IB Biology III Chapter 27:Plant tissues - PowerPoint Presentation

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IB Biology III

Chapter 27:Plant tissues

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27.1: carbon sequestration

By the process of photosynthesis, plants naturally remove carbon from the

a

tmosphere and incorporate it into their tissues. Carbon that is locked in

m

olecules of wood and other durable plant tissues can stay out of the

a

tmosphere for centuries.

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27.2: The plant body

Most flowing plants have belowground roots and aboveground shoots,

i

ncluding stems, leaves, and flowers.

Ground tissue

makes up the bulk of a

p

lant, and

dermal tissues

protect its surfaces.

Vascular tissues

conduct

w

ater and nutrients to all parts of the plant. Monocots and eudicots have

t

he same tissues organized in different ways. For example, embryos of

m

onocots have one

cotyledon

, those of eudicots have two.

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27.3: plant tissues

Parenchyma

,

collenchyma

, and

sclerenchyma

are simple tissues; each

c

onsists of only one type of cell.

Mesophyll

is photosynthetic parenchyma.

Living cells in collenchyma have sturdy, flexible walls that support fast-

g

rowing plant parts. Cells in sclerenchyma die at maturity, but their

ligin

-

r

einforced walls remain and support the plant. Stomata open across

e

pidermis

, a dermal tissue that covers soft plant parts. In vascular tissue,

w

ater and dissolved minerals flow through vessels in

xylem

, and sugars

t

ravel through vessels of

phloem

.

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27.4: stems

Vascular bundles

extending through stems conduct water and nutrients

b

etween different parts of the plant, and also helps structurally support the

p

lant body. In most eudicot stems, vascular bundles form a ring that

d

ivides the ground tissue into cortex and pith. In monocot stems, the

v

ascular bundles are distributed throughout the ground tissue. New

s

hoots and roots form at

nodes

on stems. Stem specializations such as

r

hizomes, corms, stem tubers, bulbs, cladodes, and

stolons

are

a

daptations for storage or reproduction in many types of plants.

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27.5: leaves

Leaves, which are specialized for photosynthesis, contain mesophyll and

v

ascular bundles (

leaf veins

) between upper and lower epidermis. Eudicots

t

ypically have two layers of

meosphyll

; monocots do not. Water vapors

and gases cross cuticle-covered epidermis at stomata.

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27.6: roots

Roots absorb water and mineral ions for the entire plant. Inside each is a

v

ascular cylinder (stele)

. The outer boundary of the vascular cylinder is a

l

ayer of

endodermis

.

Root hairs

increase the surface area of roots. Many

m

onocots have a

fibrous root system

that consists of similar-sized

a

dventitious roots. Most eudicots have a

taproot system

– an enlarged

p

rimary root with its lateral root

branchings

. Lateral roots arise from

d

ivisions of

pericycle

cells inside the root vascular cylinder.

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27.7: primary growth

All plant tissues originate at

meristems

, which are regions of

undifferentiated cells that retain their ability to divide.

Primary growth

(lengthening) arises at

apical meristems

in

terminal buds

and

lateral buds

i

n the tips of shoots and roots.

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27.8: secondary growth

Secondary growth

(thickening) arises at

lateral meristems

(

vascular

c

ambium

and

cork cambium

) in older stems and roots. Vascular cambium

p

roduces secondary xylem (

wood

) on its inner surface, and secondary

p

hloem on its outer surface. Cork cambium gives rise to

cork

, which is

p

art of

periderm

.

Bark

is all tissue outside of the vascular cambium of a

w

oody plant.

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27.9: tree rings and old secrets

In many trees, one ring forms during each growing season. Tree rings

h

old information about environmental conditions that prevailed while the

r

ings were forming. For example, the relative thicknesses of the rings

r

eflect the relative availability of water.

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IB Biology III

Chapter 28:plant nutrition and transport

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28.1: leafy cleanup

The ability of plants to take up substances from soil water is the basis for

p

hytoremediation, which is a method that uses plants to remove pollutants

f

rom a contaminated area.

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Zombies!!!!!!!!!!!!!!

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28.2: plant nutrients and availability in soil

Plant growth requires steady sources of elemental nutrients. Oxygen,

c

arbon, and hydrogen atoms are abundant in air and water; nitrogen,

p

hosphorus, sulfur, and other elements are available in soil. The

a

vailability of water and mineral ions in a particular soil depends on its

p

roportions of sand, silt, and clay, and also on its

humus

content.

Loams

h

ave roughly equal proportions of sand, silt, and clay.

Leaching

and

soil

e

rosion

deplete nutrients from soil, particularly

topsoils

.

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Ugh!

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28.3: root adaptations for nutrient uptake

Transport proteins in root cell plasma membranes control the plant’s

u

ptake of substances in soil water. Endodermal cells that form the

v

ascular cylinder’s outer layer deposit a

Casparian

strip into their abutting

w

alls. This waxy, waterproof band prevents soil water from diffusing

a

round endodermal cells into root xylem. Substances such as ions in soil

w

ater must pass through membrane transport proteins of an endodermal

c

ell (or other root cell). Once in cytoplasm, the ions can diffuse through

p

lasmodesmata

to

pericycle

cells, which load them into xylem. Many

p

lants form mutualisms with microorganisms. Fungi associate with young

r

oots in mycorrhizae, which enhance the plant’s ability to absorb mineral

i

ons from soil. Nitrogen fixation by bacteria in

root nodules

gives a plant extra

n

itrogen. In both cases, the microorganisms receive some sugars made by the

p

lant.

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Most flowering plants take part in mycorrhizae and

other mutualisms that provide nutritional benefit.

A mycorrhiza is a mutually beneficial interaction

between a root and a fungus that grows on or in it.

Filaments of the fungus (hyphae) form a velvety

cloak around roots or penetrate their cells. Collectively,

the hyphae have a large surface area, so they absorb

mineral ions from a larger volume of soil than roots

alone. In return, the root cells get some scarce minerals

that the fungus is better able to absorb.

Some plant species form mutualisms with nitrogen-fixing

Rhizobium

bacteria. The plants require a lot of nitrogen,

but cannot use nitrogen gas that is abundant in air. The

bacteria in the root nodules fix this gas to ammonia,

which is a form of nitrogen that the plant can use. In

return for this valuable nutrient, the plant provides an

oxygen-free environment for the anaerobic bacteria, and

shares its photosynthetically produced sugars with them.

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28.4: water movement inside plants

Water and dissolved mineral ions flow through xylem from roots to shoot

t

ips. Xylem tubes consist of stacks of dead cells:

tracheids

and

vessel

e

lements

. Water moves through the perforated and lignin-reinforced

s

econdary walls of these cells. The

cohesion-tension theory

explains how

w

ater moves upward through xylem:

Transpiration

(the evaporation from

a

boveground plant parts, mainly at stomata) pulls water upward. This pull

(tension) extends from leaves to roots because of water’s cohesion inside

t

he narrow tubes of xylem. Cohesion also keeps the water from breaking

i

nto droplets, so it moves upward in continuous columns.

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28.5: water-conserving adaptations of stems and leaves

A cuticle helps a plant conserve water; stomata help it balance water

c

onservation with gas exchange required for metabolism. A stoma, which

i

s a gap between two

guard cells

, may be surrounded by an indentation,

p

rotrusions, or other specializations that reduce airflow around it.

Environmental and internal signals cause stomata to open or close. The

s

ignals trigger guard cells to pump ions into or out of their cytoplasm;

w

ater follows the ions by osmosis. Water moving into guard cells plumps

t

hem, which opens the stoma between them. Water diffusing out of the

c

ells causes them to collapse against each other, so the stoma closes.

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28.6: movement of organic compounds in plants

Sugars move through a plant by

translocation

in phloem’s

sieve tubes

,

w

hich consist of stacked

sieve elements

separated by perforated sieve

p

lates. By the

pressure flow theory

, the movement of sugar-rich fluid

t

hrough a sieve tube is driven by a pressure gradient between

source

and

sink

.

Companion cells

load sugars into sieve elements at sources.

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1.

2.

3.

4.

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IB Biology III

Chapter 29:life cycles of flowing plants

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29.1: plight of the honeybee

Colony collapse disorder (CCD) is killing honeybees. Declines in

p

opulations of bees and other

pollinators

negatively affect plant

p

opulations as well as other animal species that depend on the plants,

i

ncluding humans. Widely used neonicotinoid pesticides may contribute

t

o CCD.

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29.2: reproductive structures

Flowers

consist of whorls of modified leaves at the ends of specialized

b

ranches of angiosperms. A

calyx

of

sepals

surrounds a

corolla

of

petals

,

w

hich in turn surround

stamens

and

carpels

. A carpel consists of a

s

tigma

, often a style, and an

ovary

inside which one or more

ovules

d

evelop. The female gametophyte forms inside an ovule. A stamen

c

onsists of an

anther

on a thin filament. Anthers produce pollen grains.

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29.3: Flowers and their pollinators

Pollination

is the arrival of pollen on a receptive stigma. A flower’s shape,

p

attern, color, and fragrance typically reflect an evolutionary relationship

w

ith a particular

pollination vector

, often a coevolved animal. Coevolved

p

ollinators receive

nectar

, pollen, or another reward for visiting a flower.

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29.4: a new generation begins

29.5: Flower sex

Meiosis of diploid cells inside pollen sacs of anthers produces haploid

m

icrospores

. Each microspore develops into a pollen grain that is released

f

rom a pollen sac after a period of

dormancy

. Meiosis and cytoplasmic

d

ivision of a cell in an ovule produce four

megaspores

, one of which gives

r

ise to the female gametophyte. One of the seven cells of the

g

ametophyte is the egg; another is the endosperm mother cell. An

i

nterplay of species-specific molecular signals trigger a pollen grain to

germinate

on a receptive stigma and form a pollen tube that contains two

s

perm cells. Other molecular signals guide pollen tube growth through

t

issues of the carpal to the egg. In

double fertilization

, one of the sperm

c

ells in the pollen tube fertilizes the egg, forming a zygote; the other fuses

w

ith the endosperm mother cell and gives rise to triploid

endosperm

.

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Take home message:

A pollen grain that germinates on a stigma develops into the male gametophyte,

which consists of a pollen tube and two sperm cells. The pollen tube grows into

the carpel, enters the ovule, and releases the sperm cells.

Double fertilization occurs when one of the sperm cells delivered by the pollen

tube fuses with the egg, and the other fuses with the endosperm mother cell.

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29.6: seed formation

As a zygote develops into an embryo, endosperm collects nutrients from

t

he parent plant, and the ovule’s protective layers develop into a seed

c

oat. A

seed

is a mature ovule: an embryo sporophyte and endosperm

e

nclosed within a seed coat. Nutrients in endosperm or cotyledons make

s

eeds a nutritious food source.

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29.7: fruits

As an embryo sporophyte develops, the ovary wall and sometimes other

t

issues mature into a

fruit

that encloses the seeds. Fruit specializations

a

re adaptations to seed dispersal by specific vectors such as wind, water,

o

r animals. A fruit can be categorized by tissue of origin, composition,

a

nd whether it is dry or fleshy.

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29.8: early development

Seeds often undergo a period of dormancy that does not end until

s

pecies-specific environmental cues trigger germination. The radicle

e

merges from the seed coat at the end of germination; other patterns of

e

arly development vary. For example, monocot

plumules

are sheathed

b

y a

coleoptile

; eudicot hypocotyls form a hook that pulls cotyledons up

t

hrough soil.

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29.9: Asexual reproduction of flowing plants

Many types of flowering plants produce clonal offspring by

vegetative

r

eproduction

. Some are propagated commercially by grafting; the

c

ommon laboratory technique of

tissue culture propagation

is used to

p

ropagate some valuable ornamentals.

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IB Biology III

Chapter 30:communication strategies in plants

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30.1: Prescription: chocolate

Secondary metabolites are not required for immediate survival of the

o

rganism that produces them. Some plant secondary metabolites attract

p

ollinators or symbionts, or function in defense. A few of these

c

ompounds, including a number of flavonoids, are beneficial to human

h

ealth.

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30.2: introduction to plant hormones

Plants continue to develop through their lifetime.

Plant hormones

p

romote or arrest development in regions of a plant by stimulating or

i

nhibiting cell division, differentiation, or enlargement. Some have roles

i

n occasional responses such as pathogen defense. Hormones work

t

ogether or in opposition, and many have different effects in different

r

egions of the plant.

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30.3: auxin: the master growth hormone

Auxin

promotes lengthening and also coordinates the effects of other

h

ormones involved in growth. A unique transport system distributes

a

uxin directionally. The polar distribution sets up auxin gradients that

a

ffect the growth and development of plant parts, such as when auxin

g

radients maintain

apical dominance

in a growing shoot tip.

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30.4: cytokinin

Cytokinin

promotes cell division in shoot apical meristem, and

d

ifferentiation in root apical meristem. This hormone acts together with

a

uxin, often antagonistically, to balance growth with development in

s

hoot and root tips.

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30.5: Gibberellin

Gibberellin

lengthens stems between nodes by inducing cell division and

e

longation. It also stimulates production of enzymes that break down

e

ndosperm during seed germination.

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30.6: abscisic acid

Abscisic acid (ABA)

plays a part in

abscission

, but has a greater role in

o

ther processes, especially responses to stress. ABA influences

e

xpression of thousands of genes, with effects that include the

s

uppression of seed germination, and growth. ABA also participates in

e

mbryonic development and fruit ripening.

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30.7: ethylene

Ethylene

is produced in negative and positive feedback loops. The

negative feedback loops help regulate ongoing metabolism and

d

evelopment; the positive feedback loops trigger special processes such

a

s abscission, ripening, and defense responses.

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30.8: tropisms

A

tropism

is an adjustment in the direction of plant growth in response to

environmental cues such as gravity (

gravitrophism

), light (

phototropism

),

o

r contact (

thigmotropism

).

Statoliths

play a part in gravitropism.

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30.9: sensing recurring environmental change

Circadian rhythms

are driven by gene expression feedback loops that

h

ave input from

nonphotosynthetic

pigments such as

phytochromes

.

P

hotoperiodism

is a response to change in the length of day relative to

n

ight. Seasonal cycles of abscission and dormancy are adaptations to

s

easonal changes in environmental conditions. Some plants require

p

rolonged exposure to cold before they can flower (

vernalization

).

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30.10: responses to stress

Plants use hormones to respond to abiotic and biotic stresses. ABA is

p

art of the stress response that closes stomata when water is scare.

N

itric oxide is part of a hypersensitive defense response that closes

s

tomata or kills the cell in response to pathogen detection. Pathogen-

t

riggered

systemic acquired resistance

increases the plant’s resilience

t

o biotic and abiotic stress in genera.

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IB Biology III

Chapter 9:Plant biology

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9.1: transport in the xylem of plants

Plants are highly diverse in structure and physiology. They act as the

p

roducers in almost all terrestrial ecosystems. Structures and function

a

re correlated in the xylem and phloem of plants. Plants have

s

ophisticated methods of adapting their growth to environmental

c

onditions. Reproduction in flowering plants is influenced by both the

b

iotic and abiotic environment.

Transpiration is the inevitable consequence of gas exchange in the leaf.

Plants transport water from the roots to the leaves to replace losses

from transpiration.

The cohesive property of water and the structure of the xylem vessels

allow transport under tension.

The adhesive property of water and evaporation generate tension forces in

leaf cell walls.

Active uptake of mineral ions in the roots causes absorption of water by osmosis.

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9.2 transport in the phloem of plants

Plants transport organic compounds from sources to sinks.

Incompressibility of water allows transport by hydrostatic pressure

gradients.

Active transport is used to load organic compounds into phloem sieve

tubes at the source.

High concentrations of solutes in the phloem at the source lead to water

uptake by osmosis.

Raised hydrostatic pressure causes the contents of the phloem to flow

toward sinks.

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9.3: Growth in plants

Undifferentiated cells in the meristems of plants allow indeterminate

growth.

Mitosis and cell division in the shoot apex provide cells needed for

extension of the stem and development of leaves.

Plant hormones control growth in the shoot apex.

Plants respond to the environment by tropisms.

Auxin influences cell growth rates by changing the pattern of gene

expression.

Auxin efflux pumps can set up concentration gradients of auxin in plant

tissues.

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9.4: Reproduction in plants

Flowering involves a change in gene expression in the shoot apex.

The switch to flowering is a response to the length of light and dark

periods in many plants.

Most flowering plants use mutualistic relationships with pollinators

in sexual reproduction.

Success in plant reproduction depends on pollination, fertilization and

seed dispersal.