water is "pulled" up through the xylem columns of plants as it evaporates out of the leaves is called

A)respiration.
B)transpiration.
C)osmosis.
D)anhydration.

Question 5

A plant is exposed to a toxin that blocks ABA receptor sites in the plasma membrane.What is the likely consequence of this exposure?

A)Oxygen deprivation will trigger the release of ethylene, which will in turn suppress root growth.
B)Gibberellin production will increase, allowing the plant to access more nutrients in the soil.
C)ABA will enter the cells by an alternative route and normal function will be restored.
D)The plant will lose excess water through transpiration and suffer dehydration.

Question 6

Which of the following must occur in order to maintain a high pressure potential within guard cells?

A)Potassium ions must be actively transported out.
B)Energy must be constantly expended.
C)Water must exit guard cells by osmosis.
D)Stomata must take up more oxygen and less carbon dioxide.

Question 7

The Calvin Cycle can only produce sugar if ______can enter through the pores of the leaves.

A)O₂
B)CO₂
C)water
D)potassium

Question 8

Water moves through a plant by each of the following methods except

A)from cell to cell through plasmodesmata.
B)through the Casparian strip.
C)through the spaces between cells.
D)through vessel members.

Question 9

Stomatal opening requires each of the following conditions, except

A)expenditure of energy.
B)a reduction of turgor in the guard cells.
C)water entering the guard cells by osmosis.
D)a lower water potential in the guard cells.

Question 10

Turgor is most directly related to the plant cells'

A)total water potential.
B)pressure potential.
C)solute potential.
D)osmosis.

Question 11

Some plants are able to endure frequent flooding events because they contain a tissue with loose parenchyma cells and large air spaces called

A)xylem.
B)spongy mesophyll.
C)pneumatophores.
D)aerenchyma.

Question 12

Mangrove plants live in areas regularly flooded with salt water.Which of these is not a possible mechanism for controlling their salt balance?

A)The roots block salt uptake.
B)The succulent leaves contain large quantities of water that dilute salt that is absorbed.
C)Absorbed salt is secreted from special salt glands.
D)Modified roots emerge above the water level and help oxygen diffuse into the roots.

Question 13

Which of the following actions occurs in many plants when CO₂ concentrations are high?

A)Guard cells lose turgor, and the stomata close.
B)Water evaporates at a higher rate than usual.
C)CAM photosynthesis fixes CO₂ at night.
D)Oxygen is used by plants for photosynthesis.

Question 14

Even in the absence of transpiration, some water can move into the roots and partially up the xylem columns.This phenomenon is due to

A)flooding.
B)stomatal opening.
C)root pressure.
D)proton pumps.

Question 15

Cavitation can occur when what happens?

A)Root pressure pushes water up the xylem.
B)Starch grains block the sieve tubes.
C)Gas bubbles expand inside a tracheid or vessel member.
D)Stomata get stuck closed.

Question 16

Most of the water absorbed by the plant enters through the

A)root apical meristem.
B)root cap.
C)root hairs.
D)stomata.

Question 17

The plasma membranes of root hair cells contain a variety of protein transport channels through which specific ions are transported, even against large concentration gradients, by

A)electron pumps.
B)carbohydrate pumps.
C)water pumps.
D)proton pumps.

Question 18

Plants living in standing water often face which of the following problems?

A)increased CO₂ levels
B)chilling of the roots
C)oxygen deprivation
D)loss of stomata

Question 19

A plant will usually wilt when which component of water potential reaches 0 MPa?

A)solute potential
B)turgor pressure
C)total water potential
D)gravity potential When the pressure potential reaches 0 MPa within a cell, there is no more turgor pressure.This pressure is necessary to keep the cell wall rigid and to keep the plant from wilting.Please refer to section 37.1 for more information.

Question 20

Water is able to cross plant plasma membranes by a combination of

A)osmosis and aquaporins.
B)evaporation and diffusion.
C)root pressure and turgidity.
D)diffusion and phloem.

Question 21

Which of the following hormones increases when plants are flooded?

A)gibberellin
B)auxin
C)ethylene
D)cytokinin

Question 22

Which of the following does not require expenditure of energy?

A)accumulation of ions inside a cell
B)transport against a concentration gradient
C)flow of sucrose and other carbohydrates once inside the sieve tubes
D)the loading and unloading of carbohydrates from the sieve tubes

Question 23

Water molecules can "stick" to certain surfaces by

A)adhesion.
B)cohesion.
C)root pressure.
D)water pressure.

Question 24

Closing the stomata for an extended period of time would lead to an increase in G3P in the mesophyll cells.

Question 25

Halophytes are plants that live in saline soils.The high osmotic potential of the salt solution in the soil creates a very negative water potential.What can halophytes do so that water will flow into the roots?

A)They can close their stomata so that less water is lost through transpiration.
B)They can open all their stomata so that transpiration "pulls" more water into the roots.
C)They can increase the solute concentration in their roots creating a water potential that is more negative than the soil.
D)They can pump ions out of the plant creating a water potential in the roots that is more positive than the soil.

Question 26

Most carbohydrates manufactured in leaves and other photosynthetic parts are transported through the phloem to the rest of the plant by the process of

A)transpiration.
B)translocation.
C)osmosis.
D)receptor-mediated transport.

Question 27

Some plants can tolerate flooding conditions by

A)formation of aerenchyma.
B)opening their lenticels.
C)forming additional adventitious roots.
D)shedding their bark.

Question 28

Which of the following equations represents the total water potential of a plant?

A)s² + p² = w²
B) $\Psi$ _s = $\Psi$ _p + $\Psi$ _w
C) $\Psi$ _p = $\Psi$ _w + $\Psi$ _s
D) $\Psi$ _w = $\Psi$ _p + $\Psi$ _s

Question 29

If the soil around a plant is treated with a fungicide, the plant may experience a decline in DNA synthesis.

Question 30

A large watermelon fruit is very heavy and contains nearly 90% water.Since the skin of a watermelon is thick and lacks stomata, transpiration does not "pull" water into the watermelon.So, how does all that water get into the fruit?

A)Root pressure pushes water into the watermelon.
B)Water enters by osmosis from the soil.
C)Water is pumped in by active transport.
D)Water is transported in the phloem along with the sugars while they are being translocated into the fruit.

Question 31

Cavitation would have no effect on translocation.

Question 32

In Cell 3,

A) $\Psi$ _p = 0.0 MPa and $\Psi$ _w = -0.5 MPa.
B) $\Psi$ _p = 0.0 MPa and $\Psi$ _w = 0.0 MPa.
C) $\Psi$ _p = +0.5 MPa and $\Psi$ _w = -0.5 MPa.
D) $\Psi$ _p = -0.5 MPa and $\Psi$ _w = -0.5 MPa.

Question 33

Pure water without applied pressure has a water potential that is equal to

A)infinity.
B)0.0 MPa.
C)1.6 MPa.
D)-2.0 MPa.

Question 34

Mycorrhizal fungi interact with plants at the

A)stomata.
B)seed coat.
C)roots.
D)edge of ponds.

Question 35

In Cell 1,

A) $\Psi$ _p = 0.0 MPa and $\Psi$ _w = 0.0 MPa.
B) $\Psi$ _p = 0.0 MPa and $\Psi$ _w = -1.0 MPa.
C) $\Psi$ _p = +0.5 MPa and $\Psi$ _w = -0.5 MPa.
D) $\Psi$ _p = -0.5 MPa and $\Psi$ _w = -0.5 MPa.

Question 36

Which of these situations regarding phloem sources and sinks is not correct?

A)The root of a carrot plant is a source.
B)Young leaves are sinks.
C)A growing pumpkin is a sink.
D)In a seedling, the cotyledons would be sources.

Question 37

The pressure-flow hypothesis describes

A)how hormones move through the phloem.
B)how carbohydrates enter the sieve tubes.
C)how carbohydrates in solution move through the phloem.
D)how water and minerals move through the xylem.

Question 38

Water may be lost in the form of liquid from the surface of leaves through a process known as

A)guttation.
B)cohesion.
C)phloem loading.
D)mesophyll adhesion.

Question 39

You a given a plant tissue in lab and asked to determine if the tissue is a source or a sink.Microscopic analysis reveals an abundance of colorless parenchyma cells with plastids.Only one biochemical test reacts positively with your sample.In the presence of iodine, the plastids turn a dark purplish color.Based on this information you determine your sample is

A)a source because your sample is rich in carbohydrates.
B)a source because your sample contains plastids.
C)a sink because your sample is rich in carbohydrates.
D)both a source and sink because it contains both plastids and carbohydrates.

Question 40

The uneven distribution of an impermeable solute on either side of a membrane will result in

A)an increase in oxygen deprivation.
B)proton pumping.
C)root pressure.
D)osmosis.

Question 41

If the proton pumps of guard cell were damaged, transpiration would decrease.

Question 42

If a mutation decreased the radius of a xylem vessel threefold, there would be an 81-fold increase in the volume of liquid moving through the vessel.

Question 43

A decrease in the availability of ATP in a root cell could decrease the water potential of the cell.

Question 44

An application of too much fertilizer will negatively affect the movement of materials in the phloem.

Question 45

An increase in root pressure will result in the rapid release of abscisic acid (ABA) and the subsequent opening of the stomata.