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Stamen

Petal

Filament

Anther Carpel Stigma

Ovary

Style

Ovule

Sepal

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(b) Side view of flowers with organ identity mutations

(a) A schematic diagram of the ABC hypothesis

Wild type Mutant lacking A

Stamen Carpel

Petal

Sepal Mutant lacking B Mutant lacking C

Stamens Carpels

Petals Sepals

Stamen

Carpel

Petal

Sepal

A B

C

C gene activity B + C

gene activity

A + B gene

activity

A gene activity

Active genes: Whorls:

A B

C B B B

A A A C C C A B B B B A A A

A A C B

C B B B

C C C C C C A C A A A C C C A A

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Discharged sperm nuclei (n)

Carpel Anther

Ovary

Seed

Germinating seed

Seed coat (2n) Endosperm (3n)

Embryo (2n)

Mature flower on sporophyte plant (2n)

Female gametophyte (embryo sac)

Nucleus of developing endosperm (3n)

Zygote (2n) Egg nucleus (n)

Egg (n)

Antipodal cells

Synergids

Polar nuclei in central cell

Haploid (n) Diploid (2n)

Key

MEIOSIS

FERTILIZATION

Sperm (n)

Pollen tube

Integuments

Surviving megaspore (n)

Megasporangium (2n)

Style

Pollen grains

Sperm

Stigma Pollen tube

Tube nucleus

Tube cell Generative cell Ovule with

megasporangium (2n) Male

gametophyte (in pollen grain) (n)

MEIOSIS Microspore (n)

Microsporocytes (2n) Microsporangium

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Abiotic pollination by wind Pollination by insects

Common dandelion under ultraviolet light

Common dandelion under normal light

Hazel staminate flower (stamens only)

Hazel carpellate flower (carpels only)

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Pollination by bats or birds

Long-nosed bat feeding on cactus flower at night

Hummingbird drinking nectar of columbine flower

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Zygote (2n) (egg plus sperm)

Endosperm nucleus (3n) (two polar nuclei plus sperm)

Polar nuclei

Polar nuclei

Pollen grain

Ovule

Egg

Synergid

Two sperm Ovule

Two sperm

Egg

Stigma Pollen tube

Style Ovary

Micropyle

Tube nucleus

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Ovule

Integuments

Zygote

Terminal cell

Suspensor

Seed coat

Proembryo

Endosperm nucleus

Zygote

Basal cell

Basal cell

Endosperm Suspensor

Root apex Shoot apex Cotyledons

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Seed coat

Endosperm

Radicle Hypocotyl

Epicotyl

Cotyledons

Seed coat

Radicle Hypocotyl Epicotyl

Cotyledons

Pericarp fused with seed coat

Radicle Hypocotyl Epicotyl

Scutellum (cotyledon)

Endosperm Coleoptile

Coleorhiza

(c) Maize, a monocot

(a) Common garden bean, a eudicot with thick cotyledons

(b) Castor bean, a eudicot with thin cotyledons

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Radicle

Hypocotyl Epicotyl

Cotyledon

Foliage leaves

Coleoptile

Seed coat

(b) Maize

Cotyledon

Hypocotyl Cotyledon

Hypocotyl

Foliage leaves

Coleoptile

Radicle

(a) Common garden bean

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(b) Aggregate fruit

Stamen

(a) Simple fruit (c) Multiple fruit (d) Accessory fruit

Stamen

Stamen

Ovary

Stigma

Stigma

Stigma

Ovary

Stamen

Ovary (in receptacle)

Ovule Ovule

Seed

Pea flower

Pea fruit

Raspberry flower

Carpels

Pineapple inflorescence

Raspberry fruit

Carpel (fruitlet)

Pineapple fruit Apple fruit

Each segment develops from the carpel of one flower

Flower Style Petal

Sepal

Apple flower

Sepals

Seed

Remains of stamens and styles

Receptacle

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Dispersal by water

Coconut seed embryo, endosperm, and endocarp inside buoyant husk

Giant seed of the tropical Asian climbing gourd Alsomitra macrocarpa

Dispersal by wind

Dandelion “seeds” (actually one-seeded fruits) Dandelion fruit

Tumbleweed Winged fruit of a maple 12

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Dispersal by animals

Fruit of puncture vine (Tribulus terrestris)

Seeds dispersed in black bear feces

Squirrel hoarding seeds or fruits underground

Ant carrying seed with attached “food body”

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(a) Staminate flowers (left) and carpellate flowers (right) of a dioecious species

(b) Thrum and pin flowers Thrum flower Pin flower

Stamens Stamens Styles

Styles

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Asexual reproduction in aspen trees 15 © 2014 Pearson Education, Inc.

Developing root Laboratory cloning of a garlic plant

(c) (a) (b)

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