Ch. 24Reproduction
of Seed Plants
 I.
Reproduction With Cones
and Flowers

A. Alternation of Generations
Haploid
Diploid
All plants have a life cycle in
which a diploid sporophyte
generation alternates with a
haploid gametophyte
Sporophyte Plant
generation.
MEIOSIS
-
Gametophyte Plant (N)
(2N)
FERTILIZATION
 B.
Life Cycle of Gymnosperms
 - Reproduction in gymnosperms
takes place in cones, which are
produced by a mature
sporophyte plant.
 1.
Pollen cones
a. Also called male cones.
b. Produces the male
gametophytes, which are
called pollen grains.
 2.
Seed Cones
 a. Produce female gametophytes
 b. Much larger than pollen cones
 c. At the base of each cone scale
are found
2 ovules in which the female
gametophytes
develop
 3.
Pollination – The pollen is carried by
the wind and caught on a sticky
secretion (pollination drop) on one of
the scales of the female cone.
 4.
Fertilization
a. When a pollen grain lands near
an ovule, it grows a pollen tube
into the ovule.
b.
A sperm from the pollen tube
fertilizes the egg in the ovule.
Development
a. Fertilization produces a
zygote
which grows into an
embryo
b. The embryo becomes
enclosed in a seed
5.
ANGIOSPERM
 C.
Structure of Flowers
 - Flowers are the reproductive
organs that are composed of four
kinds of specialized leaves: sepals,
petals, stamens, and carpels.
(Figure 24-5)
Pistil
Stamen
Filament Anther
Style Stigma
Ovary
Petal
Ovule
Sepal
 1.
Sepals
a. The outermost
circle of floral parts
contains the sepals,
which in many plants
are green and
closely resemble
ordinary leaves
b.
Enclose bud and
protect the flower
during development
 2.
Petals
a. Brightly colored and found just
inside the sepals
b. Attract insects and other
pollinators to the flower
 3.
Stamens
a. Produce male
gametophytes –
pollen grains
b.
Consists of anther
and filament
 4.
Carpels
a. Also called pistils
b. produce female
gametophytes – eggs
c. Consists of ovary, style, and
stigma
 D.
Life Cycle of Angiosperms
 1. Reproduction in angiosperms
takes place within the flower
 2. Following pollination and
fertilization, the seeds develop
inside protective structures
 E.
Pollination
 1. Most gymnosperms and some
angiosperms are wind pollinated,
whereas most angiosperms are
pollinated by animals.
 2. Insect pollination is more
efficient than wind pollination,
giving insect-pollinated plants a
greater chance of reproductive
success.
 F.
Fertilization in Angiosperms
1. Double Fertilization – Inside the
embryo sac, two distinct fertilizations
take place
a. First, one of the sperm nuclei
fuses with the egg nucleus to
produce a diploid zygote, which will
grow into the new plant embryo.
 b.
Second, the other sperm nucleus
fuses with two polar nuclei in the
embryo sac to form a triploid (3N)
cell. This will grow into a food-rich
tissue know as endosperm, which
nourishes the seedling as it grows.
 II.
Seed Development and
Germination
 - the development of the seed,
which provides protection and
nutrition for the embryo, was a
major factor in the success of
plants on land.
 A.
Seed and Fruit Development
1. As angiosperm seeds mature,
the ovary walls thicken to form a
fruit that encloses the
developing seed.
2.
The term fruit, biologically
speaking, applies to any seed
that is enclosed within its embryo
wall.
 http://www.youtube.com/watch?v=zVNs
CW6eiiw
 B.
Seed Dispersal
1. Dispersal by Animals- Seeds
dispersed by animals are
typically contained in fleshy,
nutritious fruits.
 2.
Dispersal by Wind and WaterSeeds dispersed by wind or water
are typically light weight, allowing
them to be carried in the air or to
float to the surface of the water.
 C.
Seed Dormancy
1. Some seeds sprout rapidly
while other seeds enter a period
of dormancy, during which the
embryo is alive but not growing.
2.
Environmental factors such as
temperature and moisture can
cause a seed to end dormancy
and germinate.
 D.
Seed Germination
- The early growth stage of the
plant embryo