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IB BIOLOGY 2017 EXAM > Plant Biology > Flashcards

Plant Biology Flashcards

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1
Q

Explain the role of auxin in phototropism

A

auxin is a plant hormone;
produced by the tip of the stem/shoot tip;

causes transport of hydrogen ions from cytoplasm to cell wall;
decrease in pH / H+ pumping breaks bonds between cell wall fibres;

makes cell walls flexible/extensible/plastic/softens cell walls;
auxin makes cells enlarge/grow;

gene expression also altered by auxin to promote cell growth;

(positive) phototropism is growth towards light;
shoot tip senses direction of (brightest) light;
auxin moved to side of stem with least light/darker side
causes cells on dark side to elongate/cells on dark side grow faster;

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2
Q

Describe the process of mineral ion uptake into roots.

A

absorbed by root hairs / through epidermis
root hairs increase the surface area for absorption
uses active transport / uses ATP / uses energy
use of proteins / pumps to move ions across membrane
against concentration gradient / diffusion gradients into cell / root
can enter cell wall space / be drawn through cell walls / apoplastic pathway
selective / only specific ions absorbed

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3
Q

Describe how water is carried by the transpiration stream

A

transpiration is water loss (from plant) by evaporation;
flow of water through xylem from roots to leaves is the transpiration stream;
evaporation from spongy mesophyll cells;
replaced by osmosis from the xylem;
(diffusion of water vapour) through stomata;
water lost replaced from xylem / clear diagram showing movement of water from xylem through cell(s) (walls) to air space;
water pulled out of xylem creates suction/low pressure/tension; transpiration pull results;
water molecules stick together/are cohesive;
due to hydrogen bonding/polarity of water molecules;
xylem vessels are thin (hollow) tubes;
adhesion between water and xylem due to polarity of water molecules;
creates continuous column/transpiration stream;

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4
Q

Explain how abiotic factors affect the rate of transpiration in a terrestrial plant

A

less transpiration as (atmospheric) humidity rises
smaller concentration gradient ( of water vapour)
more transpiration as temperature rises
faster diffusion / more kinetic energy (of water molecules)
faster evaporation (due to more latent heat available)
more transpiration as wind (speed) increases
humid air / water vapour blown away from the leaf
increasing the concentration gradient (of water vapour)
more transpiration in the light
due to light causing stomata to open
wider opening with brighter light hence more transpiration
CAM plants opposite
narrower stomata with high carbon dioxide concentration hence less transpiration

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5
Q

adaptations of xerophytes

A

xerophytes are plants that live in dry conditions;

reduced leaves/spines to prevent water loss (by transpiration);

rolled leaves to prevent water loss / stomata on the inside / sunken stomata;

thick waxy cuticle/hairs on leaves to prevent water loss (by transpiration);

reduced stomata to prevent water loss (by transpiration) /
stomata on one side of leaf;
d
eep/widespread roots to obtain more water;

special tissue for storing water;

take in carbon dioxide at night / CAM plant to prevent water loss;

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6
Q

the role of the phloem in the active translocation

A
  • living tissue
  • composed of companion cells / sieve tube members
    companion cells involved in ATP production
  • sucrose / amino acids / assimilate / products of photosynthesis transported
  • bi-directional transport
  • source / leaves to sink / fruits / roots /storage organs / named storage organ
  • pressure flow hypothesis / movement of water into phloem causes transport
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7
Q

Explain the functions of the different tissues of a leaf

A

cuticle (produced by epidermis) prevents water loss
epidermis protects cells inside the leaf
stomata (in epidermis) for gas exchange
palisade parenchyma / mesophyll / layer for photosynthesis
spongy parenchyma / mesophyll / layer for photosynthesis
air spaces for diffusion of O2 / CO2 / gases
spongy mesophyll for gas exchange / absorption of CO2
xylem transports water / mineral salts / ions to the leaves
phloem transports products of photosynthesis / sugars (to flowers / new leaves / stem / roots / fruit)
stomata allow transpiration (which helps transport of mineral nutrients)
guard cells open and close stomata
guard cells close stomata to reduce transpiration

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8
Q

Outline the adaptations of plant roots for absorption of mineral ions from the soil.

A

mineral ions are absorbed by active transport;
large surface area;
branching (increases surface area);
root hairs;
root hair cells have carrier protein/ion pumps (in their plasma membrane);
(many) mitochondria in root (hair) cells;
to provide ATP for active transport;
connections with fungi in the soil/fungal hyphae;

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9
Q

Explain how abiotic factors affect the rate of transpiration in a terrestrial plant.

A

less transpiration as (atmospheric) humidity rises
smaller concentration gradient ( of water vapour)

more transpiration as temperature rises
faster diffusion / more kinetic energy (of water molecules)
faster evaporation (due to more latent heat available)

more transpiration as wind (speed) increases
humid air / water vapour blown away from the leaf
increasing the qconcentration gradient (of water vapour)

more transpiration in the light
due to light causing stomata to open
wider opening with brighter light hence more transpiration

CAM plants opposite
narrower stomata with high carbon dioxide concentration hence less transpiration

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10
Q

List abiotic factors which affect the rate of transpiration in a typical mesophytic plant.

A

light
temperature
wind
humidity

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11
Q

transpiration

A

is the germ given to the loss of water vapour from leaves and other aerieal parts of the plant which is replaced by water absorption

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12
Q

cuticle

A
  • outermost layer of a leaf

- protects the plant from water loss and insect invasion

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13
Q

epidermis

A

secondary outermost leayer that protects the plant

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14
Q

vascular tissue

A

-phloem
-xylem
together in vascular bundles

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15
Q

xylem

A
  • brings water to the leaves

- its red and dead

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16
Q

phloem

A
  • carries the products of photosynthesis to the rest of the plant
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17
Q

palisade mesophyll

A
  • densely packed region of cylindrical cells in upper portion of leaf
  • contain many chloroplasts for photosynthesis
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18
Q

spongy mesophyll

A
  • loosely packed cells with few chloroplasts

- many air spaces for gas exchange

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19
Q

stomata

A

are pores that are on the bottom of the leaf surface for oxygen and carbon dioxide exchange between leaf and surrounding environement
- on bottom to allow for less light/temperature to minimize water loss

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20
Q

guard cells

A

specialized cells that control the opening and closing of the stomata
- have uneven cell wall thickness

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21
Q

tracheids

A

dead cells in the xylem that taper at the ends and connec to one another to form a continious column

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22
Q

xxlem vessel elements

A

cells involving water transport; also dead and have thick lignified secondary walls

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23
Q

xylem transport + function

A
  • transports water from roots to upper parts of the plant and supports the plant (by transpiration)
  • any water lost used to cool leaves and stems
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24
Q

xylem primary walls

A

pits and pores for lateral water movement

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25
Q

xylem secondary walls

A

lignin often interupted by areas of the primary walls

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26
Q

lignin

A

complex organic compounds that greatly strengths cell wall of vascular plant

  • also water profs plant and add protection against pathogens
  • primary cell wall made up of cellulose; in some plants they form a secondary cell wall of lignin
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27
Q

stomata and guard cell action

A
  • stomata can only be closed on short-term basis in reponse to turgor pressure of the surrounding guard cells
  • when water enters the cell, guard cells bulge and their cell wall thickens which opens the stoma
  • when the plant loses water; guard cells sag and that closes the stoma
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28
Q

hormone involved in stomata action

A

abscisic acid; plant hormone that causes potassium ions to diffuse rapidly out of guard cels for stomatal closure
-produced in roots during times of water deficiency

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29
Q

how does water loss/gain occur in the guard cell

A

-water loss/gain is due to potassium ion transport that triggers ATP pumps (solute concentration causes osmosis)

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30
Q

what affects stomatal opening and closing?

A
  • Carbon dioxide levels
  • Circadian rhythms
  • Hormonal changes
  • Humidity and droughts
  • Temperature
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31
Q

turgor definition

A

refers to pressure in a cel that liquid exerts on the membrane and/or cell wall

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32
Q

cohesion-tension theory

A
  • explains the movement of water vertically in the plant using intermoleculer attraction like cohesion and adhesion
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33
Q

transpiration process

A
  1. water moves down concentration gradient (spaces within leaf have high water vapour concentration so water moves to atmosphere where there is a lower water concentration); water leaves by evaporation
  2. water lost by transpiraiton replaced by water from vessels (replacing water from vessels maintains a high water vapour concentration in air spaces of leaf)
  3. the vessel water column is manintained by cohesion and adhesion (cohesion involves hydrogen bonds between water molecules and adhesion involves hydrogen bonds between water molecules and xylem vesel sides)
  4. tension occurs in the columns of water in the xylem
    (loss of water in leaves replaced by water xylem so water flow is continous because of cohesion and adhesion)
  5. water is pulled from the root cortex into xylem cells
    (cohesion and adhesion mantain columns under tension by transpiration)
  6. water is pulled from the soil into roots, root hair cells and roots have large surface area and water enters by osmosis
    (as a result of the tension created by transpiration and continiious maintenance of a continious column of water)
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34
Q

root and fluid movement in plant

A

Water moves into root hairs through plasma membranes from soil due to the higher solute concentration within the roots (osmosis) and into the vascular cylinder (phloem and xylem)

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35
Q

function of roots

A

provide mineral ion and water uptake for plant (absorbtion)

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36
Q

why are roots efficent?

A
  • extension branching patterns and specialised epidermal structures (such as root hairs cells that increase surface area)
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37
Q

what is the role of the root cap?

A

protects the apical meristem during primary growth of the root in the soil

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38
Q

zones of cell development in root zones

A

area of cell division
area of elongation
area of maturation

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39
Q

area of cell division in root

A

newly undifferentiated cells are formed in M phase of the cell cycle

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40
Q

area of elongation in root

A

where cells enlarge in size (G1)

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41
Q

area of maturation in root

A

where cells become functional party of plant

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42
Q

what proceses allow for mineral ions to enter the root?

A
  1. diffusion of mineral ions and mass flow of water in soil that carries these ions
  2. action of fungal hyphae
  3. active transport
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43
Q

what affects diffusion rate?

A
  1. difference in concentration
  2. length of diffusion path
  3. surface area
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44
Q

what is the action of fungal hyphase?

A
  • symbiotic relationship between root and fungi where fungi increase surface area for absorbiton and in return hav e a place to live
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45
Q

active transport action in roots

A

ions use transport proteins in membrane due to size or polarity

  • protons pumps are used to pump
  • represents a form of chemiosmosis
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46
Q

effect of light on transpiration

A

Speeds up transpiration by warming the leaf and opening stomata

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47
Q

effect of humidity on transpiration

A

Decreasing humidity increases transpiration because of the greater difference in water concentration

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48
Q

effect of wind on transpiration

A

Increases the rate of transpiration because humid air near the stomata is carried away

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49
Q

effect of temperature on transpiration

A

Increasing temperature causes greater transpiration because more water evaporates

50
Q

effect of soil water on transpiration

A

If the intake of water at the roots does not keep up with the transpiration, turgor loss occurs and the stomata close, and the transpiration rate decreases

51
Q

effect of carbon dioxide on transpiration

A

High CO2 levels in air around plant usually close the guard cells to lose turgor and the stomata to close

52
Q

xerophyte

A

plants that live in arid climates (desertes and little water)

53
Q

xerophyte LIFE CYCLE ADAPTATION

A

Perennial plants bloom only in wet season
Dormant seed can survive for many years until optimum growth conditions
Plants shed leaves/become dormant in dry season

54
Q

xerophyte METABOLIC ADAPTATIONS

A

CAM plants: CO2 is absorbed at night and stored as a 4 carbon compound

During the day, photosynthesis is optional

Stomata can close during day

55
Q

xerophyte PHYSICAL ADAPTATIONS

A

Fewer leaves and stomata

Rolled leaves and spikes, smaller leaves (decrease surface area of leaves)

Stomata in pits with hairs to increase humidity near stomata

Deeper roots to reach water

Cacti can store water in fleshy watery stems
Waxy cuticle that reduces evaporation

56
Q

halophyte

A

plants adapted to grow in water with high levels of salinity

-some being used for net generation of biofuel as the don’t compete with food crops for resources

57
Q

halphyte adaptations

A
  • Many have become succulent by storing water, thus diluting salt concentrations
  • Several species (like mangroves) secrete salt through salt glands
  • Some species are able to compartmentalize Na+ and Cl- in the vacuoles therefore preventing NaCl toxicity
  • Sunken stomata on thickened leaves reduce water loss by creating a higher humidity near the stomata. The thickened leaves often include a more developed cuticle to minimize water loss
  • Surface of area of the leaves is reduced
58
Q

phloem function

A

transports organic molecules throughout the plant from source to sink (products of photosynthesis)

59
Q

sink

A

plant organ that uses or stores sugar

e.g. roots, buds, stems, seeds, fruits

60
Q

source

A

plant organ that is the net producer of sugar, either by photosynthesis or starch hydrolysis
e.g. leaves

61
Q

phloem structure

A

made up of living cells (sieve plate with pores)

a companion cell with a nucleus and dense cytoplasm

connected to the sieve tube by plasmodesmata

and a sieve tube that lacks a nucleus or cytoplasm

62
Q

pressure-flow hypothesis

A

hydrostatic pressure cuases contents of phloem to flow towards sink

63
Q

translocation process

A
  1. Loading of sugar into the sieve tube at the source reduces the relative water concentration in the sieve tube members, causing osmosis from surrounding cells.

2/ This is achieved by active transport, energy provided by the companion cells

  1. The uptake of water at the source causes a positive hydrostatic pressure in the sieve tube, resulting the the bulk flow of phloem sap
  2. Hydrostatic pressure is reduced by sugar removal at the sieve tube at the sink. The sugars are changed at the sink to starch, which is insoluble and has no osmotic effect
  3. Xylem recycles the pure water by carrying it from the sink back to the source.
64
Q

How can aphids be used to calculate phloem transport rates?

A

Aphids are insects that use their stylet to pierce the phloem and eat the sap.

  1. Plant grown in lab and is exposed to radioactive CO2
  2. Incorporated in photosynthesis which produces radioactive sucrose
  3. Apid put on a plant
  4. Their sylhet is cut off so phloem fluid flows out
  5. The time taken for the sucrose to come out of the cut through leaf measure the rate of phloem sap movement
65
Q

types of plant tissue

A
  • dermal tissue
  • ground tissue
  • vascular tissue
  • meristamatic tissue
66
Q

dermal tissue

A

outer covering against physical and pathogenic agents

-prevents water loss

67
Q

ground trissue

A

thin-walled cells for storage, photosynthesis, support and secretion

68
Q

vascular tissue

A

phloem and xylem for water, mineral, nutrient support

-provide support

69
Q

meristimatic tissue

A

derived of aggregates of small cells with the same function as stem cells; undifferentiated and used for growth

70
Q

apical meristems

A
  • differentiated based on position in plant (primary meristem)
    occurs at roots and stems

shoot apex; apical meristem and surronding tissue which uses mitosis and cell division

stem growth increase with light and carbon dioxide exposre

71
Q

lateral meristems

A

growth in plant thickness (secondary meristem growth)

occurs at cambium; often in trees and shrubs

vascular cambium; procues secondary vascular tissue

cork cambium; produces cork cells of outer bark in trees

72
Q

plant hormones

A

Plant developments depends on communication within the plant

hormone types:

  • auxin
  • abscisic acid
73
Q

Factors that affect plant growth and development:

A

Environmental factors (day length and water availability)

Receptors (which allow plants to detect environmental factors)

Genetic makeup of plant

Hormones; chemical messengers (move through phloem or cell to cell)

74
Q

tropism?

phototropism?

A

Tropism: the growth or movement to directional external stimuli (can be positive or negative)

Phototropism: responses/growth to light

75
Q

auxin?

A

a plant growth hormone that affects the gene expression in shoots; causes cell elongation and development.

Found in the embryo of seeds, meristems of apical buds and young leaves. Only work on plants with auxin receptors.

76
Q

how does auxin work?

A

Affects the patterns of gene expression

Redistribution of available auxin to the side of the stem away from the light source.

Plant Auxin is called indoleacetic acid (IAA)

Auxin efflux pumps that move auxin out of cells closer to light (using ATP) to create a high auxin concentration in the space between cells

As a result, auxin moves down the concentration gradient into adjacent cells until (auxin influx) there is a greater conc. Of auxin in darker cells resulting in the elongation of the stem away from the light

Elongation of cells is caused by the expansion of the cell walls

77
Q

Sequence of events in stem causing it to bend towards a light source

A
  1. auxin produced by all cells in stem towards light source
  2. auxin moves by efflux pump action into nuclei of cells on the side of the stem opposite to light
  3. auxin + receptor in nuclei form a complex that activates a proton pump
  4. proton pump moves protons into spaces of cell wall
  5. these protons cause a pH drop; results in Hydrogen Bonds between cellulsoe fibres of cell wall breaking
  6. results in elongation of cell wall away from light source
78
Q

what are auxins involved in?

A
  • cell division stimulation in most meristamtic tissue
  • xylem and phloem differentiation
  • lateral root development in tissue cultures
  • lateral bud growth suppresion when present in apical bud
  • growth of flower parts stimulation
  • fruit production without pollination induction
79
Q

micropropagation

A

Using knowledge of hormones and meristems to clone plants to produce large numbers of progeny

  • involves placing shoot apexes into nutrient agar gels with growth hormones to get a certain quantitiy of cloned plants
  • allows for altering of gene expression in plants to help humanity
80
Q

angiosperm

A

flowering plants

co-evolve with a pollinator species (bats, insects, birds)

81
Q

sepals

A

protect developing flower while inside bud

82
Q

petals

A

often coloful to attract pollinators

83
Q

anther

A

part of the stamen that produces male sex cells

84
Q

filament

A

stalk of the stamen that holds up the anther

85
Q

stigma

A

sticky top of the carpel where pollen lands

86
Q

style

A

structure of carpel that supports stigma

87
Q

ovary

A

base of carpel; where female sex cells develop and fertilization occurs

88
Q

male part and female part

A

male; stamen

female; carpel

89
Q

monocot

A
  • parallel venation (system of veins) in leaves
  • three flower parts/multiple of three
  • seeds contain only one cotyledon
  • vascular bundles arranged throughout stem
  • root system mainly fibrious
  • pollen grain with one opening
90
Q

dicot

A
  • netlike venation pattern in leaves
  • four or five flower parts/multiples of four or five
  • seeds contain two cotyledons
  • vascular bundles arranged as a ring in the stem
  • root system involves a taproot (main root)
  • pollen grain with three openings
91
Q

polllination

A

act of transferring pollen grains from the male anther to a flower to the female stigma

92
Q

pollination process

A

Male pollen carried by pollinators or wind to style

Most flowering plants have a mutualistic relationship with pollinators in sexual reproduction (reward pollinators with nectar)

93
Q

How do plants attract pollinators?

A

Bright colors, scent

Food

94
Q

pollinator types

A

Pollinators can be generalist or specialist (generally specialist pollinators are crossed with generalist plants and vice versa)

95
Q

types of pollination

A

self pollination

cross pollination

96
Q

self pollination

A

a pollen from the anther of the same plant falls upon its stigma (inbreeding + less variation)

97
Q

cross pollination

A

pollen carried from anther of one plant to a stigma of different plants of same species (increases variation)

98
Q

gametophyte generation

A
  • haploid

- produces the plant gametes by mitosis

99
Q

sporphyte generation

A
  • diploid

- produces spores by meisosi

100
Q

allergic rhinitis

A
  • hay fever
  • condition caused by pollen causing immune response in people
  • usually happens from wind pollinated plants
101
Q

fertilization

A

when the male and female sex cells unite in the ovule to form a diploid zygote
-When pollen grain adheres to stigma (covered in sticky substance) it grows a pollen tube

102
Q

fertilization process

A

Process:
1. Pollen germinates to produce pollen tube

  1. Pollen tube grows down style
  2. Within the growing pollen tube is the nucleus that will produce sperm
  3. The pollen tube completes its growth and enters an opening at the bottom of the ovary
  4. The sperm moves from the tube to combine with egg in ovule and form a zygote
  5. Zygote develops into seed
103
Q

seed dispersal

A

the method by which seeds are scattered from plant to a new place where they can grow and develop into a new plant

-porential new plant faces reduction in competition for limited resources by moving away from parent

Wind, water or animals can disperse seeds

104
Q

testa

A

a tough, protective outer coat

105
Q

cotyledons

A

seed leaves that function as a nutrient storage structure

106
Q

microphyle

A

a scar at the opening where the pollen tube enters the ovule

107
Q

embryo root and shoot

A

becomes the new plant when germination occurs

108
Q

maturation process of seeds

A
  • invoolves dehydration untill water content is low
  • seeds usually in dormancy period; adaptive feature of seeds
  • once conditions favourable; seeds will germinate
109
Q

germination

A

development of the seed into a functional plant

110
Q

conditions needed for germination

A

Water to rehydrate dried seed tissues

Oxygen for aerobic respiration to produce ATP

Appropriate temperature for enzyme action

Large amount of seeds due to plantlets fragility/dangers to germination

111
Q

initial process of germination

A
  1. absorbtion of water
  2. release of plant growth hormone
  3. amylase is produce; hyydrolzes starch into maltose
  4. maltose hydrolyzed to glucose for cellular respiration
  5. early glucose may also convert into cellulose for cell wall production
112
Q

photoperiodism

A

a plant’s response to light involving the relative lengths of a day and night which is an important factor in flowering control

113
Q

long day plant conditions

A
  • flowers when days are long and nights short

e. g. radish, spinach, lettuce

114
Q

short day plant conditions

A
  • flower when days are shorter

e. g. poinsettias and asters

115
Q

day neutral plant factors

A

flower regardless of day length

e.g. roses, dandelions, tomatoes

116
Q

phytocromes

A

pigment containing proteins; play an important role in plant regulation as they change back and forth between two isomeric forms

  • they activate or inhibit gene transcription of flowering
117
Q

Pr

A

absrobs red light and converts it to infrared during the daytime

118
Q

PFr

A

absorbs infrared light and converts it to red light during the night time
e.g. sedd inhibited by infrared but promoted by red light

119
Q

when do long day plants bloom?

A
  • when nights are short
  • less Pfr levels found and high Pr (Pr converted to PFr)
  • high PFr binds to a protein which acts as a trancription factor switching on the gene for flowering
120
Q

why wouldnt a short day plant bloom?

A
  • high Pfr levels= inhibit flowering
121
Q

example of short day plant

A

chrystanthemums; botanists will place a cloth over this flower over certain period of time to cause plant to flower

IB BIOLOGY 2017 EXAM (11 decks)

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