CAMPBELL - Weebly · 2019. 5. 2. · CAMPBELL BIOLOGY Reece • Urry • Cain • Wasserman •...

CAMPBELL

BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson

© 2014 Pearson Education, Inc.

TENTH

EDITION

38 Angiosperm Reproduction

and Biotechnology

Lecture Presentation by

Nicole Tunbridge and

Kathleen Fitzpatrick


Flowers of Deceit

Insects help angiosperms to reproduce sexually

with physically distant members of their own

species

For example, male long-horned bees mistake

Ophrys flowers for females and attempt to mate

with them

The flower is pollinated in the process

Unusually, the flower does not produce nectar and

the male receives no benefit


Figure 38.1


Figure 38.1a


Many angiosperms lure insects with nectar; both

plant and pollinator benefit

Mutualistic symbioses are common between

plants and other species

Angiosperms can reproduce sexually and

asexually

Angiosperms are the most important group of

plants in terrestrial ecosystems and in agriculture


Concept 38.1: Flowers, double fertilization, and fruits are key features of the angiosperm life cycle

Plant life cycles are characterized by the

alternation between sporophyte (spore-producing)

and gametophyte (gamete-producing) generations


In angiosperms, the sporophyte is the plant that

we see; they are larger, more conspicuous and

longer-lived than gametophytes

The angiosperm life cycle is characterized by

“three Fs”: f lowers, double fertilization, and f ruits


Flower Structure and Function

Flowers are the reproductive shoots of the

angiosperm sporophyte; they attach to a part of

the stem called the receptacle

Flowers consist of four floral organs: carpels,

stamens, petals, and sepals

Stamens and carpels are reproductive organs;

sepals and petals are sterile


Figure 38.2

Anther

Filament

Stamen

Petal

Sepal

Ovary

Carpel Stigma

Style

Ovule

Receptacle


Video: Flower Blooming (Time Lapse)


A carpel has a long style with a stigma on which

pollen may land

At the base of the style is an ovary containing one

or more ovules

A single carpel or group of fused carpels is called

a pistil

A stamen consists of a filament topped by an

anther with pollen sacs that produce pollen


Complete flowers contain all four floral organs

Incomplete flowers lack one or more floral

organs, for example stamens or carpels

Clusters of flowers are called inflorescences


Much of floral diversity represents adaptation to

specific pollinators

Four general trends can be seen in the evolution

of flowers

Bilateral symmetry

Reduction in the number of floral parts

Fusion of floral parts

Location of ovaries inside receptacles


Figure 38.3a

Bilateral symmetry

Musk mallow

(radial symmetry)

“Bramley” orchid

(bilateral symmetry)


Figure 38.3aa

Musk mallow

(radial symmetry)


Figure 38.3ab

“Bramley” orchid

(bilateral symmetry)


Figure 38.3b

Reduction in number of floral parts

Bloodroot

Drooping trillium


Figure 38.3ba

Bloodroot


Figure 38.3bb

Drooping trillium


Figure 38.3c

Fusion of floral parts

Star of Bethlehem

Hedge bindweed


Figure 38.3ca

Star of Bethlehem


Figure 38.3cb

Hedge bindweed


Figure 38.3d

Ovaries located inside receptacles

Ovary

Ovary

Stone plant (longitudinal section)

Japanese quince (longitudinal section)


Figure 38.3da

Ovary

Stone plant (longitudinal section)


Figure 38.3db

Ovary

Japanese quince (longitudinal section)


The Angiosperm Life Cycle: An Overview

The angiosperm life cycle includes

Gametophyte development

Pollination

Double fertilization

Seed development


Figure 38.4-1

Carpel Anther

Mature flower on

sporophyte plant

(2n)

Microsporangium (pollen sac)

Microsporocytes (2n)

Microspore (n)

Male

gametophyte

(in pollen

grain) (n)

MEIOSIS

Generative cell

Tube cell

Tube nucleus

Pollen

grains

Key

Haploid (n)

Diploid (2n)


Figure 38.4-2

Carpel Anther

Mature flower on

sporophyte plant

(2n)



Microspore (n)

Male

gametophyte

(in pollen

grain) (n)

MEIOSIS

Generative cell

Tube cell

Tube nucleus

Pollen

grains

Key

Haploid (n)

Diploid (2n)

MEIOSIS

Ovary Ovule with

megasporangium

(2n)

Female

gametophyte

(embryo sac)

Antipodal cells

Polar nuclei

in central cell

Synergids

Egg (n)

Megasporangium

(2n)

Surviving

megaspore (n)

Integuments

Micropyle


Figure 38.4-3

Carpel Anther

Mature flower on

sporophyte plant

(2n)



Microspore (n)

Male

gametophyte

(in pollen

grain) (n)

MEIOSIS

Generative cell

Tube cell

Tube nucleus

Pollen

grains

Key

Haploid (n)

Diploid (2n)

MEIOSIS

Ovary Ovule with

megasporangium

(2n)

Female

gametophyte

(embryo sac)

Antipodal cells

Polar nuclei

in central cell

Synergids

Egg (n)

Megasporangium

(2n)

Surviving

megaspore (n)

Micropyle

Style

Discharged sperm nuclei (n)

Egg

nucleus (n)

FERTILIZATION

Stigma Pollen tube

Sperm

Tube nucleus

Integuments


Figure 38.4-4

Carpel Anther

Mature flower on

sporophyte plant

(2n)



Microspore (n)

Male

gametophyte

(in pollen

grain) (n)

MEIOSIS

Generative cell

Tube cell

Tube nucleus

Pollen

grains

Key

Haploid (n)

Diploid (2n)

MEIOSIS

Ovary Ovule with

megasporangium

(2n)

Female

gametophyte

(embryo sac)

Antipodal cells

Polar nuclei

in central cell

Synergids

Egg (n)

Megasporangium

(2n)

Surviving

megaspore (n)

Micropyle

Style

Discharged sperm nuclei (n)

Egg

nucleus (n)

FERTILIZATION

Germinating

seed

Embryo (2n)

Endosperm (3n)

Seed coat (2n)

Seed

Zygote (2n) Nucleus of

developing

endosperm

(3n)

Stigma Pollen tube

Sperm

Tube nucleus

Integuments


Figure 38.4a

Carpel Anther Microsporangium (pollen sac)


Microspore (n)

Male

gametophyte

(in pollen

grain) (n)

MEIOSIS

Generative cell

Tube cell

Tube nucleus

Key

Haploid (n)

Diploid (2n)


Figure 38.4b

Key

Haploid (n)

Diploid (2n)

MEIOSIS

Ovary Ovule with

megasporangium

(2n)

Megasporangium

(2n)

Surviving

megaspore (n)

Integuments

Micropyle


Figure 38.4c

Key

Haploid (n)

Diploid (2n)

Megasporangium

(2n)

Surviving

megaspore (n)

Integuments

Micropyle

Style

Female

gametophyte

(embryo sac)

Antipodal cells

Polar nuclei

in central cell

Synergids

Egg (n)

Pollen

grains

Stigma Pollen tube

Sperm

Tube nucleus


Figure 38.4d

Female

gametophyte

(embryo sac)

Antipodal cells

Polar nuclei

in central cell

Synergids

Egg (n)

Embryo (2n)

Endosperm (3n)

Seed coat (2n)

Seed

Style

Discharged sperm

nuclei (n)

Egg

nucleus (n)

Zygote (2n) Nucleus of

developing

endosperm

(3n)

Key

Haploid (n)

Diploid (2n)

FERTILIZATION


Video: Flowering Plant Life Cycle (Time Lapse)


Animation: Plant Fertilization


Gametophyte Development

Angiosperm gametophytes are microscopic and

their development is obscured by protective

tissues


Development of Female Gametophytes

(Embryo Sacs)

The embryo sac, or female gametophyte,

develops within the ovule

Within an ovule, two integuments surround a

megasporangium

One cell in the megasporangium undergoes

meiosis, producing four megaspores, only one of

which survives


The megaspore divides without cytokinesis,

producing one large cell with eight nuclei

This cell is partitioned into a multicellular female

gametophyte, the embryo sac


Development of Male Gametophytes in

Pollen Grains

Pollen develops from microspores within

the microsporangia, or pollen sacs, of anthers

Each microspore undergoes mitosis to produce

two cells: the generative cell and the tube cell

A pollen grain consists of the two-celled male

gametophyte and the spore wall


Pollination

In angiosperms, pollination is the transfer of

pollen from an anther to a stigma

After landing on a receptive stigma, a pollen grain

produces a pollen tube that grows down into the

ovary and discharges two sperm cells near the

embryo sac


Double Fertilization

Fertilization, the fusion of gametes, occurs after

the two sperm reach the female gametophyte

One sperm fertilizes the egg, and the other

combines with the two polar nuclei, giving rise to

the triploid food-storing endosperm (3n)

This double fertilization ensures that endosperm

only develops in ovules containing fertilized eggs


Seed Development

After double fertilization, each ovule develops into

a seed

The ovary develops into a fruit enclosing the seed

When a seed germinates, the embryo develops

into a new sporophyte


Methods of Pollination

The transfer of pollen from anthers to stigma can

be accomplished by wind, water, or animals

Wind-pollinated species (e.g., grasses and many

trees) release large amounts of pollen


Figure 38.5a

Abiotic pollination by wind Pollination by bees

Common dandelion

under ultraviolet

light

Common dandelion

under normal light

Hazel staminate flowers

(stamens only) releasing

clouds of pollen

Hazel carpellate

flower (carpels

only)


Figure 38.5aa

Hazel carpellate

flower (carpels

only)


Figure 38.5ab

Hazel staminate flowers

(stamens only) releasing

clouds of pollen


Figure 38.5ac

Common dandelion

under normal light


Figure 38.5ad

Common dandelion

under ultraviolet

light


Figure 38.5b

Pollination by moths

and butterflies

Pollination

by bats Pollination

by flies

Blowfly on carrion

flower

Long-nosed bat feeding

on cactus flower at night Moth on yucca flower

Pollination by birds

Hummingbird drinking nectar of columbine flower

Stigma

Moth

Anther


Figure 38.5ba

Moth on yucca flower

Stigma

Moth

Anther


Figure 38.5bb

Long-nosed bat feeding

on cactus flower at night


Figure 38.5bc

Blowfly on carrion

flower


Figure 38.5bd

Hummingbird drinking nectar of columbine flower


Video: Bat Pollinating Agave Plant


Video: Bee Pollinating


Coevolution is the joint evolution of interacting species in response to selection imposed by each other

Many flowering plants have coevolved with specific pollinators

The shapes and sizes of flowers often correspond to the pollen transporting parts of their animal pollinators

For example, Darwin correctly predicted a moth

with a 28-cm-long tongue based on the morphology

of a particular flower


Figure 38.6


From Seed to Flowering Plant: A Closer Look

The development of a seed into a flowering plant

includes several stages

Endosperm development

Embryo development

Seed dormancy

Seed germination

Seedling development

Flowering


Endosperm Development

Endosperm development usually precedes

embryo development

In most monocots and many eudicots, endosperm

stores nutrients that can be used by the seedling

In other eudicots, the food reserves of the

endosperm are exported to the cotyledons


Embryo Development

The first mitotic division of the zygote splits the

fertilized egg into a basal cell and a terminal cell

The basal cell produces a multicellular suspensor,

which anchors the embryo to the parent plant

The terminal cell gives rise to most of the embryo

The cotyledons form and the embryo elongates


Figure 38.7

Ovule

Endosperm nucleus

Zygote

Integuments

Zygote

Terminal cell

Basal cell

Proembryo

Seed coat

Endosperm

Suspensor

Basal cell

Cotyledons

Shoot apex

Root apex

Suspensor


Animation: Seed Development


Structure of the Mature Seed

The embryo and its food supply are enclosed by a

hard, protective seed coat

The seed enters a state of dormancy

A mature seed is only about 5–15% water


In some eudicots, such as the common garden

bean, the embryo consists of the embryonic axis

attached to two fleshy cotyledons (seed leaves)

Below the cotyledons the embryonic axis is called

the hypocotyl and terminates in the radicle

(embryonic root); above the cotyledons it is called

the epicotyl

The plumule comprises the epicotyl, young leaves,

and shoot apical meristem


Figure 38.8

Seed coat Epicotyl

Hypocotyl

Cotyledons

Radicle

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

(b) Castor bean, a eudicot with thin cotyledons

(c) Maize, a monocot

Seed coat

Cotyledons

Epicotyl

Hypocotyl

Radicle

Endosperm

Scutellum

(cotyledon)

Coleoptile

Coleorhiza

Pericarp fused

with seed coat

Endosperm

Epicotyl

Hypocotyl

Radicle


Figure 38.8a

Seed coat Epicotyl

Hypocotyl

Cotyledons

Radicle

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


Figure 38.8b

(b) Castor bean, a eudicot with thin cotyledons

Seed coat

Cotyledons

Epicotyl

Hypocotyl

Radicle

Endosperm


Figure 38.8c

(c) Maize, a monocot

Scutellum

(cotyledon)

Coleoptile

Coleorhiza

Pericarp fused

with seed coat

Endosperm

Epicotyl

Hypocotyl

Radicle


The seeds of some eudicots, such as castor

beans, have thin cotyledons


A monocot embryo has one cotyledon

Grasses, such as maize and wheat, have a

special cotyledon called a scutellum

Two sheathes enclose the embryo of a grass

seed: a coleoptile covering the young shoot and a

coleorhiza covering the young root


Seed Dormancy: An Adaptation for Tough Times

Seed dormancy increases the chances that

germination will occur at a time and place most

advantageous to the seedling

The breaking of seed dormancy often requires

environmental cues, such as temperature or

lighting changes

Most seeds remain viable after a year or two of

dormancy, but some last only days and others can

remain viable for centuries


Seed Germination and Seedling Development

Germination depends on imbibition, the uptake of

water due to low water potential of the dry seed

The radicle (embryonic root) emerges first; the

developing root system anchors the plant

Next, the shoot tip breaks through the soil surface


In many eudicots, a hook forms in the hypocotyl,

and growth pushes the hook above ground

Light causes the hook to straighten and pull the

cotyledons and shoot tip up


Figure 38.9

Hypocotyl

Radicle

Seed coat

(a) Common garden bean

Coleoptile

Radicle (b) Maize

Foliage leaves

Coleoptile

Hypocotyl

Cotyledon

Cotyledon

Cotyledon

Hypocotyl

Epicotyl

Foliage leaves


Figure 38.9a

Hypocotyl

Radicle

Seed coat

(a) Common garden bean

Hypocotyl

Cotyledon

Cotyledon

Cotyledon

Hypocotyl

Epicotyl

Foliage leaves


Figure 38.9b

Coleoptile

Radicle (b) Maize

Foliage leaves

Coleoptile


In maize and other grasses, which are monocots,

the coleoptile pushes up through the soil creating

a tunnel for the shoot tip to grow through


Flowering

The flowers of a given plant species are

synchronized to appear at a specific time of the

year to promote outbreeding

Flowering is triggered by a combination of

environmental cues and internal signals


Fruit Structure and Function

A fruit is the mature ovary of a flower

It protects the enclosed seeds and aids in seed

dispersal by wind or animals

In some fruits, such as soybean pods, the ovary

wall dries out at maturity, whereas in other fruits,

such as grapes, it remains fleshy


Figure 38.10


Fruits are classified based on their developmental

origin

Simple fruits develop from a single or several

fused carpels

Aggregate fruits result from a single flower with

multiple separate carpels

Multiple fruits develop from a group of flowers

called an inflorescence


Figure 38.11

Stamen

Stamen

Ovary

Ovary

Stigma

Ovule Pea flower

Seed

Pea fruit

(a) Simple fruit

Stigma

Carpels

Raspberry flower

Carpel

(fruitlet)

Stamen

Raspberry fruit

(b) Aggregate fruit

Flowers

(c) Multiple fruit

Pineapple

inflorescence

Each segment develops from the carpel of one flower

Pineapple fruit

(d) Accessory fruit

Apple fruit

Stigma

Stamen

Style Petal

Sepal

Ovule Ovary

(in receptacle)

Apple flower

Remains of

stamens and styles Sepals

Seed Receptacle


Figure 38.11a

Stamen

Stamen

Ovary

Ovary

Stigma

Ovule Pea flower

Seed

Pea fruit

(a) Simple fruit

Stigma

Carpels

Raspberry flower

Carpel

(fruitlet)

Stamen

Raspberry fruit

(b) Aggregate fruit


Figure 38.11b

Flowers

(c) Multiple fruit

Pineapple

inflorescence

Each segment develops from the carpel of one flower

Pineapple fruit

(d) Accessory fruit

Apple fruit

Stigma

Stamen

Style Petal

Sepal

Ovule Ovary

(in receptacle)

Apple flower

Remains of

stamens and styles Sepals

Seed Receptacle


Animation: Fruit Development


An accessory fruit contains other floral parts in

addition to ovaries


Fruit dispersal mechanisms include

Water

Wind

Animals


Figure 38.12a

Dispersal by water

Dispersal by wind

Coconut seed

embryo, endosperm,

and endocarp inside

buoyant husk

Dandelion “seeds” (actually one-seeded fruits)

Giant seed of

the tropical Asian

climbing gourd

Alsomitra macrocarpa

Tumbleweed Winged fruit of a maple

Dandelion fruit


Figure 38.12aa

Coconut seed embryo, endosperm, and endocarp inside buoyant husk


Figure 38.12ab

Giant seed of

the tropical Asian

climbing gourd

Alsomitra macrocarpa


Figure 38.12ac

Dandelion “seeds” (actually one-seeded fruits)

Dandelion fruit


Figure 38.12ad

Winged fruit of a maple


Figure 38.12ae

Tumbleweed


Figure 38.12b

Dispersal by animals

Fruit of puncture vine

(Tribulus terrestris)

Squirrel hoarding seeds or fruits

underground

Ant carrying seed with

attached “food body”

Seeds dispersed in black bear feces


Figure 38.12ba

Fruit of puncture vine

(Tribulus terrestris)


Figure 38.12bb

Squirrel hoarding seeds or fruits

underground


Figure 38.12bc

Seeds dispersed in black bear feces


Figure 38.12bd

Ant carrying seed with

attached “food body”


Concept 38.2: Flowering plants reproduce sexually, asexually, or both

Many angiosperm species reproduce both

asexually and sexually

Sexual reproduction results in offspring that are

genetically different from their parents

Asexual reproduction results in a clone of

genetically identical organisms


Mechanisms of Asexual Reproduction

Fragmentation, separation of a parent plant into

parts that develop into whole plants, is a very

common type of asexual reproduction

In some species, a parent plant’s root system

gives rise to adventitious shoots that become

separate shoot systems


Figure 38.13


Apomixis is the asexual production of seeds from

a diploid cell


Advantages and Disadvantages of Asexual and Sexual Reproduction

Asexual reproduction is also called vegetative

reproduction because progeny arise from mature

vegetative fragments

All genetic material is passed to the progeny

Asexual reproduction can be beneficial to a

successful plant in a stable environment

However, a clone of plants is vulnerable to local

extinction if there is an environmental change


Sexual reproduction generates genetic variation

that makes evolutionary adaptation possible

However, only a fraction of seedlings survive

Some flowers can self-fertilize to ensure that every

ovule will develop into a seed

However, many species have evolved

mechanisms to prevent selfing


Mechanisms That Prevent Self-Fertilization

Many angiosperms have mechanisms that make it

difficult or impossible for a flower to self-fertilize

Dioecious species have staminate and carpellate

flowers on separate plants


Figure 38.14

(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


Figure 38.14a

Staminate flower


Figure 38.14b

Carpellate flower


Figure 38.14c

Thrum flower Pin flower

Stamens

Stamens

Styles

Styles


Others have stamens and carpels that mature at

different times or are arranged to prevent selfing


The most common is self-incompatibility, a

plant’s ability to reject its own pollen

Researchers are unraveling the molecular

mechanisms involved in self-incompatibility

Some plants reject pollen that has an S-gene

matching an allele in the stigma cells

Recognition of self pollen triggers a signal

transduction pathway leading to a block in growth

of a pollen tube


Totipotency, Vegetative Reproduction, and Tissue Culture

Totipotent cells, those that can divide and

asexually generate a clone of the original

organism, are common in plants

Humans have devised methods for asexual

propagation of angiosperms

Most methods are based on the ability of plants to

form adventitious roots or shoots


Vegetative Propagation and Grafting

Vegetative reproduction that is facilitated or

induced by humans is called vegetative

propagation

Many kinds of plants are asexually reproduced

from plant fragments called cuttings

A callus is a mass of dividing, undifferentiated

totipotent cells that forms where a stem is cut and

produces adventitious roots


A twig or bud can be grafted onto a plant of a

closely related species or variety

The stock provides the root system

The scion is grafted onto the stock


Test-Tube Cloning and Related Techniques

Plant biologists have adopted in vitro methods to

create and clone novel plant varieties

A callus of undifferentiated totipotent cells can

sprout shoots and roots in response to plant

hormones


Figure 38.15

(a) (b) (c) Developing root


Some pathogenic viruses can be eliminated by

excising virus-free apical meristems for tissue

culture

Plant tissue culture also facilitates the production

of genetically modified (GM) plants


Concept 38.3: People modify crops by breeding and genetic engineering

People have intervened in the reproduction and

genetic makeup of plants for thousands of years

Hybridization is common in nature and has been

used by breeders to introduce new genes

Maize, a product of artificial selection, is a staple

in many developing countries


Figure 38.16


Figure 38.16a


Figure 38.16b


Plant Breeding

Mutations can arise spontaneously or can be

induced by breeders

Plants with beneficial mutations are used in

breeding experiments

Desirable traits can be introduced from different

species or genera


Plant Biotechnology and Genetic Engineering

Plant biotechnology has two meanings

In a general sense, it refers to innovations in the

use of plants to make useful products

In a specific sense, it refers to use of GM organisms

in agriculture and industry

Transgenic organisms are those that have been

engineered to express a gene from another

species


Reducing World Hunger and Malnutrition

Genetically modified plants may increase the

quality and quantity of food worldwide

Some transgenic crops have been developed to

produce the Bt toxin, which is toxic to insect pests

Other crops are able to tolerate herbicides or

resist specific diseases


Figure 38.17

Non-Bt maize Bt maize


Nutritional quality of plants is being improved

For example, “Golden Rice” is a transgenic variety

being developed to address vitamin A deficiencies

among the world’s poor

For example, transgenic cassava have increased

levels of iron and beta-carotene and reduced

cyanide-producing chemicals


Figure 38.18


Reducing Fossil Fuel Dependency

Biofuels are fuels derived from living biomass,

the total mass of organic matter in a group of

organisms

Biofuels can be produced by rapidly growing crops

such as switchgrass and poplar

Biofuels would reduce the net emission of CO2, a

greenhouse gas


The Debate over Plant Biotechnology

Some biologists are concerned about risks of

releasing GM organisms (GMOs) into the

environment


Issues of Human Health

One concern is that genetic engineering may

transfer allergens from a gene source to a plant

used for food

Some GMOs have health benefits

For example, maize that produces the Bt toxin has

90% less of a cancer-causing toxin than non-Bt

corn

Bt maize has less insect damage and lower

infection by Fusarium fungus that produces the

cancer-causing toxin


Widespread adoption of Bt cotton in India has led

to a 41% decrease in insecticide use and an 80%

reduction in acute poisoning cases


Possible Effects on Nontarget Organisms

Many ecologists are concerned that the growing of

GM crops might have unforeseen effects on

nontarget organisms


Addressing the Problem of Transgene Escape

Perhaps the most serious concern is the possibility

of introduced genes escaping into related weeds

through crop-to-weed hybridization

This could result in “superweeds” that would be

resistant to many herbicides


Efforts are underway to prevent this by introducing

Male sterility

Apomixis

Transgenes into chloroplast DNA (not transferred

by pollen)

Strict self-pollination


Figure 38.UN01a


Figure 38.UN01aa


Figure 38.UN01ab


Figure 38.UN01b


Figure 38.UN02

Tube

nucleus

One sperm will

fuse with the

egg, forming a

zygote (2n).

One sperm cell will fuse with the

2 polar nuclei, forming an endosperm

nucleus (3n).


Figure 38.UN03

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