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Angiosperms
-Are the most evolved and successful plants
-Their life cycle has three unique features, all of
which start with the letter f, fruits, flower, and
double fertilization
Flower Structure and Function
-Flowers function in sexual reproduction
-The four flower organs are sepals (asex), petals
(asex), stamen (male), and carpel (femalepistals)
-Stamens consist of two parts: Anther, which
produces pollen and filament which holds it up
-Carpels consist of three parts:
--Ovaries: produces ovules (will become seeds)
--Stigma: catches pollen grains
--Style: Narrow tube connecting the stigma to
the ovary
-Pollen develops within the microsporangin of
anthers
-Ovules develop from megapores within the
ovary
Gamete Formation
Pollination
-Is the transfer of pollen from an anther ro a
stigma
-If pollination is successful, a pollen grain
produces a pollen tube, which grows down into
the ovary
-The pollen tube is significant because it protects
and delivers the sperm to the ovule, allowing
angiosperms to reproduce outside of water
Double Fertilization
The Seed
-When the pollen tube reaches the ovule, two
fertilization events occur:
-One sperm fertilizes the egg, forming the
zygote, the zygote will develop into the embryo
and eventually the new sporophyte plant
-The other sperm combines with both polar
nuclei, forming a triploid (3n) nucleus, this
unique 3n tissue will give rise to the endosperm,
a food-storing tissue in the seed
-The union of two sperm cells forming both
zygote and endosperm is unique to angiosperms
-After double fertilization, the ovule develops
into a seed and the ovary develops into the fruit,
which encloses the seed
-The seed coat protects the embryo and its food
supply
-A radicle is the embryonic root
-The epicotyl consists of the shoot tip with a pair
of miniature leaves
Cotyledons
-The food reserves of the endosperm are
exported to structures termed cotyledons
(monocotyledons have one and dicotyledons
have 2)
-Monocot: corn
-Dicot: bean
Seed Germination
-As the seed matures, it enters dormancy, in
which it has a low metabolic rate and its growth
and development are suspended. The seed
resumes growth when there are suitable
environmental conditions for germination
Steps to Seed Germation
1.Imbibes water
2.Breakdown food reserve (endosperm)
3.Start root cell division
4.Root spouts
5.Stem sprouts
6.Foliage leaves sprout
Fruit form and Function
-The fruit protects the enclosed seeds and aids in
wind dispersal or in the attraction of seeddispersing animals
Flowering Plants Reproduce
-Sexual
-Asexual
-Both
Asexual Reproduction
-Models of asexual reproduction include
fragmentation where detached vegetative
fragments of some plant shoots can develop into
whole offspring
-The root system also give rise to many shoots
that can become a separate shoot system,
resuting in clones of the original plant
-Agriculture uses several techniques of artificial
vegetative reproduction such as grafting,
growing clones from cuttings, and test tube
clones to produce thousands of good variety
clones
Advantages of Asexual Reproduction
-No need for a pollinator
-Allows the plant to pass on all of its traits
-Since clones usually arise from mature
vegetative fragments of the plant, they receive
genes that allow it to be well adapted to the
same environment that allowed the parent plant
to flourish
Disadvantage of Asexual Reproduction
-The genetic uniformity of a clone puts them at
risk for extinction if there is a sudden change in
the environment
Advantage for Sexual Reproduction
-Generates variation, allowing adaptations to
change in the environment
-Seed dormancy allows growth to be postponed
until conditions are favorable
-Seeds allow dispersal of offspring to more
distant locations
Disadvantages for Sexual Reproduction
-Seedlings are usually fragile, making the
production of enormous amounts of seeds
necessary, using a large amount of the plant’s
resources