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Chapter 9: Flowers and Reproduction (Flower Structure and Cross…
Chapter 9: Flowers and Reproduction
Asexual Reproduction
fragmentation = several self sufficient parts
common in cacti
numerous methods
Sexual Reproduction
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Flower Structure
Sepals
thick
tough
lowermost and outermost floral appendage
waxy
all sepals = calyx
Petals
on receptacle
all petals = corolla
sepals + petals = perianth
attract correct pollinators
not typically in wind pollinated plants
Stamens
all stamens = androecium
two parts
anther = pollen
filament = stalk
microsporocytes
undergo meiosis
produce four microspores
microspore mother cells
tapetum = nurse cells
Carpels
gynoecium
highest level on receptacle
parts
style = elevates stigma
ovary = megaspore produced
stigma = catches pollen
placentae
inside ovary
bear ovules
have nucellus
short stalk
pedicel = flower stalk
receptacle = end of flower axis
floral appendages
stamens
carpels
petals
sepals
complete flowers = ALL
incomplete flowers = lack one or two
Gametophytes
Megagametophytes
develop from megaspores
embryo sac = multinucleate megagametophyte
seven cells
one large central cell
two polar nuclei
three small antipodal cells
egg aparatus
one egg
two synergids
Microgametophytes
develop from microspores
mitotic division
generative cell
vegetative cell
two sperm cells
pollen grain lands on stigma and germinates
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penetrates stigma
pollen tube is produced
protected and nourished by style
The Plant Life Cycle
gametophyte stage
undergo syngamy ---> zygote ---> diploid sporophyte
gametophyte
new haploid plant
from spores
gametophytes
microgametophytes
sperm
male
microspores
megagametophytes
egg
female
megaspores
sporophyte stage
sporophyte generation
one phase of life
sporophytes = diploid
spores
haploid
plant gametes
mitosis
Mammal life cycle
gametes
eggs
sperm
syngamy or fertilization
zygote
diploid
fertilized egg
simple
Fertilization
second sperm nucleus into central cell
syngamy
karyogamy = fusion of nuclei
plasmogamy
fusion of gametes
fusion of protoplasts
endosperm nucleus
three full sets of genes
triploid
double fertilization
one sperm fuses with egg
one sperm fuses with polar nuclei
endosperm = all tissue
cellular
coenocytic
Fruit Development
fruit = mature ovary
layers = pericarp
exocarp = outer, skin or peel
mesocarp = middle, flesh
endocarp = innermost, stone or pit
Flower Structure and Cross-Pollination
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Cross-Pollination
self = pollination by own plant
cross = pollination of carpel by other individual
genetics
mutations = new genes
cross pollination = lots of new genes
self pollination decreased and cross pollination increased
Stamen and Style Maturation Times
anthers and stigma mature differently
not effective for ensuring cross pollination
pollination effected by young flowers
Stigma and Pollen Incompatibility
compatibility barriers inhibit self pollination
pollen growth prevented
diploid = greater chance of pollen rejection
Monoecious and Dioecious Species
essential organs
stamens
carpels
imperfect flowers = miss essential organs
perfect flowers
have essential organs
may lack petals or sepals
nonessential organs
petals
sepals
staminate/ carpellate flowers
monoecy
same plant
monoecious
dioecy
dioecious
different plants
Animal-Pollinated Flowers
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evolution of flowering plants
wind pollination has low probability rate
coevolution = flower adapted for visitation
flower shape
symmetrical/regular/actinomorphic
bilaterally symmetrical/zygomorphic
Wind-Pollinated Flowers
added by growth pattern
not widely scattered individuals
no need to attract pollinators
Ovary Position
superior = hypogynous
inferior = epigynous
half - inferior = perigynous
Inflorescenes and Pollination
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inflorescence
many flowers grouped together
signal pollinators
arrangements
determinate inflorescences
terminal flower opens first
limited growth potential
indeterminate inflorescences
lowest flowers open first
new flowers initiated at apex
Fruit Types and Seed Dispersal
True Fruits and Accessory Fruits
types
accessory fruit
true fruit
simple fruit
aggregate fruit
multiple fruit
Classification of Fruit Types
fruit opening
Dehiscent fruits
indehiscent fruots
Embryo and Seed Development
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zygote
suspensor = short stalked structure
embryo proper
end of embryo = 2 cotyledons
torpedo stage
radicle = embryonic root
epicotyl = embryonic stem
hypocotyl = root/shoot junction
seeds
exalbuminous = sparse endosperm
albuminous = abundant endosperm
seed coat or testa = integuments surround nucellus
