1. Chapter 38: Angiosperm Reproduction and Biotechnology
Mrs. Valdes
AP Biology

2. Overview: Flowers of Deceit
Angiosperm flowers attract pollinators using visual cues and volatile chemicals
Many angiosperms reproduce sexually and asexually
Symbiotic relationships common between plants and other species
Plant breeders have genetically manipulated traits of wild angiosperm species by artificial selection

3. Concept 38.1: Flowers, double fertilization, & fruits unique features of angiosperm life cycle
Gametophytes: produce haploid (n) gametes by mitosis; fertilization of gametes produces sporophyte
Diploid (2n) sporophytes: produce spores by meiosis; grow into haploid (n) gametophytes
In angiosperms sporophyte is dominant generation AKA large plant
Gametophytes reduced in size and depend on sporophyte for nutrients
Angiosperm life cycle characterized by “three Fs”:
flowers,
double fertilization
fruits

4. Flower Structure and Function
Flowers: reproductive shoots of angiosperm sporophyte
attach to part of stem called the receptacle
consist of four floral organs: sepals, petals, stamens, and carpels
Stamen: consists of filament topped by anther with pollen sacs that produce pollen
Carpel: long style with stigma on which pollen may land
At base of style is ovary containing one or more ovules
Pistil: single carpel or group of fused carpels
Complete flowers: contain all four floral organs
Incomplete flowers: lack one or more floral organs,
Inflorescences: Clusters of flowers

5. Development of Male Gametophytes in Pollen Grains
Pollen develops from microspores within the microsporangia, or pollen sacs, of anthers
If pollination succeeds pollen grain produces pollen tube that grows down into ovary and discharges sperm near embryo sac
Pollen grain: consists of two-celled male gametophyte and spore wall

6. Development of Female Gametophytes (Embryo Sacs)
Within ovule, megaspores produced by meiosis and develop into embryo sacs, AKA female gametophytes

7. Female gametophyte (embryo sac)
Fig. 38-3
(a)
Development of a male
gametophyte (in pollen grain)
(b)
Development of a female
gametophyte (embryo sac)
Microsporangium
(pollen sac)
Megasporangium (2n)
Microsporocyte (2n)
Ovule
Megasporocyte (2n)
MEIOSIS
Integuments (2n)
Micropyle
4 microspores (n)
Surviving
megaspore (n)
Each of 4
microspores (n)
MITOSIS
Ovule
Generative cell (n)
Male
gametophyte
3 antipodal cells (n)
Figure 38.3 The development of male and female gametophytes in angiosperms
Female gametophyte
(embryo sac)
2 polar nuclei (n)
1 egg (n)
Nucleus of
tube cell (n)
Integuments (2n)
2 synergids (n)
20 µm
Ragweed
pollen
grain
Embryo
sac
75 µm
100 µm

8. Pollination Pollination: transfer of pollen from anther to stigma
can be by wind, water, bee, moth and butterfly, fly, bird, bat, or water

9. Abiotic Pollination by Wind
Fig. 38-4a
Abiotic Pollination by Wind
Figure 38.4 Flower pollination
Hazel staminate flowers
(stamens only)
Hazel carpellate flower
(carpels only)

10. Common dandelion under normal light
Fig. 38-4b
Pollination by Bees
Common dandelion under
normal light
Figure 38.4 Flower pollination
Common dandelion under
ultraviolet light

11. Anther Stigma Moth on yucca flower
Fig. 38-4c
Pollination by Moths and Butterflies
Anther
Figure 38.4 Flower pollination
Stigma
Moth on yucca flower

12. Blowfly on carrion flower
Fig. 38-4d
Pollination by Flies
Figure 38.4 Flower pollination
Fly egg
Blowfly on carrion flower

13. Hummingbird drinking nectar of poro flower
Fig. 38-4e
Pollination by Birds
Figure 38.4 Flower pollination
Hummingbird drinking nectar of poro flower

14. Long-nosed bat feeding on cactus flower at night
Fig. 38-4f
Pollination by Bats
Figure 38.4 Flower pollination
Long-nosed bat feeding on cactus flower at night

15. Double Fertilization
After landing on receptive stigma, pollen grain produces pollen tube that extends between cells of style toward ovary
Double fertilization: results from discharge of two sperm from pollen tube into embryo sac
One sperm fertilizes egg, other combines with polar nuclei triploid (3n) food- storing endosperm

16. Pollen grain Stigma Pollen tube 2 sperm Style Ovary Ovule Polar nuclei
Fig. 38-5a
Stigma
Pollen grain
Pollen tube
2 sperm
Style
Ovary
Figure 38.5 Growth of the pollen tube and double fertilization
Ovule
Polar nuclei
Micropyle
Egg

17. Ovule Polar nuclei Egg Synergid 2 sperm Fig. 38-5b
Figure 38.5 Growth of the pollen tube and double fertilization
Synergid
2 sperm

18. Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n)
Fig. 38-5c
Endosperm
nucleus (3n)
(2 polar nuclei
plus sperm)
Figure 38.5 Growth of the pollen tube and double fertilization
Zygote (2n)
(egg plus sperm)

19. Seed Development, Form, and Function
After double fertilization, each ovule develops into seed
Ovary develops into fruit enclosing seed(s)
Endosperm development:
usually precedes embryo development
endosperm stores nutrients used by the seedling
OR food reserves of the endosperm are exported to the cotyledons
Embryo Development:
first mitotic division of the zygote is transverse, splitting the fertilized egg into a basal cell and a terminal cell

20. Structure of the Mature Seed
Embryo and food supply are enclosed by hard, protective seed coat
Seed enters a state of dormancy
Embryo consists of embryonic axis attached to two thick cotyledons (seed leaves)
Below cotyledons embryonic axis is called hypocotyl and terminates in radicle (embryonic root); above cotyledons called epicotyl
Seeds of some eudicots have thin cotyledons
Monocot embryo: one cotyledon
Grasses have special cotyledon called a scutellum
Two sheathes enclose embryo of grass seed: coleoptile covering young shoot and coleorhiza covering young root

21. Seed Dormancy: An Adaptation for Tough Times
Seed dormancy increases chances that germination will occur at time and place most advantageous to seedling
Breaking of seed dormancy often requires environmental cues, like temperature or lighting changes
Germination depends on imbibition
uptake of water due to low water potential of dry seed
1- Radicle (embryonic root) emerges first
2- Shoot tip breaks through soil surface
3- Hook forms in hypocotyl, and growth pushes hook above ground
4- Hook straightens and pulls cotyledons and shoot tip up

22. Foliage leaves Cotyledon Epicotyl Hypocotyl Cotyledon Cotyledon
Fig. 38-9a
Foliage leaves
Cotyledon
Epicotyl
Hypocotyl
Cotyledon
Cotyledon
Hypocotyl
Hypocotyl
Figure 38.9a Two common types of seed germination
Radicle
Seed coat
(a) Common garden bean

23. In maize and other grasses, AKA monocots, coleoptile pushes up through soil
Foliage leaves
Coleoptile
Coleoptile
Figure 38.9b Two common types of seed germination
Radicle
(b) Maize

24. Fruit Form and Function
Fruit: develops from ovary
Protects enclosed seeds and aids in seed dispersal by wind or animals
may be classified as:
dry, if ovary dries out at maturity,
fleshy, if ovary becomes thick, soft, and sweet at maturity
Fruits are also classified by their development:
Simple: single or several fused carpels
Aggregate: single flower with multiple separate carpels
Multiple: group of flowers called an inflorescence
Accessory fruit: contains other floral parts in addition to ovaries
Fruit dispersal mechanisms include:
Water, Wind, Animals

25. Figure 38.10 Developmental origin of fruits
Stigma
Carpels
Style
Stamen
Flower
Petal
Ovary
Stamen
Stamen
Sepal
Stigma
Ovary
(in receptacle)
Ovule
Ovule
Pea flower
Raspberry flower
Pineapple inflorescence
Apple flower
Each segment
develops
from the
carpel
of one
flower
Remains of
stamens and styles
Carpel
(fruitlet)
Stigma
Sepals
Seed
Ovary
Figure Developmental origin of fruits
Stamen
Seed
Receptacle
Pea fruit
Raspberry fruit
Pineapple fruit
Apple fruit
(a) Simple fruit
(b) Aggregate fruit
(c) Multiple fruit
(d) Accessory fruit

26. Coconut Dispersal by Water Fig. 38-11a
Figure Fruit and seed dispersal
Coconut

27. Dandelion “parachute”
Fig b
Dispersal by Wind
Winged seed
of Asian
climbing gourd
Dandelion “parachute”
Figure Fruit and seed dispersal
Winged fruit of maple
Tumbleweed

28. Dispersal by Animals Barbed fruit Seeds in feces Seeds carried to
Fig c
Dispersal by Animals
Barbed fruit
Seeds in feces
Figure Fruit and seed dispersal
Seeds carried to
ant nest
Seeds buried in caches

29. Concept 38.2: Plants reproduce sexually, asexually, or both
Sexual reproduction results in offspring genetically different from parents
Asexual reproduction: results in clone of genetically identical organisms
Fragmentation: separation of parent plant into parts that develop into whole plants
very common type of asexual reproduction
In some species, parent plant’s root system gives rise to adventitious shoots that become separate shoot systems
Apomixis: asexual production of seeds from diploid cell

30. Advantages and Disadvantages of Asexual Versus Sexual Reproduction
Vegetative reproduction: Asexual reproductio
beneficial if in stable environment
clone of plants vulnerable to local extinction if environment changes
Sexual reproduction: generates genetic variation that makes evolutionary adaptation possible
Only fraction of seedlings survive

31. Mechanisms That Prevent Self-Fertilization
1- Dioecious: species with staminate and carpellate flowers on separate plants
2- stamens and carpels mature at different times OR are arranged to prevent selfing
3- Self-incompatibility: MOST COMMON; plant’s ability to reject own pollen
Researchers examine molecular mechanisms
Some plants reject pollen that has S-gene matching allele in stigma cells
Recognition of self pollen triggers signal transduction pathway leading to block in growth of pollen tube

32. Vegetative Propagation and Agriculture
Clones from cuttings
Many plants asexually reproduced from plant fragments called cuttings
Callus: mass of dividing undifferentiated cells that forms where stem is cut and produces adventitious roots
Grafting
Twig or bud grafted onto plant of closely related species or variety
Stock: provides root system
Scion: grafted onto stock
Test-tube cloning and related techniques
Plant biologists adopted in vitro methods to create and clone novel plant varieties
Transgenic plants: genetically modified (GM) to express gene from another organism
Protoplast fusion: used to create hybrid plants by fusing protoplasts, plant cells with their cell walls removed

33. Concept 38.3: Humans modify crops by breeding and genetic engineering
Humans intervened in reproduction and genetic makeup of plants for thousands of years
Hybridization: common in nature; used by breeders to introduce new genes
Maize, product of artificial selection; staple in many developing countries

34. Plant Breeding
Mutations arise spontaneously OR can be induced by breeders
Plants with beneficial mutations used in breeding experiments
Desirable traits can be introduced from different species or genera
Grain triticale derived from successful cross between wheat and rye
Wheat
Rye
Triticale

35. Plant Biotechnology and Genetic Engineering
Plant biotechnology meanings:
General sense: refers to innovations in use of plants to make useful products
Specific sense: refers to use of GM organisms in agriculture and industry
Modern plant biotechnology NOT limited to transfer of genes between closely related species or varieties of same species

36. Reducing World Hunger and Malnutrition
GM plants may increase quality and quantity of food worldwide
Transgenic crops have been developed that:
Produce proteins to defend them against insect pests
Tolerate herbicides
Resist specific diseases

37. Nutritional quality of plants being improved
“Golden Rice”: transgenic variety being developed to address vitamin A deficiencies among the world’s poor
Problem? “Being developed”

38. Reducing Fossil Fuel Dependency
Biofuels: made by fermentation and distillation of plant materials like cellulose
can be produced by rapidly growing crops

39. Issues of Human Health Concerns:
Genetic engineering may transfer allergens from gene source to plant used for food
Unforeseen effects on nontarget organisms
Possibility of introduced genes escaping into related weeds through crop-to-weed hybridization
Preventative efforts:
Male sterility
Apomixis
Transgenes into chloroplast DNA (not transferred by pollen)
Strict self-pollination

40. You should now be able to:
Describe how the plant life cycle is modified in angiosperms
Identify and describe the function of a sepal, petal, stamen (filament and anther), carpel (style, ovary, ovule, and stigma), seed coat, hypocotyl, radicle, epicotyl, endosperm, cotyledon
Distinguish between complete and incomplete flowers; bisexual and unisexual flowers; microspores and megaspores; simple, aggregate, multiple, and accessory fruit
Describe the process of double fertilization
Describe the fate and function of the ovule, ovary, and endosperm after fertilization
Explain the advantages and disadvantages of reproducing sexually and asexually
Name and describe several natural and artificial mechanisms of asexual reproduction
Discuss the risks of transgenic crops and describe four strategies that may prevent transgene escape