AP Biology 2006-2007

Plant Anatomy

AP Biology

Basic plant anatomy 1 root

root tip root hairs

AP Biology

Plant Body Hierarchy Tissue

Cells with a common function Organ

3 basic organs Roots Stems Leaves

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

root tip root hairs

shoot (stem) nodes

internodes buds

terminal or apical buds axillary buds flower buds & flowers

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Modified shootsstolons (strawberries) rhizome (ginger)

tuber (potato) bulb (onion)

AP Biology

Basic plant anatomy 3 root

root tip root hairs

shoot (stem) nodes

internodes buds

terminal or apical buds axillary buds flower buds & flowers

leaves mesophyll tissue veins (vascular bundles)

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Leaves Function of leaves

photosynthesis energy production CHO production

gas exchange transpiration simple vs. compound

AP Biologysucculent leaves

Modified leavestendrils (peas) spines (cacti)

colored leaves (poinsetta)

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AP Biology

Both systems depend on the other roots depend on

sugars produced by photosynthetic leaves

shoots depend on water & minerals absorbed from the soil by roots

Interdependent systems

water &minerals

sugars

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

Parenchyma Parenchyma cells are unspecialized, thin, flexible &

carry out many metabolic functions all other cell types in plants develop from parenchyma

AP Biology

Collenchyma Collenchyma cells have thicker primary walls &

provide support help support without restraining growth remain alive in maturity

the strings in celery stalksare collenchyma

AP Biology

Sclerenchyma Thick, rigid cell wall

lignin (wood) cannot elongate mostly dead at maturity

Cells for support xylem vessels xylem tracheids fibers

rope fibers sclereids

nutshells seed coats grittiness in pears

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

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

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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!

AP Biology

Vascular tissue in stems

dicottrees & shrubs

monocotgrasses & lilies

collect annual rings

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Vascular tissue in roots: dicot

xylemphloem

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xylem

phloem

Vascular tissue in roots: monocot

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Putting it all together Obtaining raw materials

sunlight leaves = solar collectors

CO2

stomates = gas exchange H2O

uptake from roots nutrients

uptake from roots

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Plant Growth Apical meristem

Growth in length Primary

Lateral meristem Growth in diameter Secondary

AP Biology

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

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Primary growth of roots Root cap

Protects root as it grows Cell division (mitosis)

Cells small Cell elongation Cell differentiation

Cells mature into

final cell types

AP Biology

Primary growth of stems Shoot apical

meristem Dividing cells at

shoot tip

Develop from axillary bud on stem’s surface

AP Biology

Secondary plant growth: vascular cambium Adds secondary

xylem & phloem Thickens roots &

stems Heartwood

Close to center Does not transport

water Sapwood

Transport xylem sap

Outer layers

AP Biology

Secondary plant growth: cork cambium Periderm

Cork cambium & tissues

Produces thick covering Protects from water

loss Phelloderm

Thin layer of parenchyma

Secondary tissue Exterior of cork

cambium Suberin - waxy