Chapter 27 : Plant Kingdom:
Seed Plants
Seeds
• Multicellular young plant with embryonic
root, stem and its leaves
• Develop from fertilized egg, female
gametophyte and its tissues
• Protected by seed coat
• Embryonic sporophyte
Gymnosperms and Angiosperms bear
seeds
• Seed develops from ovule (megasporangium
and its enclosed structures)
• Layers of sporophyte tissue surrounding and
enclosing megasporangium make the
integuments
• Seed coat develops from integuments after
fertilization
Fig. 30-3-1
Integument
Spore wall
Immature
female cone
Megasporangium
(2n)
Megaspore (n)
(a) Unfertilized ovule
Gymnosperms and Angiosperms
• Vascular tissue
– Xylem and phloem
• Alternation of generations
– Dominant sporophyte, gametophyte reduced
• No free-living gametophytes
– Dependent on sporophyte
• All heterosporous: microspores and
megaspores
Gymnosperms
• “naked seed”
• Pine, spruce, fir, hemlock, Gingko
• 4 phyla
– Coniferophyta – conifers
– Gingkophyta – gingko
– Cycadophyta – cycads
– Gnetophyta – gnetophytes (unusual)
Conifers
•
•
•
•
Pine, spruce, fir, hemlock
Most familiar
Woody
Produce annual secondary tissue (wood
+bark)
• Wood (secondary xylem)
– Tracheids – long, tapering cells with pits; water
and dissolved nutrient minerals move between
cells
Fig. 30-5h
Douglas fir
Fig. 30-5i
European larch
Fig. 30-5j
Bristlecone pine
Fig. 30-5k
Sequoia
Fig. 30-5l
Wollemi pine
Fig. 30-5m
Common juniper
Resin – produced by conifers
•
•
•
•
Viscous, clear
Protection – insects, fungi
Collects in resin ducts (roots, stems, leaves)
Produced and secreted by cells lining resin
ducts
Needles - conifers
• Long, narrow, tough, leathery
• Pines – clusters; 2-5 needles
• American arborvitae – scalelike and cover
stem
• Most evergreen
• Few deciduous – Dawn redwood, larch, bald
cypress
Conifers continued
• Most monoecious – separate male and female
reproductive parts – different locations, same
plant
• Parts borne in strobili called cones
Ecological importance
• Food and shelter – animals
• Roots – hold soil, prevent erosion
• Wood – building, paper, medicine, turpentine,
resins
• Landscape design – trees, wreaths
Pines
• Pine tree – mature sporophyte
• Heterosporous – microspores and megaspores
produced in separate cones
– Male cones - < 1 cm; lower branches; spring
– Female cones – woody; familiar; year round;
upper branches; bear seeds; vary in size
Male cone (pollen cone)
• Composed of sporophylls = leaflike structures –
bear sporangia on underside
• Base of each sporophyll = 2 microsporangia
(contain numerous sporocytes)
• Each microsporocyte  meiosis  4 haploid
microspores  reduced male gametophyte
(pollen grain)
• Each pollen grain: 4 cells + 2 large air sacs
(buoyancy , wind)
– 1- generative cell
– 1- tube cell
– 2 - degenerate
Male Pine Pollen Cone
Pine Pollen Cone
Female cone (seed cone)
• Each cone scale – 2 megaporangia on upper
surface
• Megasporangium 
meiosismegasporocyte 4 haploid
megaspores
• 1 megaspores  mitosis  female
gametophyte  egg
• Other 3 cells degenerate
Female Pine Cones
Pine Ovulate Cone
Pine Ovule
Pollination
• Pollen to female cones
• Spring - week to 10 days
– Then pollen cones wither and drop
• Pollen grains adhere to sticky surface
(produced by ovule when ready)
Conifer adaptation
• Eliminate need for external water for sperm
transport
• Instead  air and pollen tube
Fig. 30-6-4
Key
Haploid (n)
Diploid (2n)
Ovule
Ovulate
cone
Pollen
cone
Megasporocyte (2n)
Integument
Microsporocytes
(2n)
Megasporangium
Pollen (2n)
Pollen grain
grains (n) MEIOSIS
MEIOSIS
Mature
sporophyte
(2n)
Microsporangia
Microsporangium (2n)
Seedling
Archegonium
Female
gametophyte
Seeds
Food
reserves
(n)
Seed coat
(2n)
Embryo
(2n)
Sperm
nucleus (n)
Pollen
tube
FERTILIZATION
Egg nucleus (n)
Surviving
megaspore (n)
Cycads
•
•
•
•
•
•
Phylum Cycadophyta
Seed cones ; compound leaves
Important Triassic period
Tropical
Resemble palms
Lifecycle like pines BUT
– Dioecious (seed cones – female plants; pollen
cones – male plants)
– Motile sperm cells
Fig. 30-5a
Cycas revoluta
Gingkoes
•
•
•
•
•
•
•
Phylum Gingkophyta
Single living species – Gingko biloba
China and Japan
Resistant air pollution  cities
Deciduous
Dioecious, flagellated sperm, no cones
Female trees – fleshy seed covering  rancid
butter
• Medicinal – neurological function; memory
Fig. 30-5b
Ginkgo biloba
pollen-producing tree
Fig. 30-5c
Ginkgo biloba
leaves and fleshy seeds
Gnetophytes
• Phylum Gnetophyta
• More advanced
– Vessel elements in xylem
– Cone clusters resemble flower clusters
– Lifecycle resembles angiosperms
• 3 genuses – Genus Ephedra - ephedrine
Fig. 30-5d
Gnetum
Fig. 30-5e
Ephedra
Fig. 30-5f
Welwitschia
Fig. 30-5g
Ovulate cones
Welwitschia
Angiosperms
• Phylum Anthophyta
• “seed enclosed in a case or vessel” (fruit) –
ovules are protected
• Flowering (sexual reproduction) – double
fertilization
• Vascular - vessel elements; sieve tube
members
• Most successful – almost every habitat
• Corn, oak, lilies, cacti, apples, grass, palms
Angiosperm importance
•
•
•
•
•
Food crops – our survival
Wood – lumber
Fibers – cotton, linen
Medicine – codeine
Products – rubber, tobacco, coffee, chocolate,
aromatic oils
2 classes of Angiosperms :
Monocots and Dicots
• Monocotyledones – palms, grasses, orchid,
iris, onion, lilies
• Mostly herbaceous
• Long, narrow leaves – parallel veins
• Flower parts – 3’s
• Single cotyledon
• Endosperm present
Fig. 30-13e
Orchid
Fig. 30-13e1
Pygmy date palm (Phoenix roebelenii)
Fig. 30-13f
Fig. 30-13g
Barley
Anther
Stigma
Ovary
Filament
• Dicotyledones – oaks, roses, mustards, cacti,
blueberries, sunflowers
• More diverse
• Herbaceous or woody
• Leaves vary in shape (broader) – netted veins
• Flower parts - 4’s or 5’s
• 2 cotyledons
• Endosperm absent
Fig. 30-13h
California poppy
Fig. 30-13i
Pyrenean oak
Fig. 30-13j
Dog rose
Fig. 30-13k
Snow pea
Fig. 30-13l
Zucchini flowers
7 ways monocots and dicots differ
•
•
•
•
•
•
•
Leaf venation
Vascular bundles
Cotyledon #
Flower parts - #
Endosperm present?
Cambium present?
Roots
Fig. 30-13n
Monocot
Characteristics
Eudicot
Characteristics
Embryos
Two cotyledons
One cotyledon
Leaf
venation
Veins usually
parallel
Veins usually
netlike
Stems
Vascular tissue
scattered
Vascular tissue
usually arranged
in ring
Fig. 30-13o
Monocot
Characteristics
Eudicot
Characteristics
Roots
Taproot (main root)
usually present
Root system
usually fibrous
(no main root)
Pollen
Pollen grain with
one opening
Pollen grain with
three openings
Flowers
Floral organs
usually in
multiples of three
Floral organs usually
in multiples of
four or five
Flowers and Sexual Reproduction
Fig. 30-7
Stigma
Stamen
Anther
Carpel
Style
Filament
Ovary
Petal
Sepal
Ovule
Fig. 30-10-4
Key
Haploid (n)
Diploid (2n)
Mature flower on
sporophyte plant
(2n)
Microsporangium
Microsporocytes (2n)
Anther
MEIOSIS
Ovule (2n) Microspore
(n)
Ovary
Germinating
seed
MEIOSIS
Megasporangium
(2n)
Embryo (2n)
Endosperm (3n)
Seed
Seed coat (2n)
Nucleus of
developing
endosperm
(3n)
Male gametophyte
(in pollen grain)
Pollen
(n)
grains
Stigma
Pollen
tube
Megaspore
(n)
Antipodal cells
Female gametophyte Central cell
(embryo sac)
Synergids
Egg (n)
Generative cell
Tube cell
Sperm
Style
Pollen
tube
Sperm
(n)
FERTILIZATION
Zygote (2n)
Egg
nucleus (n)
Discharged sperm nuclei (n)
Fig. 38-3
(b) Development of a female
gametophyte (embryo sac)
(a) Development of a male
gametophyte (in pollen grain)
Microsporangium
(pollen sac)
Megasporangium (2n)
Microsporocyte (2n)
Ovule
MEIOSIS
Megasporocyte (2n)
Integuments (2n)
Micropyle
4 microspores (n)
Surviving
megaspore (n)
Generative cell (n)
MITOSIS
Male
gametophyte
Ovule
3 antipodal cells (n)
2 polar nuclei (n)
Nucleus of Integuments (2n)
tube cell (n)
1 egg (n)
2 synergids (n)
75 µm
Ragweed
pollen
grain
100 µm
20 µm
Embryo
sac
Female gametophyte
(embryo sac)
Each of 4
microspores (n)
Fig. 38-5a
Stigma
Pollen grain
Pollen tube
2 sperm
Style
Ovary
Ovule
Polar nuclei
Micropyle
Egg
Fig. 38-5b
Ovule
Polar nuclei
Egg
Synergid
2 sperm
Fig. 38-5c
Endosperm
nucleus (3n)
(2 polar nuclei
plus sperm)
Zygote (2n)
(egg plus sperm)
Pollen Grains - SEM
Pollination
• Self-pollination – same flower or different
flower on same plant
• Cross-pollination – pollen to another flower
on another individual (same species)
– Advantage – genetic variation
Ways to prevent Self-pollination
• Separate male and female individuals
– Pistillate and Staminate flowers
• Pollen shed before or after stigma receptive
• Self-incompatibility – genetic
– Pollen can’t cause fertilization in same or other
flowers on same plant
– Usually inhibit pollen tube
Fig. 38-13
(a) Sagittaria latifolia staminate flower (left) and carpellate
flower (right)
Stamens
Styles
Thrum flower
(b) Oxalis alpina flowers
Styles
Stamens
Pin flower
Animal Pollination
• Bees – blue or yellow flowers
• Carrion plant – reeking flesh smell – flies
transfer pollen when looking to lay eggs
• Hummingbirds – red, yellow, orange – no
scent
• Bats – flower open at night; dull white;
fermenting fruit smell
• Orchids – resemble female bees – color,
shape, scent
Fig. 38-1
Fig. 38-4b
Pollination by Bees
Common dandelion under
normal light
Common dandelion under
ultraviolet light
Fig. 38-4c
Pollination by Moths and Butterflies
Anther
Stigma
Moth on yucca flower
Fig. 38-4d
Pollination by Flies
Fly egg
Blowfly on carrion flower
Fig. 38-4e
Pollination by Birds
Hummingbird drinking nectar of poro flower
Fig. 38-4f
Pollination by Bats
Long-nosed bat feeding on cactus flower at night
Wind Pollination
•
•
•
•
Grasses, ragweed, maples, oaks
Small flowers
Much pollen – higher chance
Sometimes large stigma – trap pollen
Fig. 38-4a
Abiotic Pollination by Wind
Hazel staminate flowers
(stamens only)
Hazel carpellate flower
(carpels only)
Seed and Fruit Development
•
•
•
•
FIRST
Pollination
Tube cell  pollen tube
2 sperm – down tube, enter ovule  double
fertilization  endosperm + embryo
• Ovule  seed
• Ovary  fruit
Seeds
• Embryonic plant + food
– Radicle
– Embryonic shoot
– Cotyledons
– hypocotyl
• Seed coat (from integuments)
• Inside fruit
Fig. 38-8
Seed coat
Epicotyl
Hypocotyl
Radicle
Cotyledons
(a) Common garden bean, a eudicot with thick cotyledons
Seed coat
Endosperm
Cotyledons
Epicotyl
Hypocotyl
Radicle
(b) Castor bean, a eudicot with thin cotyledons
Scutellum
(cotyledon)
Pericarp fused
with seed coat
Coleoptile
Endosperm
Epicotyl
Hypocotyl
Coleorhiza
(c) Maize, a monocot
Radicle
Fig. 38-8a
Seed coat
Epicotyl
Hypocotyl
Radicle
Cotyledons
(a) Common garden bean, a eudicot with thick cotyledons
Fig. 38-8b
Seed coat
Endosperm
Cotyledons
Epicotyl
Hypocotyl
Radicle
(b) Castor bean, a eudicot with thin cotyledons
Fig. 38-8c
Scutellum
(cotyledon)
Pericarp fused
with seed coat
Coleoptile
Endosperm
Epicotyl
Hypocotyl
Coleorhiza
(c) Maize, a monocot
Radicle
Fig. 38-9
Foliage leaves
Cotyledon
Epicotyl
Hypocotyl
Cotyledon
Cotyledon
Hypocotyl
Hypocotyl
Radicle
Seed coat
(a) Common garden bean
Foliage leaves
Coleoptile
Coleoptile
Radicle
(b) Maize
Fruits
• Mature ovary, develops around seeds
• Protection, dispersal
Types of Fruit
• Simple fruit – fleshy or dry, develops from
single pistil
– Berry – fleshy – few/many seeds
• Blueberries, grape, cranberry, banana, tomato
– Drupe – fleshy – hard, stony pit around single seed
• Peaches, plums, olives, avocados, almonds
– Follicle – dry – splits open along suture, releasing
seeds
• milkweed
– Legume – dry – splits open along 2 sutures
• Pea pods, green beans
– Capsule – dry – splits open along many sutures
• Iris, poppy, cotton
– Grains – dry – don’t split open; each grain single seed;
seed coat fused to fruit wall
• Corn, wheat
– Achene – similar to grain, BUT seed coat NOT fused to
fruit wall, so becomes separated from seed
• sunflower
– Nuts – dry – stony wall – don’t split at maturity
• Chestnuts, acorns, hazelnuts
More Fruit types
• Aggregate fruits – from single flower with many
separate carpels
– After fertilization, each ovary from each carpel enlarges
(may fuse together to form single fruit)
• Raspberries, blackberries, magnolia fruits
• Multiple fruits – ovaries of many flowers grow
close on common floral stalk
– Ovary from each flower fuses as develops and
enlarges after fertilization
• Pineapples, figs, mulberries
• Accessory fruits – ovary + other plant tissues
make fruit
– Strawberry = receptacle
– Apple/pear – outer part = enlarged floral tube of
receptacle and part of calyx
Fig. 38-10
Carpels
Stamen
Flower
Petal
Stigma
Style
Ovary
Stamen
Stamen
Sepal
Stigma
Pea flower
Ovule
Ovary
(in receptacle)
Ovule
Raspberry flower
Carpel
(fruitlet)
Seed
Stigma
Ovary
Pineapple inflorescence
Each segment
develops
from the
carpel
of one
flower
Apple flower
Remains of
stamens and styles
Sepals
Stamen
Seed
Receptacle
Pea fruit
(a) Simple fruit
Raspberry fruit
(b) Aggregate fruit
Pineapple fruit
(c) Multiple fruit
Apple fruit
(d) Accessory fruit
Fig. 30-8
Tomato
Ruby grapefruit
Nectarine
Hazelnut
Milkweed
Seed Dispersal
• Wind –
– winged fruits – maple
– Light, feathery plumes – dandelion, milkweed
• Animals –
– Spines/barbs – burs
– Eaten – fleshy
– Animals bury – squirrels, ants
• Water
– Coconut – air spaces - float
• Explosive dehiscence
– Fruit bursts open suddenly and violently
– Seeds forcibly discharged
– Pressure differences in turgor or drying out
– Touch-me-not; bitter cress
Fig. 30-9
Wings
Seeds within berries
Barbs
Fig. 38-11a
Dispersal by Water
Coconut
Fig. 38-11b
Dispersal by Wind
Winged seed
of Asian
climbing gourd
Dandelion “parachute”
Winged fruit of maple
Tumbleweed
Fig. 38-11c
Dispersal by Animals
Barbed fruit
Seeds carried to
ant nest
Seeds in feces
Seeds buried in caches
Flowering Plant Adaptations
• Seed production
• Closed carpels, fruits, double fertilization
(increase reproductive success)
• Interdependencies with insects
– Dispersal, mixing genes
• Vessel elements – xylem
•
•
•
•
•
Sieve tube members – phloem
Larger leaves – light
Abscission – reduce water loss
Stems/roots – food storage
Adaptability of sporophyte
– Dry vs. wet environment
Asexual reproduction in Flowering
Plants
• Asexual
– No flower, seeds, fruits
– Vegetative parts expand – separate from rest of
plant
– Stems, roots, leaves
– 1 parent  no meiosis, fusion of gametes
– Genetically identical to parent
Asexual methods
• Rhizome
– Horizontal underground stem; branches
– Branches separate  new plants
– Iris, bamboo, ginger, some grasses
• Tubers
– Fleshy, underground stem – food storage
– Parent dies and tuber forms new plant
– Potatoes – “eyes”
• Bulb
– Underground bud – fleshy; storage leaves attached to
short stem
– Round, covered with paper-like bulb scales
– Lilies, tulips, onions, daffodils
• Corm
– short, erect, underground stem; storage stem
– Crocus, gladiolus, cyclamen
• Stolon (runners)
– Horizontal, aboveground stem; along surface
– Buds develop on stolon  new shoot that roots
– Strawberry
• Apomixis - asexual
– Flowering plant produces embryos in seeds, but
NO MEIOSIS/fusion of gametes
– Garlic, dandelions, blackberries, citrus trees
You should now be able to:
1. Explain why pollen grains were an important
adaptation for successful reproduction on land
2. List and distinguish among the four phyla of
gymnosperms
3. Describe the life history of a pine; indicate which
structures are part of the gametophyte generation
and which are part of the sporophyte generation
You should now be able to:
4. Identify and describe the function of the following
floral structures: sepals, petals, stamens, carpels,
filament, anther, stigma, style, ovary, and ovule
5. Explain how fruits may be adapted to disperse
seeds
6. Diagram the generalized life cycle of an
angiosperm; indicate which structures are part of
the gametophyte generation and which are part of
the sporophyte generation
3. Distinguish between complete and incomplete
flowers; bisexual and unisexual flowers;
microspores and megaspores; simple,
aggregate, multiple, and accessory fruit
4. Describe the process of double fertilization
5. Describe the fate and function of the ovule,
ovary, and endosperm after fertilization
6. Name and describe several natural and artificial
mechanisms of asexual reproduction