Chapter 35 : Water and Sugar Transport - Homework Questions

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

A

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

C

Chapter 35 : Water and Sugar Transport - Homework Questions

Chapter 35 : Water and Sugar Transport - Homework Questions

According to the pressure-flow hypothesis, what mechanism causes the movement of phloem sap from sources to sink tissues? a.) Pressure potential differences between source and sink b.) Root pressure c.) Transpirational pull from the leaves d.) Solute potential differences between source and sink

A

What is the role of companion cells in the movement of sugars through plants? a.) They accumulate sucrose, which is then transferred to adjacent sieve-tube elements. b.) They are the sites of sugar production by photosynthesis. c.) They are the sites where starch is converted to sucrose. d.) They secrete sucrose, which draws sugars through phloem under negative pressure.

A

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

A

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

B; A sink is an area where sugars are used or stored; typically, these are the roots and fruits of a plant.

The transport of a water column up a very tall tree can be explained by _____. a.) root pressure that pushes water up b.) cohesive and adhesive forces of the water column under evaporative tension c.) positive pressure in xylem that pushes water up d.) gravitational pull

B; The pull of evaporation, combined with the cohesive tendency of water to form hydrogen bonds, moves water.

A mutant plant lacking the ability to pump protons out of leaf companion cells will be unable to do which of the following? a.) initiate transpiration b.) transport water through the xylem c.) load sucrose into sieve cells d.) carry out photosynthesis

C

When water moves from soil into the vascular tissues inside the root, it can take three possible pathways. Of these, the apoplastic route is _____. a.) through aquaporins on the plasma membrane b.) by active diffusion across the plasma membrane c.) between cells and through cell walls d.) through plasmodesmata

C

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

D

Why is the transport of phloem sap considered an active process? a.) Transpiration is driven by the energy in sunlight. b.) Phloem sap is able to move down through a plant with the force of gravity. c.) The manufacture of sucrose via photosynthesis is driven by the energy in sunlight. d.) Energy is used to transport sucrose into companion cells near sources, against a concentration gradient.

D

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.) The photosynthesis rate is high and phloem transport rates are low. d.) Both the photosynthesis and transpiration rates are low.

D; On a cloudy day with low soil moisture, the photosynthesis rate is low and stomata are closed, so the transpiration rate is low.

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

E

Some plants growing in arid climates have small leaves and thick waxy cuticles on the upper epidermis. This is an adaptation for _____. a.) decreasing water loss from leaves b.) increasing water absorption c.) decreasing water breakdown in photosynthesis d.) increasing transpiration

A; Plants in arid climates may also have stomata only on their lower leaf epidermis. The stomata may be in pits, protected from water loss by hairlike epidermal extensions called trichomes.

A cell is placed in a solution that is hypotonic to the cell. Which of the following best describes movement of water in this situation? a.) Water will only flow into the cell. b.) Water will flow into and out of the cell, but the overall net movement will be into the cell. c.) Water will flow into and out of the cell, but the overall net movement will be out of the cell. d.) Water will only flow out of the cell.

B

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

B

Which of the following plant organs may act as a source for translocation of sugars inside a plant? a.) Any non-green tissue b.) Mature leaves c.) Developing flowers d.) Young growing leaves

B

Your friend claims that phloem always carries sugars down a plant. What, if anything, is wrong with that statement? a.) Phloem can carry sugars down a plant, but it can also carry sugars to the left or to the right from its location (e.g. sugars can move to leaves). b.) The statement is completely true. Phloem is responsible for carrying sugars down a plant while xylem carries them up. c.) Phloem can carry sugars down a plant, but it can carry sugars up as well (e.g., if sugars are moving to flowers or fruits).

C

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.

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.

False

The water potential of phloem sap is lowest in which of the following situations? a.) Near leaves at the start of spring b.) Near roots in winter c.) Near leaves in midsummer d.) Near roots at the start of spring

A; The water potential of phloem sap is lowest here because developing leaves are using sucrose faster than they are creating it.

(Refer to table 35.2) The channels indicated by the pointer, are _____. a.) plasmodesmata b.) tight junctions c.) gap junctions d.) mycorrhizae e.) desmosomes

A; Water and ions can pass from cell to cell via these channels. Also, recall that plasmodesmata are a type of cell junction.

(Refer to table 35.1) What would happen if this cell were moved from pure water to a seawater solution? a.) Water would not move in or out of the cell. b.) Water would move in and out of the cell at the same rate. c.) Water would move out of the cell. d.) Water would move into the cell.

C; Because the solute potential would be lower outside the cell, water would move in that direction.

According to the pressure-flow hypothesis, which direction are sucrose and water flowing in the phloem when roots are sources and leaves are sinks? a.) Water flows up the stem and sucrose flows down the stem. b.) Water flows down the stem, and sucrose flows up the stem. c.) Water and sucrose flow down the stem. d.) Water and sucrose flow up the stem.

D

What important role does the Casparian strip play in the movement of water through plants? a.) loads sugars into xylem, thereby causing water to enter the xylem by osmosis b.) acts as a filter that prevents salts, heavy metals, and other pollutants from entering root hairs c.) causes cells to shrink, thereby increasing pressure within cells d.) forces water to move through the cytoplasm of living endodermal cells as it makes its way from the soil to the xylem

D

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

E; Hydrogen bonds among water molecules are responsible for the tendency of those molecules to stick together.

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

E; Transpiration, the evaporation of water from leaves, exerts a pull that bears the primary responsibility for the movement of water and solutes from roots to leaves.