Ch. 38 Angiosperm Reproduction and Biotechnology

Objectives:

L.O. 2.31 The student can connect concepts in and across domains to show that timing and coordination of specific events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.L.O. 2.32 TSIAT use a graph or diagram to analyze situations or solve problems (quantitatively or qualitatively) that involve timing and coordination of events necessary for normal development in an organism.L.O. 2.33 TSIAT justify scientific claims with scientific evidence to show that timing and coordination of several events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms.L.O. 2.34 TSIAT describe the role of programmed cell death in development and differentiation, the reuse of molecules, and the maintenance of dynamic homeostasis.L.O. 2.35 TSIAT design a plan for collecting data to support the scientific claim that the timing and coordination of physiological events involve regulation.L.O. 2.36 TSIAT justify scientific claims with evidence to show how timing and coordination of physiological events involve regulation.L.O. 2.37 TSIAT connect concepts that describe mechanisms that regulate the timing and coordination of physiological events.

38.1 Flowers, Double Fertilization, and Fruits are Unique Features of the Angiosperm Life Cycle

• Alteration of generations– Multicellular haploid (n) gametophyte and diploid

(2n) generations sporophyte.Key

Haploid (n)

Diploid (2n)

Gametes

MEIOSIS FERTILIZATION

Zygote

MitosisDiploidmulticellularorganism

(a) Animals

n

n

n

2n 2n 2n2n

n n

n

n n

MEIOSIS FERTILIZATION

Mitosis Mitosis

Mitosis

GametesSpores

Zygote

Haploid multi-cellular organism(gametophyte)

Diploidmulticellularorganism(sporophyte)

(b) Plants and some algae

Flower Structure and Function• Flowers are angiosperm’s reproductive organ system.• Flowers’ size, shape, color, odor, organ arrangement, and time of opening are largely influenced by the type of pollinator.

StamenAnther

Filament

Petal

Receptacle

Stigma

StyleOvary

Carpel

Sepal

(a) Structure of anidealized flower

Simplified angiospermlife cycle

(b)

Key

Haploid (n)

Diploid (2n)

Anther

Pollen tube

Germinated pollen grain (n)(male gametophyte)

Ovary

OvuleEmbryo sac (n)(female gametophyte)

Egg (n)

Sperm (n)

FERTILIZATION

Zygote(2n)

Mature sporophyteplant (2n)

Germinatingseed

Seed

Seed

Simplefruit

Embryo (2n)(sporophyte)

© 2011 Pearson Education, Inc.

Video: Flower Plant Life Cycle (time lapse)

Pollination• Transfer of pollen from an anther to a stigma.

– Wind (grasses and trees)– Water (aquatic plants)– Animals; insects, birds, etc.

Abiotic Pollination by Wind Pollination by Bees

Hazel staminate flowers(stamens only)

Hazel carpellateflower (carpels only)

Common dandelionunder normal light

Common dandelion underultraviolet light

Pollination by Mothsand Butterflies

Blowfly on carrionflower

Pollination by Flies Pollination by Bats

Moth on yucca flower Long-nosed bat feedingon cactus flower at night

Hummingbirddrinking nectar ofcolumbine flower

Pollination by Birds

Stigma

AntherMoth

Fly egg

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Video: Bee Pollinating

© 2011 Pearson Education, Inc.

Video: Bat Pollinating Agave Plant

Coevolution• The evolution of interacting

species in response to changes in 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

– Ex: Darwin correctly predicted a moth with a 28 cm long tongue based on the morphology of a particular flower

Development of Male Gametophytes in Pollen Grains

• Each anther has 4 microsporangia (pollen sacs)

• Within this are microsporocytes (2n similar to animal follicle)

• These undergo meiosis producing microspores.

• These undergo mitosis producing 2 cells (pollen):– Generative: forms 2 sperm– Tube: used to transfer sperm to

ovule

Microsporangium(pollen sac)

Microsporocyte

Microspores (4)

Each of 4microspores

Generative cell(will form 2 sperm)

(LM)75 m

20 m

MEIOSIS

MITOSIS

Male gametophyte(in pollen grain)

Nucleus of tube cell

Ragweed pollen grain(colorized SEM)

Key to labels

Haploid (n)

Diploid (2n)

Development of Female Gametophytes (embryo sac)

• Occurs within the megasporangium.

• The megasporocyte undergoes meiosis making megaspores.

• This undergoes mitosis (w/o cytokinesis) making a large cell with 8 nuclei. This is the embryo sac.

(b) Development of a female gametophyte (embryo sac)

100

m

MEIOSIS

MITOSIS

Key to labels

Haploid (n)

Diploid (2n) (LM)

Embryo sac

Ovule

Megasporangium

Megasporocyte

Integuments

Micropyle

Survivingmegaspore

Antipodal cells (3)

Polar nuclei (2)

Egg (1)

Synergids (2)

Ovule

Integuments

Fem

ale gam

etop

hyte

(emb

ryo sac)

Double Fertilization• When pollen reaches the stigma, the tube forms, grow

down the style to the micropyle (hole in the underside of the embryo sac).

• Each sperm has a job:1. Fertilizes the egg2. Combines with polar bodies making a triploid nucleus in a

large cell endosperm (food storing tissue for seed)

Stigma

Pollentube

2 31

2 sperm

StyleOvary

Ovule

Micropyle

Pollengrain

Polarnuclei

Egg

Ovule

Polarnuclei

Egg

Synergid

2 sperm

Endospermnucleus (3n)(2 polar nucleiplus sperm)

Zygote(2n)

© 2011 Pearson Education, Inc.

Animation: Seed DevelopmentRight-click slide / select “Play”

Seed Development, Form, and Function• Endosperm develops as a food source (carbohydrates storage)• The embryo divides into a basal cell (anchor) and terminal cell

(embryo) and cotyledon forms (another food supply)• Seed dehydrates entering dormancy.

– This is an adaptation for when environmental conditions are right for imbibition (uptake of water to start germination)..

Ovule

EndospermnucleusInteguments

Zygote

Zygote

Terminal cellBasal cell

Proembryo

Suspensor

Basalcell

Cotyledons

Shootapex

Rootapex

SuspensorSeedcoat

Endosperm

Fruit Form and Function• Fruit is the ovary of the flower which protects

and aids in dispersal of the seed.• Types of fruit:

Stamen Ovary

Stigma

OvulePea flower

Seed

Pea fruit

(a) Simple fruit: 1 carpel (b) Aggregate fruit: many carpels

(c) Multiple fruit:Many flowers

(d) Accessory fruit: carpel is the core,The flesh is the receptable.

Carpels Stamen

Raspberry flower

Carpel(fruitlet)

Stigma

Ovary

Stamen

Raspberry fruit

Flower

Pineappleinflorescence

Each segmentdevelopsfrom thecarpelof oneflower

Pineapple fruit

Stigma

PetalStyle

StamenSepal

OvuleOvary (in

receptacle)

Apple flower

Remains ofstamens and styles

Sepals

SeedReceptacle

Apple fruit

Seed DispersalDispersal by Wind

Dandelion “seeds” (actually one-seeded fruits)

Winged fruit of a maple

Dandelion fruitTumbleweed

Dispersal by Water

Winged seed ofthe tropical Asian

climbing gourdAlsomitra macrocarpa

Coconut seed embryo,endosperm, and endocarp

inside buoyant husk

Seed DispersalDispersal by Animals

Fruit of puncture vine(Tribulus terrestris)

Squirrel hoardingseeds or fruitsunderground

Ant carryingseed with nutritious“food body” to itsnest

Seeds dispersed in black bear feces

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Animation: Fruit Development Right-click slide / select “Play”