plants basic

7/27/2019 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

plants basic

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