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Biology 101 flashcards
1
Q

outcome of bonsai experiment

A

fertilization did not increase the growth rate of the small trees
they didnt exhibit a dwarf phenotype due to nutrient deprivation
might be the small root structure

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2
Q

explain the two worlds land plants live in

A

above ground = shoot systems acquire sunlight and co2

below ground = root systems acquire water and minerals

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3
Q

what did algal ancestors of plants absorb

A

water, minerals and co2 from the water they lived in

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4
Q

what did earliest land plants have

A

nonvascular plants that grew photosynthetic shoots above the shallow water
leafless shoots had waxy cuticles and few stomata = allowed them to avoid excess water loss and permits some exchange of co2 and o2

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5
Q

early land plants anchoring and absorbing functions were assumed by

A

base of the stem or by threadlike rhizoids

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6
Q

land plants evolved and increased in number lead to

A

competition for light water and nutrients

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7
Q

evolution of vascular tissues like xylem and phloem lead to

A

made possible the development of extensive roots and shoots systems that carry out long distance transport

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8
Q

what does xylem do

A

transports water and minerals from roots to shoots

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9
Q

what does phloem do

A

transports products of photosynthesis from where they are made or stores to where they need to be

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10
Q

describe the plants that had an advantage in absorbing light

A

taller plants with broad flat appendages

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11
Q

describe the plants that need more water

A

increased surface area (broad, flat appendages) lead to more evaporation

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12
Q

describe the plants that require more anchorage

A

larger shoots

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13
Q

what did greater shoot heights do

A

further separated the top of photosynthetic shoots from the nonphotosynthetic parts below ground

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14
Q

what did natural selection favour

A

plants capable of efficient long distance transport of water minerals and products of photosynthesis

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15
Q

what do the adaptations have to do

A

compromise between enhancing photosynthesis and minimizing water loss

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16
Q

diversity in plants is due to

A

differences in branching patterns, dimensions, shapes, and orientations of the shoot’s two components

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17
Q

name the shoots two components

A

stems and leaves

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18
Q

what does shoot architecture facilitate

A

light capture for photosynthesis

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19
Q

what do stems do

A

supporting structures for leaves

conduits for the transport of water and nutrients

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20
Q

name the two architectural features affecting light capture

A

branching pattern and length of stems

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21
Q

describe tall plants

A

thick stems, greater vascular flow, stronger mechanical support

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22
Q

describe vines

A

rely on other objects to support their stem

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23
Q

describe woody plants

A

stems become thicker through secondary growth

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24
Q

branching enables

A

plants to harvest sunlight

for photosynthesis more effectively

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25
Q

why is there variation in branching patterns

A

a finite amount of energy to devote to shoot growth
most of that energy goes into branching, there is less
available for growing tall
risk of being shaded by taller plants increases

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26
Q

what do shoot architectures optimize

A

ability to absorb light

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27
Q

what do variations in leaf size and structure cause

A

much of the outward diversity in plant form

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28
Q

where are species with largest leaves found

A

tropical rain forests

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29
Q

where are species with smallest leaves found

A

dry or very cold environments

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30
Q

arrangement of leaves on stems is called

A

phyllotaxy

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31
Q

describe phyllotaxy

A

genetically determined and programmed by the shoot apical meristem and is specific to each species

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32
Q

describe different 3 types of phyllotaxy

A

one leaf per node (alternate, or spiral, phyllotaxy)
two leaves per node (opposite phyllotaxy)
more leaves per node (whorled phyllotaxy)

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33
Q

describe phyllotaxy of angiosperms

A

alternate phyllotaxy
leaves arranged in an ascending spiral around the stem
successive leaf emerging 137.5° (angle minimizes shading of lower leaves)

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34
Q

plant features that…

A

reduce self-shading increase light capture

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35
Q

measurement for light capture

A

leaf area index
ratio of the total upper leaf surface of a single plant or an entire crop divided by the surface area
of the land on which the plant or crop grows
values up to 7 are common for mature crops

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36
Q

consequence of adding more leaves increasing shading of lower leaves to the point that they respire more than photosynthesize

A

nonproductive leaves or branches undergo programmed cell death and are eventually shed, a process called self- pruning

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37
Q

leaf orientation affects what

A

light capture

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38
Q

name the 2 leaf orientations

A

horizontal

vertical

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39
Q

leaf orientations in low light conditions

A

horizontal leaves capture sunlight much more effectively than vertical leaves

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40
Q

leaf orientations in high light conditions

A

horizontal orientation exposes upper leaves to overly intense light, injuring leaves and reducing photosynthesis
Vertical light rays are essentially parallel to the leaf surfaces, so no leaf receives too much light, and light penetrates more deeply to the lower leaves

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41
Q

how do the roots of many plants respond to low nitrate pockets

A

extending straight through the pockets instead of branching within them

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42
Q

how do the roots of many plants respond to rich nitrate pockets

A

often branch extensively there

synthesizing more proteins involved in nitrate transport and assimilation

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43
Q

Efficient absorption of limited nutrients is enhanced by

A

reduced competition within the root system of a plant

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44
Q

what are the evolution of mutualistic associations between roots and fungi called

A

mycorrhizae

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45
Q

describe mycorrhizae

A

Mycorrhizal hyphae provide the fungus and plant roots with an enormous surface area for absorbing water and minerals (phosphate)

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46
Q

name the 2 major pathways of transport

A

apoplast

symplast

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47
Q

describe apoplast

A

consists of everything external to the plasma membranes of living cells and includes cell walls, extracellular spaces, and the interior of dead cells such as vessel elements and tracheids

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48
Q

describes symplast

A

consists of the entire mass of cytosol of all the living cells in a plant, as well as the plasmodesmata, the cytoplasmic channels that interconnect them

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49
Q

name the 3 routes for transport within a plant tissue or organ

A

apoplastic
symplastic
transmembrane routes

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50
Q

describe apoplastic route

A

water and solutes move along the continuum of cell walls and extracellular spaces (like the way water moves through a sponge)

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51
Q

describe symplastic route

A

water and solutes move along the continuum of cytosol
route requires substances to cross a plasma membrane when they first enter the plant substances can move from cell to cell via plasmodesmata.

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52
Q

describe transmembrane route

A

water and solutes move out of one cell across the cell wall and into the neighbouring cells
requires repeated crossings of plasma membranes as substances exit one cell and enter the next

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53
Q

selective permeability of the plasma membrane controls

A

short-distance movement of substances into and out of cells

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54
Q

what types of transport do plants have

A

active and passive

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55
Q

what are plant cell membranes equipped with

A

same general types of pumps and proteins

channel proteins, carrier proteins, and cotransporters

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56
Q

difference between basic transport in animal and plant cells

A

unlike animal cells, hydrogen ions (H+) rather than sodium ions (Na+) play the primary role in basic transport in plant cells

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57
Q

what is membrane potential in plants

A

the voltage across the membrane is established mainly through the pumping of H+ by proton pumps

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58
Q

describe cotransport with H+

A

plant cells use the energy in the H+ gradient and membrane potential to drive the active transport of many different solutes
cotransport with H+ is responsible for absorption of neutral solutes
an H+/sucrose cotransporter couples movement of sucrose against its concentration gradient with movement of H+ down its electrochemical gradient
facilitates movement of ions (uptake of nitrate (NO3−) by root cells)

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59
Q

describe ion channels

A

only certain ions to pass
most channels are gated (opening or closing
in response to stimuli)
Ion channels are involved in producing electrical signals

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60
Q

absorption or loss of water. by a cell occurs by

A

osmosis
regions of high water potential to lower water potential
dependant on solute concentration

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61
Q

what is water potential

A

physical property that predicts the direction in which water will flow
water’s capacity to perform work when it moves from a region of higher water potential to a region of lower water potential

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62
Q

water potential formula

A

measured in pressure = megapascal
abbreviated psi
psi = psi p (pressure potential, directly proportional to molarity) + psi s (solute potential, osmotic potential)

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63
Q

psi of pure water in an open container

A

0 MPa

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64
Q

what is one Mpa =

A

10 times 101.3 kPa

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65
Q

internal pressure of a living plant cell due to the osmotic uptake of water is approximately

A

O.5 MPa

66
Q

effect on water potential by an increase in solutes

A

negative effect

solute potential = always negative

67
Q

describe pressure

A 
solution is being withdrawn by a syringe = negative pressure; being expelled from a syringe = positive pressure
water in living cells = positive pressure due to the osmotic uptake of water. 
the protoplast (the living part of the cell) presses against the cell wall = turgor pressure.
68
Q

what does turgor pressure do

A

critical for plant function
helps maintain the stiffness of plant tissues
the driving force for cell elongation

69
Q

water in hollow nonliving xylem cells (tracheids and vessel element)

A

negative pressure

70
Q

what is wilting

A

effects of turgor loss

result of cell losing water

71
Q

what does difference in water potential determine

A

direction of water movement across membranes

72
Q

how dow water molecules move

A

diffuse across the phospholipid bilayer

73
Q

what is aquaporins

A

the transport proteins that facilitate the transport of water molecules across membranes
channels are highly dynamic

74
Q

what is the name of long distance transport

A

bulk flow
the movement of liquid in response to a pressure gradient
higher to lower pressure

75
Q

where does bulk flow occur

A

tracheids and vessel elements of the xylem and within the sieve-tube elements of the phloem

76
Q

what is efficient bulk flow due to

A

absence or reduction of cytoplasm
perforation plates at the ends of vessel elements
porous sieve plates connecting sieve-tube elements

77
Q

where does absorption of water and minerals occur

A

root hair epidermal cells near the tips of roots

78
Q

describe absorption of water and minerals by root epidermal cells

A

The root hairs absorb the soil solution (water molecules and dissolved mineral ions)
soil solution is drawn into the hydrophilic walls of epidermal cells and moves along the cell walls and the extracellular spaces into the root cortex enhances the exposure of the cells of the cortex to the soil solution = much greater membrane surface area for absorption
active transport enables roots to accumulate essential minerals

79
Q

what must the water and minerals pass from before being transported to rest of plant

A

xylem of vascular cylinder or stele

80
Q

what does the endodermis do in terms of transport

A

last checkpoint for the selective passage of minerals from the cortex into the vascular cylinder

81
Q

describe transport through endodermis and symplast

A

minerals already in the symplast when they reach the endodermis continue through the plasmodesmata of endodermal cells and pass into the vascular cylinder

82
Q

describe transport through endodermis and apoplast

A

encounter a dead end, blocks their passage into the vascular cylinder.
barrier is the Casparian strip water and minerals cannot cross the endodermis and enter the vascular cylinder via the apoplast

83
Q

what must minerals and water passively moving through apoplast do

A

cross the selectively permeable plasma membrane of an endodermal cell before they can enter the vascular cylinder
the endodermis transports needed minerals from the soil into the xylem and keeps many unneeded or toxic substances out
prevents solutes that have accumulated in the xylem from leaking back into the soil solution

84
Q

what is the last segment in the soil-to-xylem pathway

A

passage of water and minerals into the tracheids and vessel elements of the xylem

85
Q

what is xylem sap

A

the water and dissolved minerals in the xylem

86
Q

where does xylem sap get transport

A

to the veins that branch throughout each leaf

87
Q

what does transporting xylem sap involve

A

loss of an astonishing amount of water by transpiration

88
Q

when do plants wilt

A

when transpired water is NOT replaced by water transported up from the roots

89
Q

what happens at night when there is almost no transpiration

A

root cells continue actively pumping mineral ions into the xylem
Casparian strip prevents the ions from leaking back out into the cortex and soil
resulting accumulation of minerals lowers the water potential within the vascular cylinder
water flows in from the root cortex, generating root pressure, a push of xylem sap.

90
Q

what is guttation

A

more water to enter the leaves than is transpired

the exudation of water droplets that can be seen in the morning on the tips or edges of some plant leaves

91
Q

what is dew

A

condensed atmospheric moisture

92
Q

xylem sap is…

A

not pushed from below by root pressure but is pulled up

93
Q

describe cohesion tension hypothesis

A

transpiration provides the pull for the ascent of xylem sap
the cohesion of water molecules transmits this pull along the entire length of the xylem from shoots to roots
xylem sap is under negative pressure or tension

94
Q

what is transpirational pull

A

Stomata on a leaf’s surface lead to a maze of internal air spaces that expose the mesophyll cells to he CO2 they need for photosynthesis
air in these spaces is saturated with water vapour the air outside the leaf is drier so water vapour in the air spaces of a leaf diffuses down its water potential gradient and exits the leaf via the stomata
loss of water vapour by diffusion and evaporation that we call transpiration

95
Q

what develops at the surface of mesophyll cell walls in the leaf

A

negative pressure potential that causes water to move up through the xylem

96
Q

what does cell wall act as

A

very thin capillary network

97
Q

what does water adhere to

A

the cellulose microfibrils and other hydrophilic components of the cell wall

98
Q

what happens because of the high surface tension of water

A

curvature of the interface induces a tension, or negative pressure potential, in the water
more water evaporates = curvature of the air-water interface increases and the pressure of the water becomes more negative
water molecules from the more hydrated parts of the leaf are then pulled toward this area, reducing the tension
pulling forces are transferred to the xylem because each water molecule is cohesively bound by hydrogen bonds

99
Q

the negative water potential of leaves provides the..

A

“pull” in transpirational pull

100
Q

Consequence of climate change

A

increasing amount
of water vapour in the atmosphere = decreases the air’s water potential
With a smaller difference between the water potentials of the air spaces and the atmosphere
transpirational pull, and therefore xylem sap transport, will diminish = insufficient water delivered to meet the photosynthetic demands of the leaves

101
Q

what does decreased xylem transport produce

A

deficiencies in essential nutrients required for the synthesis of biological molecules and growth

102
Q

what is adhesion

A

attractive force between water molecules and other polar substances
strong attraction between water molecules and the cellulose molecules in the xylem cell walls

103
Q

what is cohesion

A

attractive force between molecules of the same substance

water has an unusually high cohesive force bc hydrogen bonds

104
Q

waters cohesive force within xylem has…

A

tensile strength equivalent to that of a steel wire of similar diameter

105
Q

cohesion of water makes it possible to

A

pull a column of xylem sap from above without the water molecules separating

106
Q

describe pulling of xylem sap

A

Water molecules exiting the xylem in the leaf tug on adjacent water molecules, and this pull is relayed, down the entire column of water in the xylem
the strong adhesion of water molecules to the hydrophilic walls of xylem cells helps offset the downward force of gravity

107
Q

what is cavitation

A

the formation of a water vapour pocket
common in wide vessel elements
can occur during drought stress or when xylem sap freezes in winter
air bubbles resulting from cavitation expand and block water channels of the xylem (hydraulic failure)

108
Q

Interruption of xylem sap by cavitation

A

not always permanent

chain of water molecules can detour around the air bubbles through pits between adjacent tracheids or vessel elements

109
Q

what adds a layer of new xylem each year

A

secondary growth

110
Q

what is the function of older secondary xylem

A

no longer transport water

provides support

111
Q

how is bulk flow different from diffusion

A

driven by differences in pressure potential not solute potential
flow does not occur across plasma membranes of living cells instead = hollow dead cells
way faster
moves whole solution together
plant expends no energy to lift xylem sap by bulk flow
absorption of sunlight drives most of transpiration

112
Q

what is translocation

A

transport of the products of photosynthesis

carried out by the phloem

113
Q

what are sieve-tube elements

A

In angiosperms, the specialized cells that are conduits for translocation

114
Q

what are inbetween sieve tube element cells

A

sieve plates, structures that allow the flow of sap along the sieve tube

115
Q

what is phloem sap

A

aqueous solution that flows through sieve tubes
made of sugar
contains amino acids, hormones and minerals

116
Q

how does phloem sap move

A

phloem sap moves from sites of sugar production to sites of sugar use or storage

117
Q

What is a sugar source

A

plant oran that is a net producer of sugar by photosynthesis or by breakdown of starch

118
Q

what is a sugar sink

A

organ that is a net consumer or depository of sugar

growing roots, buds, stems, fruits

119
Q

what is a storage organ

A

tuber or a bulb
may be a source or a sink, depending on the season stockpiling carbohydrates in the summer = sugar sink
breaking dormancy in the spring = sugar source (starch is broken down to sugar, which is carried to the growing shoot tips)

120
Q

where do sinks receive sugar from

A

Nearest sugar sources

121
Q

direction of transport for each sieve tube depends on

A

locations of the sugar source and sugar sink that are connected by that tube

122
Q

describe route through the sieve tube elements

A

sugar is loaded into them
sugar is unloaded at sink end of tube
process varies by species and organ
concentration of free sugar in sink is always lower than in the sieve tube because unloaded sugar is consumed during growth and metabolism of the cells of the sink or converted to insoluble polymers like starch

123
Q

result of sugar gradient concentration =

A

sugar molecules move by facilitated diffusion from phloem to sink tissues and water follows by osmosis

124
Q

Consequences of loss of phloem function

A

sugar transport becomes severely compromised and the end result is typically death of the tree within 5 years of infection

125
Q

how does phloem sap move through sieve tubes of angiosperms

A

by bulk flow driven by positive pressure = pressure flow

126
Q

describe pressure flow process

A

1=sugars are loaded into the phloem sap by source cells
2=movement of solutes lowers water potential of phloem sap in region, causes water to enter nearby cells and xylem, resulting increase in water pressure forces phloem sap to move along tubes
3=at sink cells, sugars are unloaded
4=increases water potential and causes water to leave phloem sap and enter neighbouring cells and xylem vessels, xylem recycles the way from sink to source

127
Q

what do sinks vary in

A

energy demands and capacity to unload sugars

128
Q

what is self thinning

A

more sinks than can be supported by sources

plant might abort some flowers, seeds, or fruits

129
Q

true or false

transport needs of a plant cell typically change during its development

A

true

130
Q

what does water stress activate

A

signal transduction pathways that greatly alter the membrane transport proteins governing the overall transport of water and minerals

131
Q

what is symplast responsible for

A

dynamic changes in plant transport processes

132
Q

what are plasmodesmata

A

highly dynamic components of the symplast
can change in permeability and number
open or close rapidly in response to changes in turgor pressure, cytosolic Ca2+ levels, or cytosolic pH
form during cytokinesis or much later

133
Q

what can plasmodesmata do when a leaf matures from sink to source

A

either close or are eliminated, causing phloem unloading to cease

134
Q

what do plant viruses produce

A

viral movement proteins that cause plasmodesmata to dilate, enabling viral RNA to pass between cells
plant cells themselves regulate plasmodesmata as part of a communication network
Viruses subvert this network by mimicking the cell’s regulators of plasmodesmata

135
Q

what are symplastic domains

A

high degree of cytosolic interconnectedness exists only within certain groups of cells and tissues
informational molecules, such as proteins and RNAs, coordinate development between cells within each symplastic domain

136
Q

phloems transport is

A

systemic

transports macromolecules lile proteins and various types of RNA

137
Q

electrical signalling in phloem

A

dynamic feature
stimulus in one part of a plant can trigger an electrical signal in the phloem that affects another part, where it may elicit a change gene transcription, respiration, photosynthesis, phloem unloading, or hormonal levels
the phloem can serve a nerve-like function

138
Q

what increases rate of photosynthesis and also increases water loss by stomata

A

large surface areas and high surface-to-volume ratios

139
Q

what limits water loss

A

waxy cuticle

guard cells control the diameter of the stoma by changing shape

140
Q

amount of water lost by leaf depends on

A

number of stomata and the average size of their pores.

141
Q

stomatal density of a leaf is controlled by

A

genetic and environmental control

142
Q

what leads to increased density

A

high light exposures and low CO2 levels during leaf development

143
Q

in angiosperms cell wall of guard cells is

A

uneven in thickness, and the cellulose microfibrils are oriented in a direction that causes the guard cells to bow outward when turgid

144
Q

when cells loose water the guard cells

A

become less bowed and pore closes

145
Q

changes in turgor pressure in guard cells come from

A

reversible absorption and loss of K+

146
Q

Stomatal closing results from

A

loss of K+ from guard cells to neighbouring cells, which leads to an osmotic loss of water

147
Q

what do aquaporins do

A

help regulate the osmotic swelling and shrinking of guard cells

148
Q

stomata during day and night

A

stomata are open during the day and mostly closed at night

149
Q

stomatal opening at dawn

A

light, CO2 depletion, and an internal “clock” in guard cellds

150
Q

explain how stomata open with light

A

stimulates guard cells to accumulate K+ and become turgid triggered by blue light receptors stimulates proton pumps

151
Q

explain how stomata open with CO2 depletion

A

CO2 concentrations decrease during the day, the stomata progressively open if sufficient water is supplied to the leaf

152
Q

explain how stomata open internal clock

A

Cycles with intervals of approximately 24 hours are called circadian rhythms

153
Q

what causes stomata to close during day

A

Environmental stresses, such as drought, high tempera- ture, and wind

154
Q

plant has a water deficiency

A

guard cells may lose turgor and close stomata
hormone called abscisic acid (ABA) leaves
reduces wilting but also restricts CO2 absorption

155
Q

how do plants respond to mild drought stress

A

rapidly closing stomata

156
Q

how do plants respond to prolonged drought stress

A

leaves can become severely wilted and irreversibly injured

157
Q

Transpiration also results in…

A

evaporative cooling
lower a leaf’s temperature by 10°C compared with the surrounding air
cooling prevents the leaf from reaching temperatures that could denature enzymes involved in photosynthesis and other metabolic processes

158
Q

what is a major determinant of plant productivity

A

water availability

159
Q

plants adapted to arid

A

xerophytes

160
Q

adaptations of xerophytes

A

unusual physiological or morphological adaptations
stems of many xerophytes are fleshy, they store water for use during long dry periods
crassulacean acid metabolism (CAM), a specialized form of photosynthesis - takes place in CO2 at night = he stomata can remain closed during the day

bio 1 (16 decks)

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