Plants basic
Transcript of Plants basic
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Plant Ancestry 1
Red Algae phycoerythrin pigment
- deep water, most are unicellular
- many use alternation of
generations (a multicellular
diploid sporophyte and a haploidgametophyte
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Green Algae similar ultrastructure to plants
Chlorophytes (phylum name)
Unicellular flagellatedEx: chlamydomonas
see life cycle p. 567
Colonial
Ex: spyrogyra and volvox
Multicellular
Ex: ulva and caulerpa
(see life cycle)
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Green Algae Charophyceans (phylum)
- similar cellulose production mechanism
- similar peroxisome enzyme- similar flagellated sperm structure
- genetic similarities
- similar phragmoplast formation (vesiclesand cytoskeleton complex near the cell
plate during mitosis)
- both have sporopollenin, a polymer thatprevents exposed zygotes from drying
out
Stop and show PLOP
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Plants 2
They are distinguished from algae becausethey are embryophytes (plants with embryos)
Land plants have: (charophyceans dont)
see p. 576- Apical meristems found at the tips of
roots and shoots; a dividing region of
nondifferentiated cells.
- Alternation of generations - alternate
between adult haploid gametophyte
and adult diploid - sporophyte
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- Walled spores produced in sporangia
adult sporophyte has a structure called
sporangia which produces haploid sporesfrom a diploid sporocyte. Spores are
walled in sporopollenin.
- Multicellular gametangia that producegametes.
Female version: archegonia produces
1 egg.Male version: antheridia produces
sperm, many are flagellated
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- Multicellular, dependent embryos
Embryos develop inside the female parent,
receives nourishment from placentaltransfer cells. Therefore, known as
embryophytes.
- Also, many plants have a waxy cuticle to
prevent dessication (drying out) and pathogen
infection.- Many have special metabolic pathways to
produce secondary compounds to deter
predators,block uV light, etc.
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Plant divisions 3
Nonvascular (a.k.a. Bryophytes)- No extensive transport system
- Includes mosses, liverworts and
hornworts
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Nonvascular Plants (Bryophytes) Mosses
- Many live in moist environments (b/c
no vascular tissue.- mosses and liverworts have stomata
- sphagnum moss produces peat (partially
decayed organic matter)- have rhizoids; long filaments of cells to
anchor the moss, no role in water or
mineral absorption, not made of tissue.
- Life cycle see diagram on page 581
alternation of generations
(know all terms)
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Vascular Plants (a.k.a. Tracheophytes)
- 2 groups:
Seedless Plants
- club and spike mosses- ferns
Seed Plants: embryos are packaged with
a supply of nutrients in a protective coat.2 types:
GymnospermsNaked seed plants, no
chambers for a seed (mostly conifers).AngiospermsFlowering plants, seeds
develop in ovaries/chambers. Ovary
originates as flowers and develop into
fruits.
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Vascular Plants (Tracheophytes) 4
Evolved in the early Carboniforous. Most
early plants (bryophytes and ferns) werelimited to moist environments by
swimming sperm.
All vascular plants have:
1. Life cycles with a dominant (large and
complex) sporophyte, gametophyte
is very reduced.2. Roots that are present to anchor the
plant and absorb nutrients and water.
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3. Transport using vascular tissues
known as xylem and phloem.
xylem conducts most water andminerals.
- includes tracheids (dead,
tube-shaped cells)
- cells are strengthened by
lignin (protein allows them
to grow tall.)
phloem living, sugar-conductingcells arranged in tubes
- distribute sugars, amino
acids, and organic products.
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4.Leaves are present to increase surface
area for photosynthesis.
2 main types of leaves:Microphylls small, spine-shaped
with a single vein
Megaphylls highly branched, largerhave a vascular system
(p. 586)
There are also some spore-bearing
leaves called sporophylls.
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microphyll megaphyll
http://en.wikipedia.org/wiki/File:Illustration_Isoetes_lacustris0.jpg -
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Seedless Vascular Plants 5
Ferns! See fern life cycle on p. 585
(alternation of generations)Seed Vascular Plants
- Have a microscopic gametophyte (thats
so cute!) It stays inside the femalesporophyte for protection.
- Most plants have 2 kinds of spores (p. 593)
Megasporangia produces a megaspore
which develops into female gametophyt
Microsporangia produces a microspore
which develops into male gametophyte
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-Have Ovules (female) which consist of
megasporangium, a megaspore and
sporophyte tissue called integument.
-Have Pollen grains (male) which develop
from microspores and contain the male
gametophyte protected by sporopollenin.
-Pollenation occurs when pollen is
transferred to the ovule. Pollen grains land,germinate, and grow a pollen tube that
delivers the male gametophyte.
Most sperm are nonflagellated.
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- The fertilized ovule will develop into a seed.
The seed contains: embryo, food and a
protective seed coating called the integument
- The seed resists hash environments by
lying dormant.- Seeds increase dispersal rate for
offspring.
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Gymnosperms: naked seeds (not in ovary)
-Many seeds are exposed on modified
leaves (usually from cones). Therefore,
they are known as conifers.
- Life cycle see p. 597
Figure 30 6 4
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Key
Haploid (n)
Diploid (2n)
Maturesporophyte(2n)
Ovulatecone
Pollencone
Microsporocytes(2n)
MicrosporangiaMicrosporangium (2n)
Seedling
Archegonium
Survivingmegaspore (n)
MEIOSIS
Megasporangium (2n)Pollengrain
Pollengrains (n)
MEIOSIS
Femalegametophyte
Megasporocyte (2n)
Integument
Spermnucleus (n) Egg nucleus (n)
Pollentube
Seed coat (2n)
FERTILIZATION
Foodreserves (n)
Seeds
Embryo(new sporophyte)
(2n)
Ovule
Figure 30.6-4
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Angiosperms (Phylum Anthophyta): 6
Flowering Plants:
- Flowers are specialized for sexual reproduc.- Pollination occurs with the help of wind (like
gymnosperms), insects, etc. (more directed.)
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Flower Anatomy see p. 598
sepals and petals sepal protects flowers.- petals attract pollinators.
stamens (microsporophylls) produce
male microspores that make pollengrains containing a male gametophyte.
parts: filament (stalk) and
anther (terminal sac, pollen isproduced there)
.
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Carpels (megasporophylls) make
megaspores that become
gametophytes.
Sometimes, 1 carpel or group of
carpels is called the pistil.
parts: stigma sticky tip that receivespollen.
style leads to the ovary
ovary at base of carpel, hasone or more ovules.
receptacle attaches carpel
to stem.
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Fruits they are thick ovaries at maturity
(Ex: pea pod, see p. 599)
- they protect seeds and aid in dispersal- pollination triggers a hormone change
that causes the ovary walls to thicken
and become pericarp.- Fleshy pericarp: peaches, apples
- Dry pericarp: nuts, beans, grains
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Life Cycle of an Angiosperm see p. 772
- Most species cross pollinate (p. 600)
- Double pollination occurs in most:
1. Diploid zygote is formed from
one fertilized egg.
The sporophyte embryo
develops with a rudimentaryroot and one or two seed leaves.
(monocots one, dicots two)
2. Second sperm fuses with 2 nucleiin the central cell of the (polar)
gametophyte. Forms a cotyledon
with starch and amino acids for
nourishment. See . 603.
Figure 30.10-4
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AntherMature flower onsporophyte plant(2n)
Germinatingseed
Megasporangium (2n)
Ovary
Embryo (2n)
Endosperm (3n)
Seed coat (2n)
Seed
Antipodal cells
Central cell
Synergids
Femalegametophyte
(embryo sac)Egg (n)
Eggnucleus (n)
Survivingmegaspore(n)
Pollentube
Sperm(n)
Style
SpermPollentube
Stigma
Pollengrains
Tube cell
Generative cell
Microspore (n)
Malegametophyte
(in pollengrain) (n)
Ovule (2n)
MEIOSIS
MEIOSIS
Discharged sperm nuclei (n)
FERTILIZATIONZygote (2n)
Microsporangium
Microsporocytes (2n)
Nucleus of
developingendosperm(3n)
Key
Haploid (n)
Diploid (2n)
Figure 30.10 4
Figure 30.3-3
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g
Immature
ovulate cone
Integument (2n)
Spore wall
Megaspore (n)
Female
gametophyte (n)
Egg nucleus
(n)
Dischargedsperm nucleus(n)
Pollen tubeMale gametophyte (n)
(a) Unfertilized ovule
Megasporangium
(2n)
Pollen grain (n)Micropyle
(b) Fertilized ovule (c) Gymnosperm seed
Seedcoat
Sporewall
Foodsupply (n)
Embryo (2n)
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Chapter 36 Transport in Plants 3 Types 7
See p. 739
1.Individual Cell Transport of water andsolutes.
Proton Pumps p. 739 and 740. Builds
up a membrane potential outsideof the cell (uses ATP). Cotransport
through chemiosmosis transports
substances back into the cell.
Ex: sugar (sucrose) loading from leaves
K+, NO3- from root cells
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-Hydrogen Ions play primary role in basic
transport processes
-During cotransport, plant cells use
energy in H+ gradient and membrane
potential to drive AT of different solutes
-Facilitates movement of ion-Ion Channels
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-Root Hairs on a root cell help to increase
surface area.
-Roots and the hyphae of soil fungi formmutualistic association called mycorrhizae
-Mycorrhizal fungi increase the surface area for
absorbing water and minerals, especiallyPhosphate
Some plants have a symbiosis with
Mycorrhizae (p. 745), which are fungal
Hyphae that absorb water and minerals
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2. Short Distance Transport between
several cells. (water and solute transport
at the tissue and organ level)3 Pathways (p. 743)
1 Can pass through each cell membrane
(through aquaporins and proteins)2 Pass through Symplast, which is a
cytosol continuum of plasmodesmata
3 Pass through Apoplast, which is a
continuum of cell walls andextracellular spaces (very direct route)
Figure 36.6
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gu e 36 6
Cell Cell Wallwall
Cytosol
Plasmodesma
Plasma membrane
Apoplastic route
Symplastic route
Transmembrane route
Key
Apoplast
Symplast
3 Long Distance Transport (xylem and phloem)
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3. Long Distance Transport (xylem and phloem)
Xylem unidirectional transport from
roots to leaves. P. 748
Increases water loss because oftranspiration through stomata (90%
is lost can wilt if not replaced)
Water and minerals that pass from the soil into
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Water and minerals that pass from the soil into
the root cortex cannot be transported to the rest
of the plant until they enter the xylem of the
vascular cylinder, or stele. The endodermis, the innermost layer of cells in
the root cortex, surrounds the stele and
regulates the selective passage of minerals from
the cortex into the stele.
Minerals already in the symplast when they
reach the endodermis continue through the
plasmodesmata of endodermal cells and passinto the stele.
These minerals already crossed a plasma
membrane to enter the symplast in the
epidermis or cortex.
The endodermis with its Casparian strip
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The endodermis, with its Casparian strip,
ensures that no minerals can reach the vascular
tissue of the root without crossing a selectively
permeable plasma membrane. The Casparian strip, located in the transverse
and radial walls of each endodermal cell, is a
belt made of suberin, a waxy material
impervious to water and dissolved minerals.
The Casparian strip prevents water and minerals
from crossing the endodermis and entering the
vascular tissue via the apoplast. Water and minerals that are passively moving
through the apoplast must cross the plasma
membrane of an endodermal cell and enter the
stele via the symplast.
The endodermis also prevents solutes that have
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The endodermis also prevents solutes that have
accumulated in the xylem from leaking back into
the soil solution.
Tracheids and vessel elements of the xylem lackprotoplasts when mature and are parts of the
apoplast.
Endodermal cells and living cells within the
vascular cylinder discharge minerals from their
protoplasts into their own cell walls.
Both diffusion and active transport are involved
in the transfer of solutes from symplast toapoplast.
Water and minerals enter the tracheids and
vessel elements, where they are transported to
the shoot system by bulk flow.
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Xylem Loading water and mineral
absorption pathway to xylem: p. 745
Epidermis (via root hairs)
to cortex (made of ground tissue)
to endodermis via symplast(waxy Casparian Strip forces water
to go through a membrane to
prevent minerals and water fromleaking out.)
To xylem
EpidermisFigure 35.14
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Epidermis
Cortex
Endodermis
Vascularcylinder
Pericycle
Core ofparenchymacells
Xylem
Phloem
Endodermis
Pericycle
Xylem
Phloem
Dermal
Ground
Vascular
Keyto labels
50 m
100 m100 m
(a)(b) Root with parenchyma in the
center (typical of monocots)
Root with xylem andphloem in the center(typical of eudicots)
Casparian stripFigure 36.10
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Pathway alongapoplast
Casparian strip
Endodermalcell
Pathwaythroughsymplast
Plasma
membrane Casparian strip
Apoplasticroute
Symplasticroute
Roothair
Epidermis Endodermis
Vessels(xylem)
Vascular cylinder(stele)
Cortex
X l T
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Xylem Transport:
- At night, roots pump minerals into the
xylem. This decreases the water
potential inside, forcing water to diffuse
in from the cortex. This generates
root pressure, an upward push of xylem
sap. If too much water flows in,guttation results at the leaves.
- Transpiration results in an upward pull
from: adhesion, cohesion, surfacetension and negative pressure at
the water/air interface, negative
water potential at leaves.
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Phloem: transfers organic nutrients 8
known as translocation.- In angiosperms, sucrose is transferred
from mesophyll cells to phloem by
specialized phloem cells called
seive-tube members.- Phloem sap can be up to 30% sucrose.
(& some amino acids, minerals,
hormones)
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- Direction of transport is variable, but is
always from a sugar source to a sugar
sink.Source organ that produces
sugar or breaks down starch
Sink a net consumer or storer ofsugar (growing roots, buds,
stems and fruits)
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Loading of Phloem see p. 752
Mesophyll cells symplast or apoplast
sometimes via companion cells(with ingrowth of cell walls) known as
transfer cells seive tube members
of phloem.
Loading into companion cells is usually
done through active transport via proton
pump and cotransport. (This is because
seive tube sucrose content is 2-3 times
higher than mesophyll.)
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- Unloading of phloem is usually done through
diffusion at a sugar sink.
-Movement through phloem occurs through
pressure flow of sugar solution (p. 753)
Increased pressure builds up at thesource. Lower pressure is at the sink.
This causes the xylem water to diffuse
into the phloem and move from sourceto sink and take sucrose with it
(rate is about 1m/hour.)
Figure 36.18
Sieve
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Loading of sugar
Uptake of water
Unloading of sugar
Water recycled
Source cell(leaf)
Vessel(xylem)
Sievetube
(phloem)
SucroseH2O
H2O
H2OSucrose
Sink cell(storage
root)Bulkflowb
ynegativ
epressure
Bulkflowb
yposit
ivepressure
2
1
3
4
2
1
34
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Ch. 35 Plant Structure, Growth and Develop.
Growth:
Annuals complete their life cyclesin 1 year or less
Bienniels live 2 years
Perenniels live many years (trees,shrubs, some grasses)
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Plant tissues:
Dermal (epidermis, endoderm)
- single layer of tightly packed cellsto cover and protect
Ex: root hairs, cuticle
Vascular (transport tissues)
Ground Tissue bulk of plant tissue is
ground tissue which is found
between the dermis and vascular
tissues. Mostly made ofparenchyma cells. Functions in
photosynthesis, storage, support,
and metabolism.
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Specialized Cells:
Parenchyma Cells thin, flexible (no
secondary cell wall), most commontype, can divide for repair.
Found in: photosynthetic cells,
stems, roots, fruits, and usuallyhave plastids.
Collenchyma cells grouped in strands,
help support young shoots.
No secondary cell wall (no lignin);
therefore, they can grow.
Ex: celery strings
Figure 35.10a
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Parenchyma cells in Elodealeaf, with chloroplasts (LM)
60 m
Figure 35.10b
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Collenchyma cells(in Helianthusstem) (LM)
5 m
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Sclerenchyma Cells supporting cells
with thick secondary cell walls with
lignin. Cannot elongate whenmature. Many are dead at
maturity (lose protoplasts.)
2 types:sclereids short and irregular
shaped, like in seed coats,
nut shells or pear grit.fibers fibers that are long, thin,
and tapered like hemp or
flax.
Figure 35.10c
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Cell wall
Sclereid cells in pear (LM)
Fiber cells (cross section from ash tree) (LM)
25 m
5 m
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More Plant Growth:
Apical Meristems tips of roots and
buds of shoots.- Responsible for increase in
length, primary growth.
(lateral meristems help withsecondary growth, increase in
width: vascular tissue and cork
cambium)
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See p. 721 (bottom) for apical meristem
Root cap for protection
Zone of Division includes root apical
meristem. New cells produced
here (mitotic division.)
Zone of Elongation cells elongate,push tip
Zone of Maturation cells complete
differentiation and mature.This produces epidermis, ground
tissue and vascular tissue.
Figure 35.13Cortex Vascular cylinder
Key
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Epidermis
Root hair
Zone of
differentiation
Zone ofelongation
Zone of celldivision(includingapicalmeristem)
Keyto labels
Root cap
Dermal
Ground
Vascular
Mitoticcells
100 m
Tissue organization of stems and roots:
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Tissue organization of stems and roots:
(on your own) p. 724 and lab manual
(p. 106)
Tissue organization of leaves see p. 725
cuticle
upper epidermis
palisade meophyll (tighter)spongy mesophyll spread out
(increases gas exchange)
veins (xylem and phloem) covered withbundle sheath cells for protection
lower epidermis
cuticle
Figure 35.18a
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Keyto labels
Dermal
GroundVascular
Cuticle
Bundle-sheathcell
Xylem
Phloem
Sclerenchymafibers
Stoma
Upperepidermis
Palisademesophyll
Spongymesophyll
Lower
epidermis
CuticleVein
Guardcells
(a) Cutaway drawing of leaf tissues
Figure 36.12
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CuticleUpperepidermis
Mesophyll
Lower
epidermis
Cuticle
Xylem
Airspace
Microfibrils incell wall ofmesophyll cell
Microfibril(cross section)
Waterfilm
Air-waterinterface
Stoma
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Plant Hormones
see p. 794