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Ch. 9 Flowers and Reproduction (Flower Structure and Cross-Pollination…
Ch. 9 Flowers and Reproduction
Concepts
Sexual Reproduction
offspring are genetically diverse
some offspring are more adapted, others are less
isolated individuals cannot reproduce
Asexual Reproduction
offspring are genetically identical
all offspring are equally adapted
isolated individuals can reproduce
Seeds
produced by sexual reproduction
means of long-distance dispersal
feces, wind, water
Asexual Reproduction
fragmentation
large spreading/vining plant grows to several meters
individual parts become self-sufficient
establishing adventitious roots
Sexual Reproduction
The Plant Life Cycle
haploid sex cells
sperms, eggs
gametes
syngamy, fertilization
fusion of gametes to form zygote
grows to become a new individual
sporophyte phase
sporophytes
always diploid
have organs
spores
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haploid
gametophyte
microgametophytes
from microspores
small sperm cells
megagametophytes
from megaspores
large egg
-phyte = plant, gmaeto- =produces gametes
type of life cycle
alteration of generations
life cycle with two generations
sporophyte and gametophyte
heteromorphic generations
gametophytes do not resemble sporophytes at all
Flower Structure
terms:
pedicel
flower stalk
receptacle
very end of the axis
complete flowers
have all four:
sepals, petals, stamens, and carpels
incomplete flowers
lack 1-2 basic floral appendages
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Sepals
define:
lowermost and outermost part of the four floral appendages
calyx
all sepals together
Petals
define:
above sepals, on receptacle
corolla
all petals together
perianth
sepals and petals together
Stamens
define:
"male" part of the flower
produces pollen
not really male
two parts:
filament
stalk
anther
where pollen is produced
sporophyte
microsporocyte
enlarge and undergo meiosis
produce four microspores
tapetum
layer with nurse cells
pollen
from microspores separating and forming in shape
Carpels
define:
constitute the gynoecium
highest level on the receptacle
three main parts:
stigma
catches pollen grains
style
elevates the stigma to a useful position
ovary
placentae
bear ovules
nucellus
central mass of parenchyma
megasporocytes
only one in each ovule
preperation for meiosis
Gametophytes
Microgametophyte
produces:
vegetative cell
large
generative cell
small, lens-shaped
pollen tube
penetrates into loose, open tissues of the stigma
Megagametophyte
embryo sac
term for multinucleate
central cell
seven cells:
2 polar nuclei
three antipodal cells
egg apparatus
2 synergids
egg
megagamete
Fertilization
fusions
plasmogamy
fusion of protoplasts of gametes
karyogamy
fusion of nuclei
endosperm nucleus
triploid
has three full sets of genes
double fertilization
both sperm nuclei undergo fusions
one with egg nucleus
one with polar nucleus
endosperm
all of coenocytic and cellular tissue
Embryo and Seed Development
suspensor
short stalk-like structure
puches embryo into endosperm
cotyledons
grow from two primordia
axis contains:
radicle
embryonic root
epicotyl
embryonic stem
hypocotyl
root/shoot junction
albuminous seed
mature seed where endosperm is abundant
exalbuminous
mature seed where endosperm is sparse/absent
seed coat
mature integuments that surround nucellus
Fruit Development
fruit
mature ovary
three layers
exocarp
outer layer, skin/peel
mesocarp
middle, flesh
endocarp
innermost layer, pit
pericarp
entire fruit wall
Flower Structure and Cross-Pollination
Cross-Pollination
define:
pollination of a carpel by pollen from a different individual
self-pollination
#
pollination of a carpel by pollen from same flower
or another flower on same plant
Stamen and Style Maturation Times
self-fertilization in flowers that have both stamens and carpels
is prevented if anthers and stigmas mature at different times
Ex: mature anthers release pollen but stigma is not mature
Stigma and Pollen Incompatibility
compatibility barriers
chemical reactions between pollen and carpels
prevent pollen growth
Monoecious and Dioecious Species
organs
essential
produce critically important spores
nonessential
sepals and petals
flowers
imperfect
lack essential organs, incomplete
perfect
is complete and has essential organs
dioecy
dioecious
some produce only staminate flowers, others only produce carpellate flowers
monoecy
monoecious
having staminate flowers located on same plant as carpellate flowers
Animal-Pollinated Flowers
coevolution
flower becoming adapted to insect visitation
insect efficient exploitation of the flower
actinomorphic
radially symmertrical
zygomorphic
bilaterally symmetrical
Wind-Pollinated Flowers
grasses, oaks, hickories, all conifers
wind carries pollen to fertilize
Ovary Position
inferior ovary
epigynous
sepals fuse and thick, protective layer around ovary
superior ovary
hypogynous parts
no fusion occurs
intermediate ovary
half-inferior with perigynous flower parts
Inflorescences and Pollination
inflorescence
many flowers grouped together
give collective visual signal to pollinators
two basic arrangements of inflorescence
determinate inflorescences
limited potential for growth b/c flower
indeterminate inflorescences
lowest/outermost flowers open first
Fruit Types and Seed Dispersal
True Fruits and Accessory Fruits
true fruit
fruits containing only ovarian tissue
accessory fruit
false fruit
any nonovarian tissue is present
simple fruit
fruit develops from a single ovary
fused ovaries of one flower
most common kind
aggregate fruit
separate carpels of one gynoecium fuse during development
multiple fruit
all individual fruits of an inflorescence fuse onto one fruit
Classification of Fruit Types
dry/fleshy
dry = not typically eaten by natural seed-distributing animals
fleshy = are eaten by natural seed-distributing animals
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dehiscent fruits
break open and release seeds
indehiscent fruits
do not break open and release seeds
spore grows into
appendages
inhibited by
most fleshy fruits are
