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Chapter 9: Flowers and Reproduction (Flower Structure and Cross…
Chapter 9: Flowers and Reproduction
Concept
reproduction serve two different function
produce offspring have identical copies of parental genes
generating new individuals are genetically different from the parents
with asexual reproduction
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progeny are never more fit than the parent
but during sexual reproduction
sex cells of one plant combine with those of one or several others
result in many new gene combinations
sexual reproduction
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have negative aspects
two individuals are required
sex cells must move from one plant to another
seeds
produced by sexual reproduction
often have a means of long-distance dispersal
strawberries are eaten&the seeds later defecated
bamboo fruits&seends are carried by winds
Asexual Reproduction
fragmentation
large spreading /vining plant grows to several meters in length
individual parts become self-sufficient by establish adventitious roots
within angiosperms
numerous methods of asexual reproduction have evolved
Sexual Reproduction
The Plant Life Cycle
gametes
diploid adults have sex organs that produce haploid sex cell
either sperms/eggs
by meiosis
sporophyte phase/sporophyte generation
just one phase of the plant life cycle
trees
shrubs
herbs
sporophytes
always diploid
like most adult animals
have organs with cells in haploid of undergoing meiosis
syngamy/fertilization
gametes can fuse with other gametes in a process
produce the diploid zygote
Flower Structure
pedicel
flower stalk
very end of the axis
the other flower part are attached
receptacle
complete flowers
sepals
petals
stamens
carpels
incomplete flowers
not uncommon for flowers of certain species to lack one /two of the four basic floral appendages
flowers of
Begonia
Gametophytes
microgametophyte
produce a large vegetative cell
microspores develop into micrgametophytes
divides mitotically
small lens-shaped generative cell
subsequently divides&forms two sperm cells
Fertilization
plasmogamy
syngamy of sperm&egg involved both
fusion of the protoplasts of gametes
karyogamy
fusion of the nuclei
endosperm
both coenocytic and cellular
nourishes forms as much endosperms as a zygote
Embryo and Seed Development
suspensor
which pushes the embryo deep into the endosperm
usually delicate&ephemeral in angiosperms
crushed by the later growth of embryo¬ easily detectable in a mature seed
in torpedo stage, the embryo is elongate cylinder
short axis is establushed
consisting of radicle
embryonic root
epicotyl
embryonic stem
hypocotyl
the root/shoot junction
Fruit Development
exocarp
outer layer
skin or peel
mesocarp
middle layer
flesh
innermost layer
pericarp
entire fruit wall
composed of one, two or all three layers
Flower Structure and Cross-Pollination
Cross-Pollination
pollination of a carpel by pollen from a different individual
self-pollination
pollination of a carpel by pollen from the same flower or another flower on the same plant
Stamen and Style Maturation Times
self-fertilization in flowers have both stamens and carpels is prevented if anthers&stigmas mature at different times
Stigma and Pollen Incompatibility
compatibility barriers
self-pollination is inhibited
chemical reactions between pollen&carpels that prevent pollen growth
Monoecious and Dioecious Species
imperfect flowers
flowers lack either or both essential organs are not only incomplete
perfect flower
even though it may lack either sepals/petals or both
nonessential organs
sepals and petals do not produce spores
monoecy
condition of having staminate flowers located on the same plants as carpellate flowers
monoecious
species include cattails and corn
ears are clusters of fertilized carpellate flowers
tassels bear numerous staminate flowers
Animal-Pollinated Flowers
had dramatic impact on the evolution of flower plant
coevolution
flower become adapted for visitation by a particular insect
the insect for efficient exploitation of the flower
actinomorphic/regular
stems and root
most flowers are radially symmetrical
any longitudinal cut through the middle produces two halves that are mirror images of each other
zygomorphic
flowers and pollinators have coevolved is such a way that the flowers are now also bilaterally symmetrical
Ovary Position
two terms describe
inferior ovary
result if receptacle tissue grows upward around the ovary
epigynous
superior ovary/hypogynous parts
more common arrangement
no fusion to ovary occurs
obviously above the flower parts
perigynous
intermediate
partially buried ovaries are half-inferior
Wind-Pollinated Flowers
totally distinct set of modifications is adaptive
pollination is aided by growth pattern of the plant population
species
grasses
oaks
hickories
all conifers
Inflorescences and Pollination
inflorescence
give collective visual signal tto pollinators
one small flower may be overlocked
but no hundred close together
two basic arrangements occur
determinate inflorescences
has only a limited potential for growth b/c the inflorescence apex is converted to a flower
end is possibilities for continued growth
indeterminate inflorescences
lowest or outermost flowers open first
new flowers still being initiated at the apex
Fruit Types and Seed Dispersal
True Fruits and Accessory Fruits
true fruit
"pericarp" and "fruit" have been applied to both types of fruit
used to refer to fruits contain only ovarian tissue
accessory fruit
false fruit
used if any from inferior ovaries
bulk of the fruit is enlarged base of sepals and petals
only the innermost part is true fruit derived from carpels
simple fruit
most common kind
fruit develop from a single ovary or the fused ovaries of one flower
aggregate fruit
separate carpels of one gynoecium fuse during development
rasperries
multiple fruit
fings
mulberries
pineapple
development all of the individual fruits of an inflorescence fuse into one fruit
Classification of Fruit TYpes
dry fleshy
emphasis is placed on the fruit
not typically eaten by the natural seed-distributing animals
fleshy fruits are eaten during the natural seed distribution process
dehiscent fruits
further classification of dry fruits emphasizes fruit opening
break open and release the seeds
such as
legume
follicle
caspule
schizocarp
indehiscent fruits
do not break open and release the seeds
such as
caryosis
achene
samara
nut
