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Chapter 36
• Reproduction in Angiosperms
Bryophytes >450mya
360 mya
Fig. 27-4, p. 584
Lily Flower
Flower Parts
• Sepals
• cover and protect flower parts in bud
• Collectively calyx
• Petals
• Can attract animal pollinators to
flower
• Collectively corolla
• Stamens
• produce pollen grains
Flower Parts
• Each stamen consists of
• a thin stalk (filament)
• attached to a saclike structure
(anther)
• Carpel
• female reproductive unit
• carpels bear ovules (can develop into
seed)
Flower Parts
• Pistil
• a single carpel or group of fused
carpels
• Each pistil has 3 sections:
• stigma, where pollen grains land
• style, through which pollen tube
grows
• ovary, containing one or more ovules
(produces one egg)
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Female floral parts
Male floral parts
Pollen grain (each
will produce two
sperm cells)
Stigma
Style
PISTIL
(consisting
of one or
more
carpels)
Anther
STAMEN
Filament
Ovary
Ovules
(each producing
one egg cell)
Petal
Sepal
Receptacle
Peduncle
Fig. 36-1b, p. 768
Pollen
• Pollen
• forms within pollen sacs in anther
• Each pollen grain contains 2 cells
• 1 generates two sperm cells
• 1 produces a pollen tube through
which sperm cells reach the ovule
Egg
and
Pollen
Fig. 36-1a, p. 768
Eggs
• Structures formed in the ovule:
• 1 egg
• 2 polar nuclei
• several other nuclei
• Egg and polar nuclei participate in
fertilization
Pollinating Agents
• Insects
• flowers yellow or blue
• scented
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Ultraviolet Markings on
Insect-Pollinated Flowers
Pollinating Agents
• Birds
• flowers yellow, orange, or red
• no strong scent
Pollinating Agents
• Bats
• flowers with dusky white petals
• scented
Coevolution
• Reciprocal adaptation
• 2 species form interdependent
relationship affecting one another’s
evolution
Pollinating Agents
Wind
• flowers make large amounts of
pollen
• have smaller petals or no petals
Woodcock Orchid
• Mimics bees!
• Examples:
• Long tubular red flowers with large,
and long beak of hummigbirds
• Scent produced by flowers similar to
female bees
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Pollination and Fertilization
• Pollination
• transfer of pollen grains from anther
to stigma
• Fertilization
• after pollination
• fusion of gametes
Double Fertilization
Flowering Plants
• Undergo double fertilization in ovule
• Egg fuses with 1 sperm cell
• forming zygote (fertilized egg)
• zygote develops into embryo in seed
• 2 polar nuclei fuse with 1 sperm cell
• forming triploid nutritive tissue
(endosperm)
Flowering Plant Life Cycle
Embryonic Development
Embryo
• Develops in the seed
• from proembryo
• to globular embryo
• to heart stage
• to torpedo stage
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Seed Structure
Mature Seed
• Contains:
• a young plant embryo
• nutritive tissue for use during
germination: endosperm or cotyledons
(seed leaves)
• Tough, protective seed coat surrounds
seed
Relationships among . . .
• Ovules: have potential to develop into seeds
• Ovaries: have potential to develop into fruits
Simple Fruits
• Develop from a single ovary
• one carpel or several fused carpels
• Fruits: mature, ripened ovaries
• Seeds: enclosed within fruits
Aggregate Fruits
• Develop from a single flower
• with many separate ovaries
Multiple Fruits
• Develop from ovaries of many flowers
• growing in proximity on a common
axis
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Accessory Fruits
• Major part of fruit is other than ovary
tissue
Explosive Dehiscence
Seed and Fruit Dispersal
Wind, water, animals
Germination (Seed Sprouting)
• Internal factors that affect germination
or NOT
• maturity of the embryo
• presence or absence of chemical
inhibitors
• presence or absence of hard, thick
seed coats
Germination (Seed Sprouting)
Imbibition
• External environmental factors
influence germination
• Varies among species
• oxygen, water, temperature, and
light (sometimes)
• before germinating, all dry seeds
absorb water by imbibition
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Germination and Growth
Dicot
• Asexually
reproduction
in the
flowering
plants:
rhizomes,
tubers, bulbs,
corms,
stolons,
plantlets, and
suckers?
Rhizome
Adventitious
roots
• Rhizome:
A horizontal
underground
stem
•
Monocot
Tuber
Rhizome
Bulb
• A fleshy
underground
stem enlarged
for food
storage
Rhizome
Tuber
• modified
underground
bud with fleshy
storage leaves
attached to
short stem
• Auxillary bulbs
(bulbets)
Bulb
Fleshy
leaves
Stem
Adventitious
roots
Roots
Tuber
Bulb
Stolon: A horizontal aboveground stem with
long internodes
Corm
• A short,
erect
undergroun
d stem
covered by
papery
scales
• Auxillary
bulbs
continue
when
parent dies
Axillary bud
Leaf scars
Corm
(modified
stem)
New
shoot
Scale leaf
(at node)
Old corm
(last year’s)
Adventitious
roots
Corm
Adventitious
roots
Stolon
(runner)
Fig. 36-21e, p. 784
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Plantlets
• Develop on leaves with meristematic
tissue along their margins
Apomixis
• Production of seeds and fruits without sexual
reproduction
• dandelions
• citrus trees
• mango
• blackberries
• Garlic
Sexual Reproduction
• Genetic diversity
• lets individuals survive in changing
environment, exploit new
environments
• Costly: Male and female gametes must
be produced and get together!
Suckers
• Develop from roots with adventitious buds
• produce additional roots, new plants
Reproduction: Sexual or Asexual?
• Sexual reproduction
• the union of two gametes
• offspring are genetically variable
• Asexual reproduction
• offspring formed without fusion of
gametes
• offspring genetically identical to
single parent
Asexual Reproduction
• Genetic similarity
• may be advantageous if environment
is stable
• Occasionally reproduce sexually
• increasing their genetic variability
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