271 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 ID: 935453
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Slide1
IB Biology III
Chapter 27:Plant tissues
Slide227.1: 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.
Slide3Slide427.2: 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.
Slide5Slide627.3: 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
.
Slide7Slide8Slide9Slide10Slide11Slide12Slide1327.4: 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.
Slide14Slide15Slide16Slide17Slide18Slide19Slide20Slide2127.5: 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.
Slide22Slide2327.6: 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.
Slide24Slide25Slide26Slide2727.7: 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.
Slide28Slide29Slide30Slide3127.8: 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.
Slide32Slide33Slide34Slide3527.9: 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.
Slide36Slide37Slide38Slide39Slide40IB Biology III
Chapter 28:plant nutrition and transport
Slide4128.1: 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.
Slide42Zombies!!!!!!!!!!!!!!
Slide43Slide4428.2: 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
.
Slide45Ugh!
Slide46Slide47Slide48Slide4928.3: 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.
Slide50Slide51Most 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.
Slide5228.4: 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.
Slide53Slide54Slide5528.5: 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.
Slide56Slide5728.6: 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.
Slide581.
2.
3.
4.
Slide59IB Biology III
Chapter 29:life cycles of flowing plants
Slide6029.1: 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.
Slide6129.2: 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.
Slide62Slide6329.3: 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.
Slide64Slide6529.4: 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
.
Slide66Slide67Take 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.
Slide6829.6: 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.
Slide69Slide7029.7: 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.
Slide71Slide7229.8: 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.
Slide73Slide74Slide7529.9: 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.
Slide76IB Biology III
Chapter 30:communication strategies in plants
Slide7730.1: 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.
Slide7830.2: 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.
Slide7930.3: 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.
Slide8030.4: 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.
Slide8130.5: 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.
Slide8230.6: 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.
Slide8330.7: 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.
Slide8430.8: 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.
Slide8530.9: 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
).
Slide8630.10: 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.
Slide87IB Biology III
Chapter 9:Plant biology
Slide889.1: 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.
Slide899.2 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.
Slide909.3: 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.
Slide919.4: 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.