Xylem vessels, found in angiosperms, have a much greater internal diameter than tracheids, the only xylem-conducting cells found in gymnosperms. The tallest living trees, redwoods, are gymnosperms. Which of the following is an advantage of tracheids over vessels for long-distance transport to great heights?

Xylem vessels, found in angiosperms, have a much greater internal diameter than tracheids, the only xylem-conducting cells found in gymnosperms. The tallest living trees, redwoods, are gymnosperms. Which of the following is an advantage of tracheids over vessels for long-distance transport to great heights? 

A) Adhesive forces are proportionally greater in narrower cylinders than in wider cylinders.
B) The smaller the diameter of the xylem, the more likely cavitation will occur.
C) Cohesive forces are greater in narrow tubes than in wide tubes of the same height.
D) Adhesive forces are proportionally greater in narrower cylinders than in wider cylinders, and cohesive forces are greater in narrow tubes than in wide tubes of the same height.
E) Adhesive forces are proportionally greater in narrower cylinders than in wider cylinders, and the smaller the diameter of the xylem, the more likely cavitation will occur.







Answer: D

Which of the following statements is false concerning the xylem?

Which of the following statements is false concerning the xylem? 

A) Xylem tracheids and vessels fulfill their vital function only after their death.
B) The cell walls of the tracheids are greatly strengthened with cellulose fibrils forming thickened rings or spirals.
C) Water molecules are transpired from the cells of the leaves, and replaced by water molecules in the xylem pulled up from the roots due to the cohesion of water molecules.
D) Movement of materials is by mass flow; solutes in xylary sap move due to a positive turgor pressure gradient from source to sink.
E) In the morning, sap in the xylem begins to move first in the twigs of the upper portion of the tree, and later in the lower trunk.






Answer: D

Active transport would be least important in the normal functioning of which of the following plant tissue types?

Active transport would be least important in the normal functioning of which of the following plant tissue types? 

A) leaf transfer cells
B) stem tracheary elements
C) root endodermal cells
D) leaf mesophyll cells
E) root sieve-tube elements






Answer: B

Which of the following statements about transport in plants is false?

Which of the following statements about transport in plants is false? 

A) Weak bonding between water molecules and the walls of xylem vessels or tracheids helps support the columns of water in the xylem.
B) Hydrogen bonding between water molecules, which results in the high cohesion of the water, is essential for the rise of water in tall trees.
C) Although some angiosperm plants develop considerable root pressure, this is not sufficient to raise water to the tops of tall trees.
D) Most plant physiologists now agree that the pull from the top of the plant resulting from transpiration is sufficient, when combined with the cohesion of water, to explain the rise of water in the xylem in even the tallest trees.
E) Gymnosperms can sometimes develop especially high root pressure, which may account for the rise of water in tall pine trees without transpiration pull.





Answer: E

Transpiration in plants requires all of the following except

Transpiration in plants requires all of the following except 

A) adhesion of water molecules to cellulose.
B) cohesion between water molecules.
C) evaporation of water molecules.
D) active transport through xylem cells.
E) transport through tracheids.






Answer: D

Which of the following is responsible for the cohesion of water molecules?

Which of the following is responsible for the cohesion of water molecules? 

A) hydrogen bonds between the oxygen atoms of a water molecule and cellulose in a vessel cell
B) covalent bonds between the hydrogen atoms of two adjacent water molecules
C) hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule
D) covalent bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule
E) low concentrations of charged solutes in the fluid








Answer: C

Which of the following has the lowest (most negative) water potential?

Which of the following has the lowest (most negative) water potential? 

A) root cortical cells
B) root xylem
C) trunk xylem
D) leaf cell walls
E) leaf air spaces







Answer: E

Water potential is generally most negative in which of the following parts of a plant?

Water potential is generally most negative in which of the following parts of a plant? 

A) mesophyll cells of the leaf
B) xylem vessels in leaves
C) xylem vessels in roots
D) cells of the root cortex
E) root hairs






Answer: A

In which plant cell or tissue would the pressure component of water potential most often be negative?

In which plant cell or tissue would the pressure component of water potential most often be negative? 

A) leaf mesophyll cell
B) stem xylem
C) stem phloem
D) root cortex cell
E) root epidermis






Answer: B

What is the main force by which most of the water within xylem vessels moves toward the top of a tree?

What is the main force by which most of the water within xylem vessels moves toward the top of a tree? 

A) active transport of ions into the stele
B) atmospheric pressure on roots
C) evaporation of water through stoma
D) the force of root pressure
E) osmosis in the root






Answer: C

What drives the flow of water through the xylem?

What drives the flow of water through the xylem? 

A) passive transport by the endodermis
B) the number of companion cells in the phloem
C) the evaporation of water from the leaves
D) active transport by sieve-tube elements
E) active transport by tracheid and vessel elements







Answer: C

If isolated plant cells with a water potential averaging -0.5 MPa are placed into a solution with a water potential of -0.3 MPa, which of the following would be the most likely outcome?

If isolated plant cells with a water potential averaging -0.5 MPa are placed into a solution with a water potential of -0.3 MPa, which of the following would be the most likely outcome? 

A) The pressure potential of the cells would increase.
B) Water would move out of the cells.
C) The cell walls would rupture, killing the cells.
D) Solutes would move out of the cells.
E) The osmotic pressure of the cells would decrease.






Answer: A

One would expect to find the highest density of aquaporins in which of the following?

One would expect to find the highest density of aquaporins in which of the following? 

A) the plasma membrane of guard cells
B) the pits of a tracheid
C) the plasma membrane of parenchyma cells in a ripe fruit
D) the plasma membrane of a mature mesophyll cell in a leaf
E) the membrane lining plasmodesmata






Answer: A

One is most likely to see guttation in small plants when the

One is most likely to see guttation in small plants when the 

A) transpiration rates are high.
B) root pressure exceeds transpiration pull.
C) preceding evening was hot, windy, and dry.
D) water potential in the stele of the root is high.
E) roots are not absorbing minerals from the soil.





Answer: B

The following factors may sometimes play a role in the movement of sap through xylem. Which one depends on the direct expenditure of ATP by the plant?

The following factors may sometimes play a role in the movement of sap through xylem. Which one depends on the direct expenditure of ATP by the plant? 

A) capillarity of water within the xylem
B) evaporation of water from leaves
C) cohesion among water molecules
D) concentration of ions in the symplast
E) bulk flow of water in the root apoplast





Answer: D

Pine seedlings grown in sterile potting soil grow much slower than seedlings grown in soil from the area where the seeds were collected. This is most likely because

Pine seedlings grown in sterile potting soil grow much slower than seedlings grown in soil from the area where the seeds were collected. This is most likely because 

A) the sterilization process kills the root hairs as they emerge from the seedling.
B) the normal symbiotic fungi are not present in the sterilized soil.
C) sterilization removes essential nutrients from the soil.
D) water and mineral uptake is faster when mycorrhizae are present.
E) B and D.





Answer: E

Which of the following is not an important component of the long-distance transport process in plants?

Which of the following is not an important component of the long-distance transport process in plants? 

A) the cohesion of water molecules
B) a negative water potential
C) the root parenchyma
D) the active transport of solutes
E) bulk flow from source to sink





Answer: C

In plant roots, the Casparian strip is correctly described by which of the following?

In plant roots, the Casparian strip is correctly described by which of the following? 

A) It aids in the uptake of nutrients.
B) It provides energy for the active transport of minerals into the stele from the cortex.
C) It ensures that all minerals are absorbed from the soil in equal amounts.
D) It ensures that all water and dissolved substances must pass through a cell membrane before entering the stele.
E) It provides increased surface area for the absorption of mineral nutrients.






Answer: D

What is the role of proton pumps in root hair cells?

What is the role of proton pumps in root hair cells? 

A) establish ATP gradients
B) maintain the H+ gradient
C) pressurize xylem transport
D) eliminate excess electrons
E) assist in active uptake of water molecules






Answer: B

Which of the following statements about xylem is incorrect?

Which of the following statements about xylem is incorrect? 

A) It conducts material from root tips to leaves.
B) The conducting cells are part of the apoplast.
C) It transports mainly sugars and amino acids.
D) It typically has a lower water potential than is found in soil.
E) No energy input is required for transport.






Answer: C