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Plant Physiology > 3 Plant-Water Relations > Flashcards

3 Plant-Water Relations Flashcards

1
Q

Water plays a crucial role in the life of the plant. For every gram of organic matter made by the plant, approximately _ g of water is absorbed by the roots, transported through the plant body and lost to the atmosphere.

A

500

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2
Q

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

A

turgor

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3
Q

Turgor pressure is essential for many physiological processes,
including (5)

A
  • cell enlargement,
  • gas exchange in the leaves,
  • transport in the phloem, and
  • various transport processes across membranes
  • contributes to the rigidity and mechanical stability of nonlignified plant tissues
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4
Q
  • Water makes up most of the mass of plant cells
  • Water typically constitutes _ % of the mass of growing plant tissues
  • each cell contains a large-water filled vacuole
  • cells the cytoplasm makes up only _ % of the cell volume; the remainder is vacuole
A

80 to 95
5 to 10

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5
Q

Water is the most abundant and arguably the best solvent known

  • As a solvent, it makes up the _ for the movement of molecules within and between cells and greatly influences the structure of _ , and other cell constituents
  • Water forms the environment in which most of the biochemical reactions of the cell occur, and it directly participates in many essential chemical reactions
A
  • medium
  • proteins, nucleic acids, polysaccharides
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6
Q

Plants continuously absorb and lose water

  • Most of the water lost by the plant evaporates from the leaf as the CO2 needed for photosynthesis is absorbed from the atmosphere
  • On a warm, dry, sunny day a leaf will exchange up to _ % of its water in a single hour
  • During the plant’s lifetime, water equivalent to _ times the fresh weight of the plant may be lost through the leaf surfaces.
  • water loss is called _
A
  • 100
  • 100
  • transpiration
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7
Q

Transpiration is an important means of _ input from sunlight

  • Heat dissipates because the water molecules that escape into the atmosphere have _ than-average energy, which breaks the bonds holding them in the liquid
  • When these molecules escape, they leave behind a mass of molecules with lower-than-average energy and thus a cooler body of water.
  • For a typical leaf, nearly _ of the net heat input from sunlight is dissipatedby transpiration.
  • the stream of water taken up by the roots is an important means of
    bringing _ to the root surface for absorption.
A
  • dissipating the heat
  • higher
  • half
  • dissolved soil minerals
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8
Q

property of water that made it act as a best solvent and can transport through the body of the plant

A

polarity
polar structure of water molecule

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9
Q

Diagram of the Water Molecule

A
  • two intramolecular hydrogen–oxygen bonds form an angle of 105°
  • opposite partial charges (δ– and δ+) on the water molecule lead to the formation of intermolecular hydrogen bonds with other water molecules
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10
Q
  • Because the oxygen atom is more electronegative than hydrogen, it tends to attract the electrons of the covalent bond.
  • This attraction results in a partial negative charge at the _ end of the molecule and a partial positive charge at _
A
  • oxygen
  • each hydrogen
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11
Q
  • weak electrostatic attraction between molecules;
  • responsible for many of the unusual properties of water
A

Hydrogen Bond

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12
Q

The Polarity of Water Molecules Gives Rise to _ and makes water an _

A
  • Hydrogen Bonds
  • excellent solvent
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13
Q

versatility of water as solvent is due to

A
  • small size of water molecule
  • its polar nature
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14
Q

Polarity makes water a particularly good solvent for ionic substances and for molecules such as sugars and proteins that contain polar _

A

—OH or —NH2 groups

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15
Q

what 3 properties of Water Result from Hydrogen Bonding

A
  • thermal property
  • Cohesive property
  • Adhesive Properties
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16
Q

The extensive hydrogen bonding between water molecules results in unusual thermal properties, such as _

A
  • high specific heat
  • high latent heat of vaporization
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17
Q
  • the heat energy required to raise the temperature of a substance by a specific amount.
A

Specific heat

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18
Q

– the energy needed to separate molecules from the liquid phase and move them into the gas phase at constant temperature

A

Latent heat of vaporization

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19
Q

– a process that occurs during transpiration [important component of temperature regulation in palnts

A

Latent heat of vaporization

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20
Q

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

A

high latent heat of vaporization

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21
Q
  • Water molecules at an air–water interface are more strongly attracted to neighboring water molecules than to the gas phase-water surface.
  • As a consequence of this unequal attraction, an air–water interface _ its surface area.
  • To increase the area of an air–water interface, hydrogen bonds must be _ , which requires an input ofenergy.
A

minimizes
broken

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22
Q

the energy required to increase the surface area.

A

Surface tension

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23
Q

Surface tension not only influences the _ but also may
create a _ in the rest of the liquid

A

shape of the surface
pressure

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24
Q

Surface tension at the evaporative surfaces of leaves generates the physical forces that _ through the plant’s _ system

A

pull water
vascular

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25
Q

the mutual attraction between molecules

A

Cohesion

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26
Q

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

A

Adhesion

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27
Q

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

A

Capillarity

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28
Q

Cohesion gives water a _

A

High Tensile strength

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29
Q

the maximum force per unit
area that a continuous column of water can withstand before breaking

A

tensile strength

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30
Q

unit of measurement of pressure

A

pascals (Pa)
[more convenient is megapascals
(MPa = approximately 9.9 atmospheres)]

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31
Q

Function of Water in Plant Life

Water is a constituent of _

A

protoplasm

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32
Q

Function of Water in Plant Life

Water acts as a solvent.

Plants can absorb nutrients when these nutrients are _ in water

A

dissolved

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33
Q

Function of Water in Plant Life

Water is used for _ from the soil to green plant tissues.

A

transpiration carrier of nutrients

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34
Q

Function of Water in Plant Life

They are used for _ and the end product is also conveyed through water to various plant parts

A

photosynthesis

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35
Q

Function of Water in Plant Life

Water forms over _ % of the plant body by green or fresh weight basis.

A

90

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36
Q

Function of Water in Plant Life

Plants can _ through photosynthesis only in the presence of water in their
system

A

synthesis food

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37
Q

Function of Water in Plant Life

Water helps to maintain the _ . Water helps in _ due to turgor pressure and cell division which ultimately increase the growth of plant.

A

turgidity of cell walls
cell enlargement

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38
Q

Function of Water in Plant Life

Water is essential for the _ , growth of plant roots, and _ of soil organism

A

germination of seeds
nutrition and multiplication

39
Q

Function of Water in Plant Life

Water is essential in _ in the plant. It helps in the conversion of starch to sugar

A

hydraulic process

40
Q

Function of Water in Plant Life

Water helps in the transpiration, which is very essential for maintaining the _ from the soil.

A

absorption
of nutrient

41
Q

Function of Water in Plant Life

Water regulates the _ and cools the plant.

A

temperature

42
Q

Function of Water in Plant Life

Water helps in the _ reaction in soil.

A

chemical, physical and biological

43
Q

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

A

Aquaporins

44
Q

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

A

Aquaporins

aquaporins may alter rate of water movement across movement but not the direction off transport or driving force for water movement

45
Q

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

A

kinetic energy

46
Q

molecules intermingle as a result of their random _

A

thermal agitation

47
Q

This random motion is called _ . As long as other forces are not acting on the molecules,

A

diffusion

48
Q

diffusion causes the net movement of molecules from
regions of high concentration to regions of low concentration—that is, down a _

A

concentration gradient

49
Q

– German scientist discovered that the rate of diffusion is
directly proportional to the concentration gradient

A

Adolf Fick (1880s)

50
Q

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

A

Flux density (Js)

51
Q
  • proportionality constant that measures how easily substance moves through a particular medium;
  • characteristic of the substance and depends on the medium
  • the negative sign in the equation
    indicates that the flux moves down a concentration gradient.
A

Diffusion coefficient

movement is in response to a concentration gradient not for movement
in response to other forces such as pressure, electric fields, etc

52
Q

Diffusion is Rapid over _ Distances but Extremely Slow over _ Distances

A

short
Long

53
Q

diffusion in solutions can be effective within _ dimensions but is far too slow for mass transport over long distances.

A

cellular

54
Q

Pressure-Driven Bulk Flow Drives _ -Distance Water Transport

A

Long

55
Q
  • second process by which water moves;
  • a concerted movement of groups of molecules en masse, most often in response to a pressure gradient.
A

Bulk Flow or Mass Flow

56
Q

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

A
  • radius
  • viscosity
  • pressure gradient
57
Q

If the radius is doubled, the volume flow rate increases by a factor of _

A

16 (2^4)

58
Q

_ of water is the predominant mechanism responsible for long-distance transport of water in the xylem

A

Pressure-driven bulk flow

It also accounts for much of the water flow through the soil and through the cell walls of plant tissues.

59
Q

Osmosis is Driven by a _

A

Water Potential Gradient

60
Q
  • In simple diffusion, substances move down a concentration gradient;
  • in pressure-driven bulk flow, substances move down a pressure gradient;
  • in osmosis, _ influence transport.
A

both types of gradients

61
Q

The Chemical Potential of Water Represents the _ of Water

A

Free-Energy Status

62
Q

All living things, including plants, require a continuous input of_ to maintain and repair their highly organized structures, as well as to grow and reproduce

A

free energy

63
Q

Processes such as _ are all driven by an input of free energy into the plant.

A
  • biochemical reactions,
  • solute accumulation,
  • long-distance transport
64
Q

a quantitative expression of the free energy
associated with water.

A

Chemical potential (of water)

65
Q
  • a measure of the free energy of water per unit volume
A

Water Potential

66
Q

Three Major Factors Contribute to Cell Water Potential

A
  1. solutes
  2. pressure
  3. gravity
67
Q

represents the effect of dissolved solutes on
water potential.

A

Solute potential or osmotic potential

68
Q

Solutes reduce the free energy of water by _

A

diluting the water.

69
Q

This is primarily an entropy effect; that is, the mixing of solutes and water increases the disorder of the system and thereby _

A

lowers free energy

This means that the osmotic potential is independent of the specific nature of the
solute.

70
Q

Hydrostatic pressure of the solution

A

Pressure

71
Q

Sometimes called pressure potential

A

Pressure

72
Q

Positive pressures _ the water potential; negative pressures _ it

A

raise
reduce

73
Q

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

A

turgor
pressure

74
Q

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

A

tension

75
Q

causes water to move downward unless its force is opposed by an
equal and opposite force

A

gravity

76
Q
  • _ are all strongly influenced by water potential and its components.
  • Like the body temperature of humans, _ is a good overall indicator of plant health.
A
  • Cell growth,
  • photosynthesis,
  • crop productivity
  • water potential
77
Q

Water Enters the Cell along a _

A

Water Potential Gradient

78
Q

Water Can Also Leave the Cell in Response to a _

A

Water Potential Gradient

79
Q

Small Changes in Plant Cell Volume Cause Large Changes in _

A

Turgor Pressure

80
Q

Water Transport Rates Depend on _

A

Driving Force and Hydraulic Conductivity

81
Q

The _ Concept Helps Us Evaluate the Water Status of a Plant

A

Water Potential

82
Q

The Components of Water Potential Vary with _ within the Plant

A

Growth Conditions and Location

83
Q

Water is important in the life of plants because it makes up the _ and _ in which most biochemical processes essential for life take place.

A

matrix
medium

84
Q

The _ and _ of water strongly influence the structure and properties of
proteins, membranes, nucleic acids, and other cell constituents

A

structure
properties

85
Q

In most land plants, water is continually lost to the _ and taken up from the _.

A

atmosphere
soil

86
Q

The movement of water is driven by a _ , and water may move
by diffusion, by bulk flow, or by a combination of these fundamental transport mechanisms

A

reduction in free energy

87
Q

Water diffuses because molecules are in constant _, which tends to even out concentration differences.

A

thermal agitation

88
Q

Water moves by bulk flow in response to a _, whenever there is a suitable pathway for bulk movement of water.

A

pressure difference

89
Q

Osmosis, the movement of water across membranes, depends on a gradient in free energy of water across the membrane—a gradient commonly measured as a
_.

A

difference in water potential

90
Q

_ are the two major factors that affect water potential, although when large vertical distances are involved, gravity is also important

A

Solute concentration and hydrostatic pressure

91
Q

Plant cells come into water potential equilibrium with their local environment by _

A

absorbing or losing water

92
Q

Usually this change in cell volume results in a change in _ , accompanied by minor changes in _.

A

cell water potential
cell solute potential

93
Q

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

A

water potential difference
hydraulic conductivity

94
Q

In addition to its importance in transport, water potential is a useful measure of the _ of plants.

A

water status

Plant Physiology (4 decks)

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