2006-2007 Plant Anatomy Basic plant anatomy 1 - PowerPoint Presentation

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2006-2007

Plant Anatomy

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Basic plant anatomy 1

rootroot tiproot hairs

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Roots Roots anchor plant in soil, absorb minerals & water, & store foodfibrous roots (1)mat of thin roots that spread outmonocotstap roots (2)

1 large vertical root also produces many small lateral, or branch roots dicotsroot hairs (3)increase absorptive

surface area

2

1

3

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Basic plant anatomy 2

rootfungi at tips of the roots Mycorrhizae-Symbiotic relationshipshoot (stem)

budsterminal or apical buds-located at the topaxillary buds-located at the V formed b/t leaf and stem

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Modified shootsstolons (strawberries)

rhizome (ginger)

tuber (potato)

bulb (onion)

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LeavesFunction of leavesphotosynthesisenergy productionCHO productiongas exchangetranspiration

simple vs. compound

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Putting it all together Obtaining raw materialssunlightleaves = solar collectorsCO2stomates = gas exchange

H2Ouptake from rootsnutrients

uptake from roots

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Plant TISSUESDermalepidermis (“skin” of plant)single layer of tightly packed cells that covers & protects plant

Groundbulk of plant tissue photosynthetic mesophyll, storage

Vasculartransport system in shoots & roots xylem & phloem

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Plant CELL types in plant tissuesParenchyma“typical” plant cells = least specializedphotosynthetic cells, storage cellstissue of leaves, stem, fruit, storage rootsCollenchymaunevenly thickened primary wallssupportSclerenchyma very thick, “woody” secondary wallssupport

rigid cells that can’t elongatedead at functional maturity

If I

’d only

had triplets

!

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Xylem and PhloemXylem- water conducting cells. xylem vessels- found mostly in angiosperms have pits for water movement. xylem tracheids- long thin cells strengthen with lignin

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tracheids

vessel elements

Vascular tissue

Aaaah

…

Structure

–

Function

again

!

vessel

element

dead cells

Xylem

move

water & minerals

up from roots

dead

cells at functional maturity

only cell walls remain

need empty pipes to efficiently move H

2

O

transpirational pull

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Phloem: food-conducting cellscarry sugars & nutrients throughout plant

sieve tube

companion cell

living cells

plasmodesmata

sieve plate

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Phloem: food-conducting cellssieve tube elements & companion cells

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PhloemLiving cells at functional maturitycell membrane, cytoplasmcontrol of diffusionlose their nucleus, ribosomes & vacuolemore room for specialized transport of liquid food (sucrose)Cells sieve tubessieve plates — end walls — have pores to facilitate flow of fluid between cellscompanion cellsnucleated cells connected to the sieve-tube help sieve tubes

Aaaah

…

Structure–Function

again

!

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2006-2007

Plant Growth

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Life Cycle of PlantsAnnuals- in one year Ex:Wildflowers, cropsBiennials- completed in 2 years Ex: radishes and carrotsPerennials- continues for many years Ex. Trees

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Growth in Plants Specific regions of growth: meristemsstem cells: perpetually embryonic tissueregenerate new cellsapical shoot meristemgrowth in length

primary growthapical root meristemgrowth in lengthprimary growthlateral meristemgrowth in girth

secondary growth

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Apical meristemsshoot

root

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Root structure & growth

protecting the meristem

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Shoot growth

Young leaf

primordium

Apical meristem

Older leaf

primordium

Lateral bud

primordium

Vascular tissue

protecting the meristem

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Woody plants grow in height from tipprimary growthapical meristemWoody plants grow in diameter from sidessecondary growthlateral meristems

vascular cambiummakes 2° phloem & 2° xylemcork cambiummakes barkGrowth in woody plants

Primary

phloem

Primary

xylem

Secondary

phloem

Secondary

xylem

Annual

growth

layers

Lateral

meristems

Primary

xylem

Primary

phloem

Bark

Epidermis

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Vascular cambiumlast year’s xylem

early

latephloem

bark

Phloem

produced to the

outside

Xylem

produced to the

inside

cork

cambium

vascular

cambium

xylem

Why are early

& late growth

different?

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Woody stemcork cambium

vascular cambium

xylem

early

late

phloem

bark

How old is

this tree?

1

2

3

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Secondary Growth produced by the vascular cambium

Vascular cambium

Growth

Secondary

xylem

After one year

of growth

After two years

of growth

Secondary

phloem

Vascular

cambium

X

X

X

X

X

X

P

P

P

P

C

C

C

C

C

C

C

C

C

C

C

C

C

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Plant hormones auxingibberellinsabscisic acidethyleneand more…

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Auxin (IAA)Effectscontrols cell division & differentiation

phototropismgrowth towards lightasymmetrical distribution of auxincells on darker side elongate faster than cells on brighter sideapical dominance

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GibberellinsFamily of hormonesover 100 different gibberellins identifiedEffectsstem elongationfruit growthseed germination

plump grapes in grocery stores have been treated with gibberellin hormones while on the vine

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Abscisic acid (ABA)Effectsslows growthseed dormancyhigh concentrations of abscisic acid germination only after ABA is inactivated or leeched outsurvival value: seed will germinate only under optimal conditionslight, temperature, moisture

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EthyleneHormone gas released by plant cellsEffectsfruit ripening leaf drop like in Autumn apoptosis

One bad apple

spoils the

whole bunch

…

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Fruit ripeningAdaptationhard, tart fruit protects developing seed from herbivoresripe, sweet, soft fruit attracts animals to disperse seedMechanismtriggers ripening processbreakdown of cell wallsofteningconversion of starch to sugarsweeteningpositive feedback systemethylene triggers ripening

ripening stimulates more ethylene production

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Apoptosis in plantsWhat is the evolutionary advantage of loss of leaves in autumn?Many events in plants involve apoptosis

response to hormonesethyleneauxindeath of annual plant after floweringsenescencedifferentiation of xylem vesselsloss of cytoplasm

shedding of autumn leaves

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2006-2007

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