chapter 36

_____ cells are the cells that regulate the opening and closing of stomata, thus playing a role in regulating transpiration. a. Guard b. Tracheid c. Casparian strip d. Companion e. Sieve-tube member

a. Guard

Transpiration provides the driving force for the movement of water from the soil to the highest leaves of plants. Transpiration is also linked to other processes in plants, including photosynthesis and the transport of mineral nutrients. Which of the following statements correctly describe(s) a relationship between transpiration and other processes in plants? (MULTIPLE) -- a. Transpiration is important in cooling leaves on warm, sunny days. b. To minimize water loss during dry conditions, most plants must also restrict their ability to carry out photosynthesis. c. Water is pulled from the roots to the leaves by transpiration, whereas mineral nutrients diffuse from the roots to the leaves. d. In most plants, the highest rate of transpiration occurs when the rate of photosynthesis is also highest. e. The large surface area exposed to air inside the leaf maximizes the plant's ability to absorb CO2 while minimizing water loss through transpiration. f. Open stomata provide a low-resistance pathway for CO2 to enter and for water to exit the leaf.

a. Transpiration is important in cooling leaves on warm, sunny days. b. To minimize water loss during dry conditions, most plants must also restrict their ability to carry out photosynthesis. d. In most plants, the highest rate of transpiration occurs when the rate of photosynthesis is also highest. f. Open stomata provide a low-resistance pathway for CO2 to enter and for water to exit the leaf.

Mycorrhizae are... a. mutualistic associations between plant roots and fungi b. structures that promote self-pruning in plants c. a type of leaf found in perennial grasses d. mutualistic associations between plants and nitrogen-fixing bacteria e. structures that minimize water loss from leaves

a. mutualistic associations between plant roots and fungi

Some xerophytes minimize water loss by... a. using the CAM pathway b. developing a Casparian strip between their leaves and stem c. having leaves with a large surface-to-volume ratio d. reducing the thickness of the leaf cuticle

a. using the CAM pathway

True or false? Root pressure can move water a long distance up the xylem because of the higher water potential of the xylem in comparison to the water potential in the surrounding cells. a. True b. False

b. False

True or false? The rate of sugar transport in a plant depends on the rate of photosynthesis, the rate of transpiration, and the difference in turgor pressure between the source and the sink. a. True b. False

b. False

_____ bonds are responsible for the cohesion of water molecules. a. Nonpolar covalent b. Hydrogen c. Polar covalent d. Ionic e. Peptide

b. Hydrogen

Some plant species are used for phytoremediation because when grown in soil contaminated by heavy metals and other pollutants, they accumulate the contaminants in their tissues. In this way, they can be used to clean up the soil. Such plants are called "hyper-accumulators." Other plants, however, cannot take up the contaminants from the soil and are called "non-accumulators." If you were to analyze root cross sections from each of these types of plants after they were grown in contaminated soil, what differences would you likely find? -- a. Hyper-accumulators would have contaminants in the vascular cylinder but not the cortex, and non-accumulators would have contaminants in the cortex but not the vascular cylinder. b. Hyper-accumulators would have contaminants in the cortex and vascular cylinder, and non-accumulators would have contaminants in the cortex but not the vascular cylinder. c. Hyper-accumulators would have contaminants in the vascular cylinder but not the cortex, and non-accumulators would have contaminants in the cortex and the vascular cylinder. d. Hyper-accumulators would have contaminants in the cortex but not the vascular cylinder, and non-accumulators would have contaminants in the vascular cylinder but not the cortex.

b. Hyper-accumulators would have contaminants in the cortex and vascular cylinder, and non-accumulators would have contaminants in the cortex but not the vascular cylinder.

Which of these statements about the Casparian strip is true? a. It is selectively permeable to water. b. It is a waxy band of suberin around cells of the endodermis. c. It is hydrophobic. d. It blocks apoplastic transport into the vascular cylinder. e. It prevents symplastic transport into the vascular cylinder.

b. It is a waxy band of suberin around cells of the endodermis. c. It is hydrophobic. d. It blocks apoplastic transport into the vascular cylinder.

The concentrations of some essential minerals are much higher in the vascular cylinder of roots than in the soil solution around the roots. What is the best explanation for this observation? a. Essential minerals are also needed by other organisms in the soil, depleting the minerals in the soil. b. Some essential minerals are taken into the symplast by active transport. c. Essential minerals are actively transported into the vascular cylinder by the Casparian strip. d. Essential minerals accumulate in the apoplast, reaching higher concentrations than in the soil.

b. Some essential minerals are taken into the symplast by active transport

Which of the following statements about xylem transport is true? a. Water and minerals enter the xylem by diffusion. b. Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves. c. All water transported by the xylem is used for photosynthesis in the leaves. d. The xylem cells that conduct water and minerals are alive.

b. Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves.

Movement of phloem sap from a source to a sink... a. occurs through the apoplast of sieve-tube elements. b. depends ultimately on the activity of proton pumps. c. depends on tension, or negative pressure potential. d. results mainly from diffusion.

b. depends ultimately on the activity of proton pumps.

What forces would be necessary to carry you to the leaves of the trees? (MULTIPLE) a. gravity b. diffusion c. cohesion of water molecules d. turgor pressure e. water potential f. adhesion in the xylem

b. diffusion c. cohesion of water molecules e. water potential f. adhesion in the xylem

A plant cell placed in a solution with a lower (more negative) water potential will... a. lose water and burst b. lose water and plasmolyze c. gain water and plasmolyze d. gain water and become turgid e. lose water and become turgid

b. lose water and plasmolyze

What would enhance water uptake by a plant cell? a. increasing the Ψ of the cytoplasm b. positive pressure on the surrounding solution c. the loss of solutes from the cell d. decreasing the Ψ of the surrounding solution

b. positive pressure on the surrounding solution

Photosynthesis ceases when leaves wilt, mainly because... a. the chlorophyll in wilting leaves is degraded. b. stomata close, preventing CO2CO2 from entering the leaf. c. accumulation of CO2CO2 in the leaf inhibits enzymes. d. photolysis, the water-splitting step of photosynthesis, cannot occur when there is a water deficiency.

b. stomata close, preventing CO2CO2 from entering the leaf.

The proton pump... a. operates by osmosis b. uses the energy stored in ATP to produce a hydrogen ion gradient across membranes. c. releases kinetic energy d. is a passive process e. uses the energy of a proton gradient to generate ATP

b. uses the energy stored in ATP to produce a hydrogen ion gradient across membranes.

What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day? a. Both the photosynthesis and transpiration rates are high. b. The photosynthesis rate is low and stomata are open. c. Both the photosynthesis and transpiration rates are low. d. The photosynthesis rate is high and phloem transport rates are low.

c. Both the photosynthesis and transpiration rates are low.

Root hairs have which of the following roles in absorption and transport of water and minerals? (MULTIPLE) a. Block the flow of soil solution through the apoplast b. Transport soil solution to the vascular cylinder by bulk flow c. Increase surface area of contact between the root epidermis and the soil solution d. Prevent the leakage of accumulated minerals back into the soil e. Absorb the soil solution into the apoplast and symplast

c. Increase surface area of contact between the root epidermis and the soil solution e. Absorb the soil solution into the apoplast and symplast

Which term describes an area where sugars are used or stored? a. Leaves b. Source c. Sink d. Stomata

c. Sink

Which of the following statements about the distribution of sap throughout a plant is true? a. The driving force for sugar movement is transpiration. b. Companion cells form the conducting tissue for sap. c. The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis. d. The main component of phloem sap is glucose.

c. The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis.

The solute most abundant in phloem sap is... a. amino acids b. hormones c. sugar d. minerals e. water

c. sugar

Which one of the following refers to the loss of water through the stomata in a plant's leaves? a. osmosis b. bulk flow c. transpiration d. respiration e. guttation

c. transpiration

Which tissue acts as a filter on the water absorbed by root hairs? a. Epidermis b. Vascular tissue c. Cortex d. Endodermis

d. Endodermis

_____ provide(s) the major force for the movement of water and solutes from roots to leaves. a. Bulk flow b. Translocation c. Transfer cells d. Transpiration e. Root pressure

d. Transpiration

Compared with a cell with few aquaporin proteins in its membrane, a cell containing many aquaporin proteins will... a. have a lower water potential. b. accumulate water by active transport. c. have a higher water potential. d. have a faster rate of osmosis.

d. have a faster rate of osmosis.

Which of the following would tend to increase transpiration? a. spiny leaves b. sunken stomata c. a thicker cuticle d. higher stomatal density

d. higher stomatal density

Which of the following is an adaptation that enhances the uptake of water and minerals by roots? a. active uptake by vessel elements b. pumping through plasmodesmata c. rhythmic contractions by cells in the root cortex d. mycorrhizae

d. mycorrhizae

Which of these are symbiotic associations? a. symplast b. Casparian strips c. root hairs d. mycorrhizae e. apoplasts

d. mycorrhizae

What pathways would be necessary to carry you to the leaves of the trees? a. bulk flow b. symplastic c. apoplastic d. transmembrane e. All of the above.

e. All of the above.

In addition to transporting sugar, the phloem also... a. transmits electrical signals b. transports plant RNA throughout the plant c. transports proteins throughout the plant d. transports viral RNA throughout the plant e. All of the listed responses are correct.

e. All of the listed responses are correct.

In roots the _____ forces water and solutes to pass through the plasma membranes of _____ cells before entering the _____. a. transpiration; endodermis; xylem b. xylem; endodermis; Casparian strip c. Casparian strip; ectoderm; xylem d. Casparian strip; endodermis; phloem e. Casparian strip; endodermis; xylem

e. Casparian strip; endodermis; xylem

Which of the following is a correct statement about a difference between xylem and phloem transport? a. Transpiration moves phloem sap but not xylem sap. b. Xylem sap moves from sugar source to sink, but phloem sap does not. c. Active transport moves xylem sap but not phloem sap. d. Phloem carries water and minerals; xylem carries organic molecules. e. Xylem sap moves up; phloem sap moves up or down.

e. Xylem sap moves up; phloem sap moves up or down.

Plants must always compromise between maximizing __________ and minimizing __________. a. access to light, intake of CO2 b. water loss, proton uptake c. transport of minerals, transport of sugars d. water absorption, leaf area e. photosynthesis, water loss

e. photosynthesis, water loss