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Chapter 26
Sexual
Reproduction
in Plants
The Bronx Botanical Garden
Pistil
Petal
Stamen
Seeds
Pollen
Tubes
(I) Structure of the Flower
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Some flowers contain
both stamen and pistil
while other flowers
contain only one of
the two
Petals and sepals are
also present in
flowers
(I) Structure of the Flower
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The complete circle of
petals is called a
corolla
The complete circle of
sepals is called a
calyx.
(A)
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Stamen
Male reproductive
structure
Composed of an anther
and filament
Through meiosis, the
diploid cells of the anther
produce pollen grains
that are haploid
(B)
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Pistil
Female reproductive
structure
Composed of stigma,
style, and ovary
As a result of meiosis,
the eggs developing
inside the ovary are
haploid
(III)
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Pollination
The transfer of pollen grains from the anther to
the stigma
Pollination may be aided by wind, insects, and
birds. In some instances, the colored petals act
as a visual attractant for insects
If pollination occurred in a dry environment, the
pollen grain would not dehydrate (dry up) due to
a thick wall that surrounds it
Two types of pollination:
1. Self-Pollination
2. Cross-Pollination
Self-Pollination
„
The transfer of pollen grains from
the anther to the stigma of the
same plant
Cross-Pollination
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The transfer of pollen grains from
the anther of a flower one one
plant to the stigma of a flower on a
different plant
„ Allows for variations due to the
combination of two different plants
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Following pollination,
the pollen grain
germinates to the stigma
and forms a pollen tube
Pollen tube is an
adaptation for internal
fertilization
Two haploid sperm cells
travel down the pollen
tube and only one
fertilizes the egg in the
ovule
(IV) Fertilization and Embryo Development
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The union of a sperm cell and an egg cell
results in the formation of a zygote
The zygote undergoes development
resulting in the formation of an embryo
(ripened ovule)
The ripened ovule develops into the seed
The ripened ovary develops into the fruit
Plant Embryo (seed)
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Hypocotyl- develops into
the root, and in some
species, the lower portion
of the stem
Epicotyl- develops into
leaves and the upper
portion of the stem
Cotyledon- contains
stored food and provides
nutrients for the
germinating plant
(V)
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Germination
In flowering plants, seeds develop within fruits
which are specialized structures that aid in seed
dispersal
Ex: animal eats fruit Æ feces
Germination will occur if there is:
1. Sufficient moisture
2. Proper temperatures
3. Oxygen
(VI)
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Growth
Growth occurs in specific regions known as
the meristematic region
Two types:
1. Apical meristem- region of growth found
in the tips of stems and roots (length of
plant)
2. Cambium- region of growth located
between the xylem and phloem (width of
plant)