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Chapter 35.

Plant Anatomy

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Figure 35.0 The effect of submersion in water on leaf development in Cabomba

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Basic anatomy root shoot (stem) leaves

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Shoots Shoots consist of stems,

leaves & buds Stems

nodes = points at which leaves are attached

internodes = stem segments between nodes

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Shoots

Budsgrowth of shoot

terminal or apical bud = at tip of plant

axillary bud = in nodes on stem

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Modified shootsstolons (strawberries) rhizome (ginger)

tuber (potato) bulb (onion)

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Roots Functions

1. anchor plant

2. absorb minerals & water

3. store food

root hairs increase absorptive

surface area

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Roots Types

fibrous roots mat of thin roots that spread out Monocots

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

or branch roots dicots

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Leaves: Functions

simple vs. compound

1. photosynthesisenergy productionCHO production

2. gas exchange

3. transpiration

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Stomates Function of stomates?

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Modified leavestendrils (peas) spines (cacti)

colored leaves (poinsetta)

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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 tissues Dermal

epidermis single layer of tightly

packed cells that covers & protects plant

Vascular xylem & phloem transport materials

between roots & shoots Ground

cortex, pith everything else:

storage, photosynthetic

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Review of Plant Cell Walls

Cell wall of Cellulose

Primary Cell Wall (first)

Secondary Cell wall (more rigid)

Middle Lamella

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Plant cell types in tissues Parenchyma

Only thin primary cell walls

Most abundant Fns: photosynthetic

cells, storage cells tissue of leaves, stem,

fruit, storage roots

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Parenchyma Parenchyma cells are relatively unspecialized, thin,

flexible & carry out many metabolic functions all types of cells develop from parenchyma

Functions: Storage and PS

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Plant cell types in tissues Collenchyma

unevenly thickened primary walls = support

No secondary walls

FN: support

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The strings in celery stalksare collenchyma

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Collenchyma Collenchyma cells have thicker primary walls &

provide support help support without restraining growth remain alive in maturity

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Plant cell types in tissues

Sclerenchyma very thick, lignified secondary walls =

support rigid cells that can’t elongate dead at functional maturity

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Sclerenchyma Thick, rigid cell wall

lignin cannot elongate mostly dead at maturity

Support cells fibers

rope fibers Sclereids = stone cells

nutshells seed coats grittiness in pears

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Vascular tissue Transports materials in roots, stems & leaves

Xylem carry water & minerals up from roots tube-shaped dead cells

only their walls provide a system of microscopic water pipes

Phloem nutrient-conducting cells

distribute sugars, amino acids & other organic products throughout plant

living tissue arranged into tubes

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Xylem

Elongated dead cells tracheids

long, thin cells with tapered ends walls reinforced with lignin = support thinner pits in end walls allows water flow

vessel elements wider, shorter, thinner walled & less tapered perforated ends walls allows free water flow

Dead at functional maturity

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Xylemwater-conducting cells of xylem

tracheids

vesselelements

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

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Phloem Cells

sieve tubes end walls, sieve plates, have pores to

facilitate flow of fluid between cells companion cells

nucleated cells connected to the sieve-tube help sieve tubes

Living cells at functional maturity lack nucleus, ribosomes & a vacuole specialized for liquid food transport

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Phloem sieve plate

sieve tubes

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Vascular tissue in herbaceous stemsdicot monocot

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Root structure: dicot

xylemphloem

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Root structure: monocot

Endodermis is a selective barrier

Pericycle cells may be meristematic

Secondary roots arise here

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Figure 35.16 The formation of lateral roots

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Plant Growth

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Indeterminate growth Unlike animals most plants grow

throughout their life annuals

life cycle within 1 year germination flowering seed production

perennials live many years does not die of old age, only disease or

trauma

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Meristems Regions of growth

perpetual embryonic tissue regenerate new cells

apical shoot meristem growth in length primary growth

apical root meristem growth in length primary growth

lateral meristems growth in girth secondary growth

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Apical meristems

shoot root

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Root structure & growth

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Shoot growth Terminal

(apical) bud & primary growth of shoot region of

stem growth

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Shoot growth Since woody plants grow from year to

year, they evolved a different growth system than herbaceous plants which die back each year

woody herbaceous

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Growth in woody plants Primary growth

restricted to youngest parts of plant tips of roots & shoots (apical meristem)

Secondary growth thickens & strengthens older part of tree cork meristem makes bark

growing ring around tree = cork cambium

vascular meristem makes xylem & phloem growing ring around tree = vascular cambium

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Woody stem cork cambium

vascular cambium

xylem

earlylate

phloem bark

How old is this tree?

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Woody stem

corkcambium

vascularcambium

xylemearly

late

phloem

bark

Phloem produced to the outside Xylem produced to the inside

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Woody plants grow in height from tip apical meristem

Woody plants grow in diameter (girth) from sides vascular

cambium

Growth in woody plants

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Tree trunk anatomy

tree girdling

What does girdling do to a tree?