Question 1

The graph below shows daily water potential in the xylem of a woody plant. Which of the following statements is best supported using the data?

Accepted Answer

A)  Water potential decreases, beginning around 6 am, because of increased mineral uptake. 
B)  High water potential results in greater transpiration. 
C)  Water potential at noon is a reflection of high rates of transpiration. 
D)  Increasing pressure potential after noon results in decreasing water potential.

Question 2

Long-distance transport in phloem requires which of the following processes?
I. a positive water potential
II. active transport through parenchyma cells
III. cohesion between water molecules
IV. evaporation of water molecules

Accepted Answer

A)  I and II only 
B)  II and III only 
C)  I, II, and III only 
D)  I, II, III, and IV

Question 3

A student examined a leaf and observed that it was dark green, thin, had stoma on the lower surface only, and had a total surface area of more than two square meters. In which environment was the leaf most likely growing?

Accepted Answer

A)  a large, still pond 
B)  a tropical rain forest 
C)  an oasis within a grassland 
D)  the floor of a deciduous forest

Question 4

Which of the following would tend to increase transpiration?

Accepted Answer

A)  spiny leaves 
B)  sunken stomata 
C)  a thicker cuticle 
D)  higher stomatal density

Question 5

Which one of the following statements about the transport of nutrients in phloem is correct?

Accepted Answer

A)  Solute particles are actively transported from phloem at the source. 
B)  Companion cells control the rate and direction of movement of phloem sap. 
C)  Differences in osmotic concentration at the source and sink cause a hydrostatic pressure gradient to be formed. 
D)  A sink is the part of a plant where a particular solute is produced.

Question 6

The value for Ψ in root tissue was found to be -0.15 MPA. Which of the following best describes water flow if the root tissue was placed it in a 0.1 M solution of sucrose (Ψ = -0.23 MPa)?

Accepted Answer

A)  Water would flow from the tissue into the sucrose solution. 
B)  Water would flow from the sucrose solution into the tissue. 
C)  Water would flow in both directions and the concentrations would remain equal. 
D)  Water would flow only if ATP was hydrolyzed in the tissue.

Question 7

Which one of the following played a critical role in water absorption necessary for the successful colonization of land by plants?

Accepted Answer

A)  ground tissue 
B)  bacterial association 
C)  mycorrhizae 
D)  cuticle on leaf surface

Question 8

The leaf area index is described by which of the following ratios?

Accepted Answer

A)  upper leaf surface of a single plant divided by the surface area of the land on which the plant grows 
B)  lower leaf surface of a single plant divided by the total surface area of leaves on the plant 
C)  upper leaf surface of a single plant multiplied by the surface area of the land on which the plant grows 
D)  lower leaf surface of a single plant multiplied by the total surface area of leaves on the plant

Question 9

Which of the following supports the finding that sugar translocation in phloem is an active (energy-requiring) process?

Accepted Answer

A)  Sucrose occurs in higher concentrations in companion cells than in the mesophyll cells where it is produced. 
B)  Movement of water occurs from xylem to phloem and back again. 
C)  Strong pH differences exist between the cytoplasm of the companion cell and the mesophyll cell. 
D)  ATPases are abundant in the plasma membranes of the mesophyll cells.

Question 10

Which of the following terms describes the physical property that predicts the direction of water flow in plants?

Accepted Answer

A)  potassium pump 
B)  water potential 
C)  osmotic potential 
D)  sodium pump

Question 11

Ignoring all other factors, what weather conditions would result in the fastest delivery of water and minerals to the leaves of an oak tree?

Accepted Answer

A)  a cool, dry day 
B)  a warm, dry day 
C)  a warm, humid day 
D)  a cool, humid day

Question 12

Which of the following would be least likely to affect osmosis in plants?

Accepted Answer

A)  a difference in solute concentrations 
B)  receptor proteins in the membrane 
C)  aquaporins 
D)  a difference in water potential

Question 13

Which of following ions play the primary role in basic transport processes in plant cells?

Accepted Answer

A)  H+ 
B)  Na+ 
C)  K+ 
D)  Ca2+

Question 14

Which of the following does not contribute to forming the curved upper surface of water inside a narrow tube such as a tracheid or vessel?

Accepted Answer

A)  the downward pull of gravity on the water column in the tube 
B)  downward pressure from the atmosphere on the topmost layer of water molecules 
C)  the water molecules adjacent to the tube wall being pulled upward by adhesion to the wall 
D)  the topmost layer of water molecules being pulled downward by cohesion to the water molecules below

Question 15

What is the overall charge on the cytoplasmic side of a plant cell plasma membrane?

Accepted Answer

A)  positive 
B)  negative 
C)  neutral 
D)  variable, depending on co-transport

Question 16

What is the advantage of having small, needlelike leaves?

Accepted Answer

A)  increased transpiration rate 
B)  decreased transpiration rate 
C)  increased efficiency of light capture 
D)  decreased efficiency of light capture

Question 17

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?

Accepted Answer

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.

Question 18

The phyllotaxy of mature shoots can be described by a phyllotactic fraction where the numerator indicates the number of times you must go around the stem to get to another leaf directly above (or below) the starting leaf and the denominator indicates the number of leaves passed through to get back in-line with the starting leaf. These two numbers can also be used to calculate the angle between successive leaves. The most common patterns are summarized in the table below.

What is an advantage to plants as the numbers of leaves passed through increase?

Accepted Answer

A)  The shoot apex will get larger as it produces larger numbers of leaves. 
B)  The number of leaves passed through will always increase at a faster rate than the number of times around the stem so there will be more photosynthesis. 
C)  The phyllotactic fraction is random, so a "counting mechanism" is not necessary. 
D)  The angle between leaves approaches 137.5o which minimizes shading of lower leaves by upper leaves.

Question 19

Which of the following experimental procedures would most likely reduce transpiration while allowing the normal growth of a plant?

Accepted Answer

A)  subjecting the leaves of the plant to a partial vacuum 
B)  increasing the level of carbon dioxide around the plant 
C)  putting the plant in drier soil 
D)  decreasing the relative humidity around the plant

Question 20

Which of the following is an adaptation that enhances the uptake of water and minerals by roots?

Accepted Answer

A)  mycorrhizae 
B)  pumping through plasmodesmata 
C)  active uptake by vessel elements 
D)  rhythmic contractions by cells in the root cortex

Exam 36: Transport in Vascular Plants