Chapter 3

Question 1

For every gram of organic matter
made by the plant, approximately ____of water is absorbed by the roots

Answer 1

500 g

Question 2

Cell walls allow plant cells
to build up large internal hydrostatic pressures, called ___, which are a result of
their normal water balance

Answer 2

turgor pressure

Question 3

cytoplasm makes up only ____ of the cell volume;

Answer 3

5 to 10%

Question 4

Water typically constitutes ____ of the mass of growing plant tissues.

Answer 4

80 to 95%

Question 5

____is the most abundant and arguably the best solvent known.

Answer 5

Water

Question 6

water As a solvent, makes up the ____for the movement of molecules within
and between cells and greatly influences the ___of proteins, nucleic
acids, polysaccharides, and other cell constituents.

Answer 6

medium; structure

Question 7

___forms the environment in which most of the biochemical reactions of
the cell occur, and it directly participates in many essential chemical reactions

Answer 7

Water

Question 8

Most of the water lost by the plant evaporates from the leaf as the___needed
for photosynthesis is absorbed from the atmosphere.

Answer 8

CO2

Question 9

On a warm, dry, sunny day a leaf will exchange up to ___ of its water in a
single ___.

Answer 9

100%; hour

Question 10

During the plant’s lifetime, water equivalent to ___ times the fresh weight of
the plant may be lost through the leaf surfaces.

Answer 10

100

Question 11

Such water loss in plants is called ___

Answer 11

transpiration

Question 12

is an important means of dissipating the heat input from sunlight

Answer 12

Transpiration

Question 13

Heat dissipates because the water molecules that escape into the atmosphere
have ____, which breaks the __holding them in the
liquid.

Answer 13

higher than-average energy; bonds

Question 14

When these molecules escape, they leave behind a mass of molecules with
___and thus a cooler body of water.

Answer 14

lower-than-average energy

Question 15

For a typical leaf, nearly half of the ____ from sunlight is dissipated
by ___

Answer 15

net heat input; transpiration

Question 16

Of all the resources that plants need to grow and function, ___is the most abundant
and at the same time the most limiting for __

Answer 16

water; agricultural productivity

Question 17

Properties of Water (5)

Answer 17

A. The Polarity of Water Molecules Gives Rise to Hydrogen Bonds

B. The Polarity of Water Makes It an Excellent Solvent

C. The Thermal Properties of Water Result from Hydrogen Bonding

D. The Cohesive and Adhesive Properties of Water Are Due to Hydrogen Bonding

E. Water Has a High Tensile Strength

Question 18

Water has special properties that enable it to act as a solvent and to be readily
transported through the body of the plant. These properties derive primarily from the ___of the water molecule.

Answer 18

polar structure

Question 19

The two intramolecular hydrogen–oxygen bonds
form an angle of ___

Answer 19

105°

Question 20

The opposite partial charges (δ– and δ+) on the water molecule lead to
the formation of ____with other water molecules.

Answer 20

intermolecular hydrogen bonds

Question 21

Oxygen has __
electrons in the outer orbitals; each hydrogen has __.

Answer 21

six ; one

Question 22

The water molecule consists of an oxygen atom ___bonded to __hydrogen
atoms.

Answer 22

covalently ; two

Question 23

Because the oxygen atom is more ___than hydrogen, it tends to attract the ___of the ___bond

Answer 23

electronegative; electrons; covalent

Question 24

– the weak electrostatic attraction between molecules; responsible
for many of the unusual properties of water.

Answer 24

Hydrogen Bond

Question 25

The water's versatility as a solvent is due in part to the ____ of the water molecule and in part to its ___nature

Answer 25

small size; polar

Question 26

the ____ of water makes it a particularly good solvent for ___ substances and for molecules such as sugars and proteins that contain polar ___ or ___groups.

Answer 26

polar nature; ionic; —OH or —NH2

Question 27

extensive ___bonding between water molecules results in unusual ___ properties, such as (2)

Answer 27

hydrogen; thermal; high specific heat and high latent heat of vaporization

Question 28

- the heat energy required to raise the temperature of a substance by a specific amount.

Answer 28

Specific heat

Question 29

___ – the energy needed to separate molecules from the liquid phase and move them into the gas phase at constant ____ – a process that occurs during ___[important component of temperature regulation in plants].

Answer 29

Latent heat of vaporization; temperature; transpiration

Question 30

The _____of water enables plants to cool themselves by ____ water from leaf surfaces, which are prone to heat up because of the radiant input from the sun.

Answer 30

high latent heat of vaporization; evaporating

Question 31

Water molecules at an ____ are more strongly attracted to neighboring water molecules than to the ____ in contact with the water surface.

Answer 31

air–water interface; gas phase

Question 32

an air–water interface minimizes its _____as a consequence of such unequal attraction.

Answer 32

surface area

Question 33

To increase the area of an air–water interface, ___bonds must be broken, which requires an input of ___

Answer 33

hydrogen; energy

Question 34

- the energy required to increase the surface area

Answer 34

Surface tension

Question 35

not only influences the shape of the surface but also may create a pressure in the rest of the liquid.

Answer 35

Surface tension

Question 36

____at the evaporative surfaces of leaves generates the ___that pull water through the plant’s ____

Answer 36

Surface tension; physical forces; vascular system

Question 37

– the mutual attraction between molecules.

Answer 37

Cohesion

Question 38

– attraction of water to a solid phase such as cell wall or glass surface.

Answer 38

Adhesion

Question 39

– movement of water along a capillary tube; result of cohesion, adhesion and surface tension.

Answer 39

Capillarity

Question 40

Cohesion gives water a high ____, defined as the maximum force per unit area that a continuous column of water can withstand before breaking.

Answer 40

tensile strength

Question 41

____ – unit of measurement of pressure [more convenient is ____ which is approximately ___ atmospheres

Answer 41

pascals (Pa); megapascals (MPa); 9.9

Question 42

Water is a constituent of ____

Answer 42

protoplasm

Question 43

Water forms over ___ of the plant body by green or fresh weight basis

Answer 43

90%

Question 44

Plants can synthesis food through photosynthesis only in the presence of ___in their system.

Answer 44

water

Question 45

Water helps to maintain the ___ of cell walls. Water helps in cell ___ due to _____ and _____ which ultimately increase the growth of plant

Answer 45

turgidity; enlargement; turgor pressure; cell division

Question 46

Water is essential in ___process in the plant. It helps in the conversion of ____.

Answer 46

hydraulic; starch to sugar

Question 47

When water moves from the soil through the plant to the atmosphere, it travels through a widely variable medium (4), and the mechanisms of _____ also vary with the type of medium

Answer 47

cell wall, cytoplasm, membrane, air spaces; water transport

Question 48

– integral membrane proteins that form water-selective channels across the membrane

Answer 48

Aquaporins

Question 49

; Because water diffuses faster through such channels than through a lipid bilayer, ___facilitate water movement into plant cells

Answer 49

aquaporins

Question 50

Water molecules in a solution are not ___; they are in continuous motion, colliding with one another and exchanging ___

Answer 50

static; kinetic energy.

Question 51

molecules intermingle as a result of their random __

Answer 51

thermal agitation

Question 52

random motion is called ___. As long as other forces are not acting on the molecules, ___causes the net movement of molecules from regions of high concentration to regions of low concentration—that is, down a ___

Answer 52

diffusion; diffusion; concentration gradient

Question 53

___ (1880s) – German scientist discovered that the rate of diffusion is ___proportional to the concentration gradient.

Answer 53

Adolf Fick; directly

Question 54

Thermal motion of molecules leads to ____—the gradual mixing of molecule and eventual dissipation of concentration differences.

Answer 54

diffusion

Question 55

– rate of transport; amount of substance crossing a unit area per unit time.

Answer 55

Flux density (Js)

Question 56

Diffusion is fastest in ___, slower in __, and slowest in ___

Answer 56

gases; liquids; solids

Question 57

– proportionality constant that measures how easily substance moves through a particular medium

Answer 57

Diffusion coefficient

Question 58

In ___, the negative sign in the equation indicates that the flux moves ___ a concentration gradient.

Answer 58

Diffusion coefficient; down

Question 59

larger molecules have (smaller/bigger) diffusion coefficients

Answer 59

smaller

Question 60

If the initial conditions are such that all the solute molecules are concentrated at the starting position, then the concentration front moves __from the starting position

Answer 60

away

Question 61

As the substance diffuses away from the starting point, the concentration gradient becomes ____ steep and thus net movement becomes ___.

Answer 61

less; slower

Question 62

diffusion in solutions can be effective within ____but is far too slow for ___ over long distances

Answer 62

cellular dimensions; mass transport

Question 63

_____ Drives Long-Distance Water Transport

Answer 63

Pressure-Driven Bulk Flow

Question 64

____ – second process by which water moves; a concerted movement of groups of molecules en masse, most often in response to a ___

Answer 64

Bulk Flow or Mass Flow; pressure gradient.

Question 65

In a bulk flow through a tube, the rate of volume flow depends on the ___of the tube, the ____of the liquid and the ___ that drives the flow.

Answer 65

radius ; viscosity ; pressure gradient.

Question 66

Therefore, the pressure-driven bulk flow is very sensitive to the ___of the tube. If the radius is doubled, the volume flow rate increases by a factor of ___

Answer 66

radius ; 16 (2^4)

Question 67

____ of water is the predominant mechanism responsible for long-distance transport of water in the ____.

Answer 67

Pressure-driven bulk flow; xylem

Question 68

pressure-driven bulk flow is (independent/dependent) of solute concentration gradients, as long as viscosity changes are ___.

Answer 68

independent; negligible

Question 69

____is Driven by a Water Potential Gradient

Answer 69

Osmosis

Question 70

Membranes of plant cells are ____; that is, they allow the movement of water and other small uncharged substances across them more readily than the movement of larger solutes and charged substances.

Answer 70

selectively permeable

Question 71

In ____, substances move down a concentration gradient; in ____, substances move down a pressure gradient; in ___, both types of gradients influence transport

Answer 71

simple diffusion; pressure-driven bulk flow; osmosis

Question 72

The Chemical Potential of Water Represents the ___ Status of Water

Answer 72

Free-Energy

Question 73

Processes such as biochemical reactions, solute accumulation, and long-distance transport are all driven by an input of ___ into the plant.

Answer 73

free energy

Question 74

___ (of water) - a quantitative expression of the free energy associated with water.

Answer 74

Chemical potential

Question 75

- a measure of the free energy of water per unit volume.

Answer 75

Water Potential

Question 76

The major factors influencing the water potential in plants are

Answer 76

(solutes) concentration, pressure, and gravity

Question 77

____represents the effect of dissolved solutes on water potential.

Answer 77

Solute potential or osmotic potential

Question 78

___reduce the free energy of water by diluting the water.

Answer 78

Solutes

Question 79

mixing of solutes and water increases the disorder of the system and thereby lowers free energy.

Answer 79

entropy effect;

Question 80

osmotic potential is (independent/dependent) of the specific nature of the solute.

Answer 80

independent

Question 81

___pressures raise the water potential; ___pressures reduce it.

Answer 81

Positive; negative

Question 82

The positive hydrostatic pressure within cells is the pressure referred to as ____

Answer 82

turgor pressure

Question 83

The value of pressure potential can also be ___, as is the case in the xylem and in the walls between cells, where a ___, can develop.

Answer 83

negative; tension, or negative hydrostatic pressure

Question 84

___causes water to move downward unless the force of gravity is opposed by an equal and opposite force.

Answer 84

Gravity

Question 85

___ and ____ are the two major factors that affect water potential, although when large vertical distances are involved, ___is also important.

Answer 85

Solute concentration and hydrostatic pressure; gravity

Question 86

Plant cells come into water potential equilibrium with their local environment by ____ or ___

Answer 86

absorbing or losing water.

Question 87

The rate of water transport across a membrane depends on the _____ across the membrane and the ___of the membrane.

Answer 87

water potential difference; hydraulic conductivity

Question 88

In addition to its importance in transport, ____is a useful measure of the water status of plants.

Answer 88

water potential

Question 89

Write down other concepts in water and plant cells (6)

Answer 89

a. Water Enters the Cell along a Water Potential Gradient b. Water Can Also Leave the Cell in Response to a Water Potential Gradient c. Small Changes in Plant Cell Volume Cause Large Changes in Turgor Pressure d. Water Transport Rates Depend on Driving Force and Hydraulic Conductivity e. The Water Potential Concept Helps Us Evaluate the Water Status of a Plant f. The Components of Water Potential Vary with Growth Conditions and Location within the Plant