Question 1

Which of the following cross-membrane transport mechanisms occur without expenditure of energy?

Accepted Answer

A) facilitated diffusion 
B) antiporter 
C) symporter 
D) cotransporter 
E) pump 
A) facilitated diffusion 
B) antiporter 
C) symporter 
D) cotransporter 
E) pump A

Question 2

Which of the following is not a net sink for products of photosynthesis in a deciduous angiosperm tree?

Accepted Answer

A) leaves in early spring 
B) flowers in summer 
C) fruits in summer 
D) roots in early spring 
E) roots in early autumn 
A) leaves in early spring 
B) flowers in summer 
C) fruits in summer 
D) roots in early spring 
E) roots in early autumn D

Question 3

Irrigation reduces soil quality and rains usually don't.Why?

Accepted Answer

A) Rains deliver less water to soil than irrigation does. 
B) Water used for irrigation contains fertilizer and pesticides that affect soil quality. 
C) Rainwater contains less inorganic material. 
D) The fast water flow during irrigation removes organic material from soil. 
E) The fast water flow during rains is able to remove toxic materials from topsoil. 
A) Rains deliver less water to soil than irrigation does. 
B) Water used for irrigation contains fertilizer and pesticides that affect soil quality. 
C) Rainwater contains less inorganic material. 
D) The fast water flow during irrigation removes organic material from soil. 
E) The fast water flow during rains is able to remove toxic materials from topsoil. C

Question 4

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) H⁺-ATPases are abundant in the plasma membranes of the mesophyll cells. 
E) All of the above apply. 
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) H⁺-ATPases are abundant in the plasma membranes of the mesophyll cells. 
E) All of the above apply.

Question 5

Water potential of plants during night is ________ compared to day water potential due to ________.

Accepted Answer

A) increased;open stomata 
B) increased;closed stomata 
C) decreased;open stomata 
D) decreased;closed stomata 
A) increased;open stomata 
B) increased;closed stomata 
C) decreased;open stomata 
D) decreased;closed stomata

Question 6

As an undergraduate research assistant in the lab of the famous Dr.S.Nameerf,your duties involve measuring water potential in experimental soil-plant-atmosphere systems.Assume you make a series of measurements in a system under normal daylight conditions,with stomata open and photosynthesis occurring.Which of the following correctly depicts the trend your measurement data should follow if the cohesion-tension mechanism is operating?

Accepted Answer

A) ψsoil < ψroots = ψleaves < ψatmosphere 
B) ψatmosphere < ψleaves = ψroots < ψsoil 
C) ψsoil < ψroots < ψleaves < ψatmosphere 
D) ψatmosphere < ψleaves < ψroots < ψsoil 
A) ψsoil < ψroots = ψleaves < ψatmosphere 
B) ψatmosphere < ψleaves = ψroots < ψsoil 
C) ψsoil < ψroots < ψleaves < ψatmosphere 
D) ψatmosphere < ψleaves < ψroots < ψsoil

Question 7

J.A.Milburn and R.P.C.Johnson developed an acoustic method for detecting cavitation in plants.This involves "listening" for characteristic clicks produced during air-bubble formation,using sensitive microphones and amplifiers.In one experiment with the castor bean plant (Ricinus communis),they detached leaves by cutting the petioles and subjected them to various treatments.Which of the following would be least likely to be observed in such an experiment?

Accepted Answer

A) as the leaf is allowed to wilt,recording many clicks that approximately equal the estimated number of vessels in the cut petiole 
B) after increasing transpiration by blowing warm air across the leaf,recording an increased rate of clicking 
C) after adding water to the cut end of the petiole,recording an increased rate of clicking 
A) as the leaf is allowed to wilt,recording many clicks that approximately equal the estimated number of vessels in the cut petiole 
B) after increasing transpiration by blowing warm air across the leaf,recording an increased rate of clicking 
C) after adding water to the cut end of the petiole,recording an increased rate of clicking

Question 8

Which theory of water transport in xylem can also be used to explain the movement of water in nonvascular plants such as mosses?

Accepted Answer

A) cohesion-tension 
B) capillarity 
C) proton pump 
D) pressure flow 
E) root pressure 
A) cohesion-tension 
B) capillarity 
C) proton pump 
D) pressure flow 
E) root pressure

Question 9

Researchers using a dendrograph found that the trunk diameter of a beech tree increased and decreased slightly on a daily basis and that this variation correlated negatively with transpiration rate.Under which of the following sets of conditions should the daily changes in trunk diameter be the smallest?

Accepted Answer

A) cool spring day,no wind,high soil moisture 
B) cool spring day,no wind,soil partially frozen 
C) hot summer day,windy,low soil moisture 
D) hot summer day,no wind,low soil moisture 
E) hot summer day,windy,high soil moisture 
A) cool spring day,no wind,high soil moisture 
B) cool spring day,no wind,soil partially frozen 
C) hot summer day,windy,low soil moisture 
D) hot summer day,no wind,low soil moisture 
E) hot summer day,windy,high soil moisture

Question 10

CAM and C₄ plants conduct photosynthesis in ways that allow them to live in drier areas than most C₃ plants can tolerate.The effectiveness of different plants in restricting water loss while still allowing for influx of adequate CO₂ can be compared using the transpiration ratio,which is calculated by dividing the amount of water transpired by the amount of CO₂ fixed by photosynthesis.If a typical transpiration ratio for a C₃ plant is 500,then possible values for CAM and C₄ plants could be

Accepted Answer

A) 750-1000. 
B) 500. 
C) 50-250. 
A) 750-1000. 
B) 500. 
C) 50-250.

Question 11

Which of the following would be expected to contribute to relatively high rates of transpiration?

Accepted Answer

A) heavy cloud cover 
B) cool air temperature 
C) calm air 
D) low atmospheric CO₂ concentration 
E) low soil moisture 
A) heavy cloud cover 
B) cool air temperature 
C) calm air 
D) low atmospheric CO₂ concentration 
E) low soil moisture

Question 12

Water potential in plants consists mainly of

Accepted Answer

A) solute potential and osmotic potential. 
B) solute potential and membrane potential. 
C) pressure potential and solute potential. 
D) pressure potential and membrane potential. 
E) solute potential only. 
A) solute potential and osmotic potential. 
B) solute potential and membrane potential. 
C) pressure potential and solute potential. 
D) pressure potential and membrane potential. 
E) solute potential only.

Question 13

Compared to plants from other environments,the cells of many desert plants contain high concentrations of solutes.This helps them survive in their arid surroundings because the high solute concentrations create relatively ________,which help reduce water loss.

Accepted Answer

A) low solute potentials 
B) high pressure potentials 
C) low pressure potentials 
D) high solute potentials 
A) low solute potentials 
B) high pressure potentials 
C) low pressure potentials 
D) high solute potentials

Question 14

Which of the following would not be expected to contribute to high rates of transpiration?

Accepted Answer

A) high atmospheric CO₂ concentration 
B) bright sunlight 
C) warm air temperature 
D) brisk wind 
E) high soil moisture 
A) high atmospheric CO₂ concentration 
B) bright sunlight 
C) warm air temperature 
D) brisk wind 
E) high soil moisture

Question 15

Root pressure can result in the early morning appearance of water droplets on leaves and flowers of low-growing plants.Which of the following does not contribute to the development of root pressure?

Accepted Answer

A) creation of tension in the xylem water column that leads to short-distance water movement 
B) closed stomata 
C) accumulation of ions from the soil by root epidermal cells 
D) movement of ions from epidermis to xylem 
E) creation of a water potential gradient between the xylem (lower ψ)and surrounding cells (higher ψ)in the root 
A) creation of tension in the xylem water column that leads to short-distance water movement 
B) closed stomata 
C) accumulation of ions from the soil by root epidermal cells 
D) movement of ions from epidermis to xylem 
E) creation of a water potential gradient between the xylem (lower ψ)and surrounding cells (higher ψ)in the root

Question 16

Cell-to-cell water movement always occurs from

Accepted Answer

A) higher to lower pressure potential. 
B) higher to lower solute potential. 
C) lower to higher solute potential. 
D) higher to lower water potential. 
E) lower to higher water potential. 
A) higher to lower pressure potential. 
B) higher to lower solute potential. 
C) lower to higher solute potential. 
D) higher to lower water potential. 
E) lower to higher water potential.

Question 17

Which of the following observations provides the strongest evidence against root pressure being the principal mechanism of water transport in the xylem?

Accepted Answer

A) Not all plants have roots. 
B) Not all soils have high concentrations of ions. 
C) It requires movement of water into the xylem from surrounding cells in the roots. 
D) Over long distances,the force of root pressure is not enough to overcome the force of gravity. 
E) It requires development of a water potential gradient between roots and shoots. 
A) Not all plants have roots. 
B) Not all soils have high concentrations of ions. 
C) It requires movement of water into the xylem from surrounding cells in the roots. 
D) Over long distances,the force of root pressure is not enough to overcome the force of gravity. 
E) It requires development of a water potential gradient between roots and shoots.

Question 18

The processes of water flow in xylem and sugar translocation in phloem differ in many respects.Which of the following is not a difference between xylem and phloem transport?

Accepted Answer

A) Water potential gradients are required for xylem transport to occur,but not for phloem transport. 
B) Xylem transport is a wholly passive process;phloem transport includes active (energy-requiring)processes. 
C) Cells through which xylem transport occurs are "dead" at maturity;those in phloem transport are "alive." 
D) Xylem transport always occurs in the same direction;phloem transport does not. 
A) Water potential gradients are required for xylem transport to occur,but not for phloem transport. 
B) Xylem transport is a wholly passive process;phloem transport includes active (energy-requiring)processes. 
C) Cells through which xylem transport occurs are "dead" at maturity;those in phloem transport are "alive." 
D) Xylem transport always occurs in the same direction;phloem transport does not.

Question 19

Formation of menisci,such as occurs in a tube filled with water,is an important factor in plant water movement.A meniscus is created by

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 along the walls of the tube being pulled upward by adhesion. 
D) the topmost layer of water molecules being pulled downward by the water molecules below. 
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 along the walls of the tube being pulled upward by adhesion. 
D) the topmost layer of water molecules being pulled downward by the water molecules below.

Question 20

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis,the volume of the cell increases until it bursts.This does not happen to plant cells,because

Accepted Answer

A) they have large central vacuoles,which provide abundant space for storage of incoming water. 
B) the composition of their plasma membranes differs from that of animal-cell plasma membranes in a way that provides much greater strength. 
C) they have cell walls,which prevent the entry of water by osmosis. 
D) they have cell walls,which provide pressure to counteract the pressure of the incoming water. 
E) certain proteins embedded in their plasma membranes act as "check valves," releasing excess water before it can cause the cell to burst. 
A) they have large central vacuoles,which provide abundant space for storage of incoming water. 
B) the composition of their plasma membranes differs from that of animal-cell plasma membranes in a way that provides much greater strength. 
C) they have cell walls,which prevent the entry of water by osmosis. 
D) they have cell walls,which provide pressure to counteract the pressure of the incoming water. 
E) certain proteins embedded in their plasma membranes act as "check valves," releasing excess water before it can cause the cell to burst.

Exam 37: Water and Sugar Transport in Plants

Which of the following cross-membrane transport mechanisms occur without expenditure of energy?

Which of the following is not a net sink for products of photosynthesis in a deciduous angiosperm tree?

Irrigation reduces soil quality and rains usually don't.Why?

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

Water potential of plants during night is ________ compared to day water potential due to ________.

Which theory of water transport in xylem can also be used to explain the movement of water in nonvascular plants such as mosses?

Which of the following would be expected to contribute to relatively high rates of transpiration?

Water potential in plants consists mainly of

Compared to plants from other environments,the cells of many desert plants contain high concentrations of solutes.This helps them survive in their arid surroundings because the high solute concentrations create relatively ________,which help reduce water loss.

Which of the following would not be expected to contribute to high rates of transpiration?

Root pressure can result in the early morning appearance of water droplets on leaves and flowers of low-growing plants.Which of the following does not contribute to the development of root pressure?

Cell-to-cell water movement always occurs from

Which of the following observations provides the strongest evidence against root pressure being the principal mechanism of water transport in the xylem?

The processes of water flow in xylem and sugar translocation in phloem differ in many respects.Which of the following is not a difference between xylem and phloem transport?

Formation of menisci,such as occurs in a tube filled with water,is an important factor in plant water movement.A meniscus is created by

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis,the volume of the cell increases until it bursts.This does not happen to plant cells,because

Biology and the Tree of Life

Water and Carbon: the Chemical Basis of Life

Protein Structure and Function

Nucleic Acids and the Rna World

An Introduction to Carbohydrates

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