2006-2007 AP Biology

Plant AnatomyChapter 35

AP Biology

Basic plant anatomy 1 root

root tip root hairs

AP Biology

Roots Roots anchor plant in soil, absorb

minerals & water, & store food fibrous roots (1)

mat of thin roots that spread out monocots

tap roots (2) 1 large vertical root also produces many small lateral,

or branch roots dicots

root hairs (3) increase absorptive

surface area

2

1

3

AP Biology

Basic plant anatomy 2 root

- fungi at tips of the roots Mycorrhizae

- -Symbiotic relationship

shoot (stem) buds

terminal or apical buds-located at the top

axillary buds-located at the V formed b/t leaf and stem

AP Biology

Modified shootsstolons (strawberries) rhizome (ginger)

tuber (potato) bulb (onion)

AP Biology

Leaves Function of leaves

photosynthesis energy production CHO production

gas exchange transpiration simple vs. compound

AP Biology

AP Biology

Putting it all together Obtaining raw materials

sunlight leaves = solar collectors

CO2

stomates = gas exchange

H2O uptake from roots

nutrients uptake from roots

AP Biology

Plant TISSUES Dermal

epidermis (“skin” of plant) single layer of tightly

packed cells that covers & protects plant

Ground bulk of plant tissue photosynthetic mesophyll,

storage Vascular

transport system in shoots & roots

xylem & phloem

AP Biology

Plant CELL types in plant tissues Parenchyma

“typical” plant cells = least specialized photosynthetic cells, storage cells tissue of leaves, stem, fruit, storage roots

Collenchyma unevenly thickened primary walls support

Sclerenchyma very thick, “woody” secondary walls support rigid cells that can’t elongate dead at functional maturity

If I’d onlyhad triplets!

AP Biology

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

AP Biologytracheids

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 H2O transpirational pull

AP Biology

Phloem: food-conducting cells carry sugars & nutrients throughout plant

sieve tube

companion cell

living cells

plasmodesmata sieve plate

AP Biology

Phloem: food-conducting cells sieve tube elements & companion cells

AP Biology

Phloem Living cells at functional maturity

cell membrane, cytoplasm control of diffusion

lose their nucleus, ribosomes & vacuole more room for specialized transport of

liquid food (sucrose)

Cells sieve tubes

sieve plates — end walls — have pores to facilitate flow of fluid between cells

companion cells nucleated cells connected to the sieve-tube help sieve tubes

Aaaah…Structure–Function

again!

2006-2007 AP Biology

Plant GrowthChapter 35

AP Biology

Life Cycle of Plants Annuals- in one year Ex:Wildflowers,

crops Biennials- completed in 2 years Ex:

radishes and carrots Perennials- continues for many years

Ex. Trees

AP Biology

Growth in Plants Specific regions of growth: meristems

stem cells: perpetually embryonic tissue regenerate new cells

apical shoot meristem growth in length primary growth

apical root meristem growth in length primary growth

lateral meristem growth in girth secondary growth

AP Biology

Apical meristems

shoot root

AP Biology

Root structure & growth

protecting the meristem

AP Biology

Shoot growth

Young leafprimordium

Apical meristem

Older leafprimordium

Lateral budprimordium

Vascular tissue

protecting the meristem

AP Biology

Woody plants grow in height from tip

primary growth apical meristem

Woody plants grow in diameter from sides

secondary growth lateral meristems

vascular cambium makes 2° phloem & 2° xylem

cork cambium makes bark

Growth in woody plants

Primaryphloem Primary

xylemSecondaryphloem

Secondaryxylem

Annualgrowthlayers

Lateralmeristems

Primaryxylem

Primaryphloem

Bark

Epidermis

AP Biology

Vascular cambium

last year’s xylemearly

late

phloem

bark

Phloem produced to the outside Xylem produced to the inside

corkcambium

vascularcambium

xylem

Why are early & late growth

different?

AP Biology

Woody stem cork cambium

vascular cambium

xylem

earlylate

phloem bark

How old is this tree?

12

3

AP Biology

Secondary Growth produced by the vascular cambium

Vascular cambium Growth

Secondaryxylem

After one yearof growth

After two yearsof growth

Secondaryphloem

VascularcambiumX X

X X

X

X

P P

P

P

C

C

C

C

C

C

C C C

C C

CC

AP Biology

Plant hormones Ch:39 auxin gibberellins abscisic acid ethylene and more…

AP Biology

Auxin (IAA) Effects

controls cell division & differentiation

phototropism growth towards light asymmetrical distribution of auxin cells on darker side elongate faster

than cells on brighter side apical dominance

AP Biology

Gibberellins Family of hormones

over 100 different gibberellins identified

Effects stem elongation fruit growth seed germination

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

AP Biology

Abscisic acid (ABA) Effects

slows growth seed dormancy

high concentrations of abscisic acid germination only after ABA is inactivated or

leeched out

survival value: seed will germinate only under optimal conditions

light, temperature, moisture

AP Biology

Ethylene Hormone gas released by plant cells Effects

fruit ripening leaf drop

like in Autumn apoptosis

One bad apple spoils the

whole bunch…

AP Biology

Fruit ripening Adaptation

hard, tart fruit protects developing seed from herbivores

ripe, sweet, soft fruit attracts animals to disperse seed

Mechanism triggers ripening process

breakdown of cell wall softening

conversion of starch to sugar sweetening

positive feedback system ethylene triggers ripening ripening stimulates more ethylene production

AP Biology

Apoptosis in plantsWhat is the evolutionary advantage of loss of leaves in autumn?

Many events in plants involve apoptosis

response to hormones ethylene auxin

death of annual plant after flowering

senescence differentiation of xylem vessels

loss of cytoplasm shedding of autumn leaves

2006-2007 AP Biology

Don’t take this lying down…

Ask Questions!!