Biology Sylvia S. Mader Michael Windelspecht Chapter 27 Flowering Plants: Reproduction Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission

BiologySylvia S. Mader

Michael Windelspecht

Chapter 27 Flowering Plants:

ReproductionLecture Outline

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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27.1 Sexual Reproductive Strategies

• Plants have a two-stage, alternating life cycle– Sporophyte produces haploid spores by meiosis– Spores divide mitotically to become haploid

gametophytes– Gametophytes produce gametes– Gametes fuse to produce a diploid zygote– Zygote divides mitotically to become the diploid

sporophyte

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Sexual Reproduction in Flowering Plants

3

mitosis

mitosis

1

6

7

8

FERTILIZATION

seed

sporophyte

egg

sperm

Male gametophyte(pollen graIn)

haploid(n)

diploid(2n)

3

4

MEIOSIS

Female gametophyte(embryo sac)

megaspore

2

ovaryovule

anther

microspore

5

zygote


Sexual Reproductive Strategies

• A flower produces two types of spores– Microspore - Male gametophyte

• Undergoes mitosis• Becomes pollen grain

– Megaspore - Female gametophyte• Undergoes mitosis• Becomes the female gametophyte, an embryo

sac within an ovule within an ovary• Ovule becomes a seed• Ovary becomes a fruit

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• Flowers– Flowering occurs in response to

environmental signals such as day length• In monocots, flower parts occur in threes and

multiples of three• In eudicots, flower parts occur in fours or fives and

multiples of four or five

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• A typical flower has four whorls of modified leaves attached to a receptacle at the end of a flower stalk called a peduncle– Sepals protect the bud– Petals attract pollinators– Stamens are male portion of flower

• Anther - Saclike container• Filament - Slender stalk

– Carpel is the female portion of flower• Stigma - Enlarged sticky knob• Style - Slender stalk• Ovary - Enlarged base enclosing ovules

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Anatomy of a Flower

7


stamenanther

filament

carpelstigma

styleovaryovulepetal

sepal receptacle

peduncle

Monocot vs. Eudicot Flowers

8


b. Festive azalea, Rhododendron sp.

carpel

stamen

petal p1

p2

p3

p4

p5

b: © Pat Pendarvis


• Complete vs. incomplete flowers:– Complete flowers have sepals, petals, stamens, and a

carpel– Incomplete flowers are missing one or more of above

• Perfect vs. imperfect flowers:– Perfect (bisexual) flowers have both stamens and carpels– Imperfect (unisexual) flowers have one but not the other

• Monoecious vs. dioecious plants– Monoecious plants have staminate flowers and carpellate

flowers on the same plant– Dioecious plants have staminate and carpellate flowers on

separate plants

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Monoecious and Dioecious Plants

10


b.a.(a): © Radius Images/Getty RF; (b): © Garden World Images/age fotostock

Life Cycle of Flowering Plants

11

generative cell

tube cellMicrospores

Megaspores

Pollination

polar nuclei

egg

Seed

Mature Seed

Sporophyteendosperm (3n)

embryo

seed coat

Pollen sac

anther

Ovule

egg cell

antipodals

synergids

polar nuclei

ovary

mitosis

mitosis

sperm

MEIOSIS

mitosis

MEIOSIS

megaspore

integument

micropyle

anther

ovuleovary

ovulewall

sperm

diploid (2n)

haploid (n)

The ovuledevelops into aseed containingthe embryonic sporophyte and endosperm.

DOUBLE FERTILIZATION

Development of the malegametophyte:

In pollen sacs of the anther , amicrospore mother cell undergoesmeiosis to produce 4 microsporeseach

Development of the femalegametophyte:

In an ovule within an ovary, amegaspore mother cellundergoes meiosis to Produce 4 megaspores.

megasporemother cell

microsporemother cell

ovulewall

3 megasporesdisintegrate

Embryo sac(mature female gametophyte)

Microsporesdevelop into malegametophytes(pollen grains).

One megasporebecomes theembryo sac(femalegametophyte).

Pollen grain(male gametophyte)

Development ofthe sporophyte:

Pollinationoccurs;a pollen graingerminates andproduces a pollen

pollentube

tubecellnucleus

Mature malegametophyte

During doublefertilization, onesperm from theMale gametophyteWill fertilize theegg; anotherSperm will join withpolar nuclei toproduce the 3nendosperm.


(Top): Courtesy Graham Kent; (Bottom): © Ed Reschke


• Male Gametophytes– Microspores are produced in anthers– Each anther has four pollen sacs, each with

many microspore mother cells• Microspore mother cells undergo meiosis to

produce microspores• Microspores undergo mitosis to produce pollen

grains

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• The ovary contains one or more ovules– An ovule has a central mass of parenchyma cells

covered by integuments– One parenchyma cell enlarges to become a

megaspore mother cell• The megaspore mother cell undergoes meiosis to produce

four haploid megaspores, three of which are nonfunctional• The functional megaspore divides mitotically until there are

eight nuclei in the female gametophyte– The female gametophyte (embryo sac) contains

• One egg cell associated with two synergid cells• One central cell with two polar nuclei• Three antipodal cells

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• Pollination – The transfer of pollen from an anther to the

stigma of a carpel• Self-pollination occurs if the pollen is from

the same plant• Cross-pollination occurs if the pollen is from

a different plant

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Pollination

15


a.

b.

c. 8 m

118 m

a: © George Bernard/Animals Animals/Earth Scenes; b: © Simko/Visuals Unlimited; c: © Dwight Kuhn


• Fertilization• When a pollen grain lands on the stigma, it

germinates, forming a pollen tube• The pollen tube passes between the stigma and style

to reach the micropyle of the ovule• Double fertilization occurs

– One sperm nucleus unites with the egg nucleus, producing a 2n zygote

– The other sperm nucleus unites with the polar nuclei, forming a 3n endosperm nucleus, which develops into the endosperm

• A mature seed contains the embryo, stored food, and the seed coat

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Plants and Their Pollinators

17


a. b.Aa: © Steven P. Lynch; Ab: © Robert Maier/Animals/Animals/Earth Scenes

Plants and Their Pollinators

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a. b.Ba: © Anthony Mercieca/Photo Researchers, Inc.; Bb: © Merlin D. Tuttle/Bat Conservation International;

27.2 Seed Development

• Development: – Programmed series of stages from a simple to

a more complex form– Development of a eudicot embryo

• After double fertilization, the zygote divides repeatedly to form a proembryo and a suspensor

– During the globular stage, the proembryo is a ball of cells

• The outermost cells will become dermal tissue

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Seed Development

• Heart and Torpedo Stages• The embryo is heart shaped when

cotyledons appear• The embryo enlarges, elongates, and takes

on a torpedo shape

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Seed Development

• Mature Embryo– The epicotyl is the portion between cotyledons

contributing to shoot development– The hypocotyl is the portion below that contributes

to stem development– The radicle is the embryonic root

21

Development of an Eudicot Embryo

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1 2

endosperm nucleus

zygote

zygote

basal cell

endosperm

Arabidopsis thaliana

embryo

suspensor

Zygote stage: Doublefertilization results in zygote(true green) and endosperm.

Proembryo stage: Embryo(green) is multicellular andthe suspensor (purple) isfunctional.

(Proembryo): Courtesy Dr. Chun-Ming Liu; (Torpedo): © Biology Media/Photo Researchers, Inc.; (Mature embryo): © Jack Bostrack/Visuals Unlimited


Development of an Eudicot Embryo (continued)

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A. thaliana

endosperm cotyledons appearing

A. thaliana

endosperm

CapsellaCapsella

cotyledons

3 4 5 6

hypocotyl(root axis)

epicotyl (shootapical meristem)

seedcoat

radicle(root apicalmeristem)

Mature embryo stage: Theepicotyl will be the shootsystem; the hypocotyl willbe the root system.

rootapicalmeristem

bendingcotyledons

shoot apicalmeristem

Torpedo stage: Embryo istorpedo shaped; thecotyledons are obvious.

Heart stage: Embryo isheart shaped.

Globular stage:Embryo is globeshaped.

(Proembryo): Courtesy Dr. Chun-Ming Liu; (Torpedo): © Biology Media/Photo Researchers, Inc.; (Mature embryo): © Jack Bostrack/Visuals Unlimited

Monocot vs. Eudicot

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embryoembryo

endosperm

pericarp

cotyledon

coleorhiza

coleoptile

plumule

radicle

cotyledon

hypocotyl

seed coat

plumule

radicle

a. b.

a: © Dwight Kuhn; b: Courtesy Ray F. Evert/University of Wisconsin Madison

27.3 Fruit Types and Seed Dispersal

• A fruit is a mature ovary• Simple Fruits

– Simple fruits are derived from single ovary with one or several chambers

• Compound fruits develop from several groups of ovaries– Aggregate Fruits

• Ovaries are from a single flower one receptacle• Blackberry

– Multiple Fruits • Ovaries are from separate flowers clustered together• Pineapple

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26

Fruit Types and Seed Dispersal

• Fruit Development– The ovary wall thickens to become the

pericarp, which can have three layers• The exocarp forms the outermost skin• The mesocarp is the fleshy tissue between the

exocarp and the endocarp• The endocarp is the boundary around the seeds


• Fruit Types– In dry fruits, the pericarp is paper, leathery, or

woody when the fruit is mature• Dehiscent - the fruit splits open when ripe

– Legumes• Indehiscent - the fruit does not split open when ripe

– Grains

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Fruits

28

Legume

Drupe

seed coveredby pericarp

pericarpseed

wing

one fruit

exocarp

pericarp

exocarp (skin)

mesocarp (flesh)

Samara

Aggregate Fruit Multiple Fruit

endocarp (pitcontains seed)

chamber ofovary has

many seeds

fruits from ovariesof many flowers

True Berry

a. A drupe is a fleshy fruit with a pit containing a single seed produced from a simple ovary.

b. A berry is a fleshy fruit having seeds and pulp produced from a compound ovary.

e. An aggregate fruit contains many fleshy fruits produced from simple ovaries of the same flower.

f. A multiple fruit contains many fused fruits produced from simple ovaries of individual flowers.


a, b: © Kingsley Stern; c: © Dr. James Richardson/Visuals Unlimited; d: © James Mauseth; e: Courtesy Robert A. Schlising; f: © Ingram Publishing/Alamy

c. A legume is a dry dehiscent fruit produced from a simple ovary. d. A samara is a dry indehiscent fruit produced from a simple ovary .

fruit from manyovaries of asingle flower


• Dispersal of Fruits

– Many dry fruits are dispersed by wind

• Woolly hairs, plumes, wings

– Many fruits attract animals and provide them with food

• Peaches, cherries, tomatoes

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Fruit Dispersal by Animals

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a. b.a: © Marie Read/Animals Animals/Earth Scenes; b: © Scott Camazine/Photo Researchers, Inc.


• Seed Germination– When seed germination occurs, the embryo

resumes growth and metabolic activity– Length of time seeds retain their viability is

quite variable– Some seeds do not germinate until they have

been through a dormant period• Temperate zones - Cold Weather

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• Environmental requirements for seed germination– Availability of oxygen for metabolic needs– Adequate temperature for enzyme activity– Adequate moisture for hydration of cells

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Eudicot and Monocot Seed Structure and Germination

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Corn kernel

endosperm

pericarp

coleorhiza

coleoptile

plumule

radicle

coleoptile

radicle

coleoptile

first leaf

primary root

prop root

true leaf

coleorhiza

Corn germination and growth

cotyledon

hypocotyl

seed coat

plumule

radicle

Seed structure

Bean germination and growtha. b.

hypocotyl

epicotyl

hypocotyl

cotyledons(two)

cotyledon(one)

witheredcotyledons

secondaryroot

primaryroot

adventitiousroot

seedcoat

primaryroot

cotyledons(two)

first true leaves(primary leaves)

a: © Ed Reschke; b: © James Mauseth

27.4 Asexual Reproduction in Plants

• Plants can reproduce asexually with the use of – Stolons – horizontal stems– Rhizomes – underground stems

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Asexual Reproduction in Plants

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Parent plant

Asexually produced offspringstolon

© G.I. Bernard/Animals Animals/Earth Scenes

Asexual Reproduction in Plants

• Tissue culture is the growth of a tissue in an artificial liquid or solid culture medium– Many plant cells are totipotent

• Each has the genetic capability of becoming an entire plant

• Somatic embryogenesis– Hormones stimulate development of plantlets from

leaf or other tissue

• Somaclonal variations– Mutations leading to new plants with desirable

traits

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37

Asexual Reproduction in Plants• Meristem tissue

– Results in clonal plants with identical traits

• Anther tissue culture– Haploid cells in pollen grains are cultured to produce

haploid plantlets– A diploid plantlet can be produced by adding a

chemical agent that encourages chromosome doubling• Cell Suspension Culture

– Rapidly growing calluses are cut into small pieces and shaken into a liquid nutrient medium

• Single cells or small clumps break off and form a suspension

Asexual Reproduction Through Tissue Culture

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a. Protoplasts, naked cells b. Cell wall regeneration

c. Aggregates of cells d. Callus, undifferentiated mass

e. Somatic embryo f. Plantlet(All): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604


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Biology Sylvia S. Mader Michael Windelspecht Chapter 27 Flowering Plants: Reproduction Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission