Flowering Plants:
Reproduction and Development
The process of meiosis and
fertilization occur in the flower, a
plant structure specialized for
sexual reproduction.
Flower Structure:
• The flower may contain both the male
reproductive organ, the stamen, and
female reproductive organ, the pistil.
• Flowers with both reproductive organs are
called perfect or complete flowers, while
those with only one or the other are called
imperfect or incomplete flowers. Petals
and sepals may also be present.
• The stamen is composed
of an anther and a
filament. As a result of
meiosis, the diploid cells
of the anther produce
pollen grains which
contain monoploid nuclei
(n).
• The pistil is composed of
the stigma, style, and the
ovary. As a result of
meiosis, ovule(s),
developing within the
ovary, contain the
monoploid egg nucleus
(n).
Pollination
• Pollination is the transfer of
pollen grains from the anther to
the stigma. Pollination may be
accomplished by wind, insects,
and birds. In some instances,
the colored petals act as a
visual attractant for insects
while nectar acts as a
chemical attractant.
• After pollination, the pollen
grain forms a pollen tube
which extends to the ovule and
moves the sperm nuclei to the
ovule.
Two Types of Pollination
• Self-pollination – the transfer of pollen from
anther to stigma of the same flower or to stigma
of another flower on same plant.
• Cross-pollination – transfer of pollen from an
anther on one flower to a stigma of a flower on a
different plant.
* Enhances variation (increases variety). The
pollen grain may be thick in dry climates to
prevent dehydration.
Fertilization and Embryo
Development
• The union (fusion) of
male and female nuclei in
the ovule results in a
zygote. The zygote
undergoes development
resulting in the formation
of the embryo. The
ripened ovule, containing
the embryo develops into
the seed.
• A seed consists of a
seed coat, which
develops from the
outer covering of the
ovule, and an
embryo. The ripened
ovary develops into
the fruit.
Three Parts of a Plant Embryo
1. Hypocotyl – develops
into root and lower stem
portion
2. Epicotyl – develops into
leaves and upper
portions of stem.
3. Cotyledon – contains
stored food which
provides nutrients for
germinating plant.
A – hypocotyl
B – epicotyl
C – seed coat
D - cotyledon
Germination
• In flowering plants, seeds develop inside a fruit.
Fruits are specialized structures which aid in
seed dispersal. Under suitable environmental
conditions, the dispersed seeds germinate. For
most seeds these conditions include:
 Sufficient moisture
 Proper temperature
 Sufficient oxygen
• The development of a seed into a mature plant,
which is capable of reproduction, involves cell
division, differentiation, and growth.
• Growth in higher plants is
restricted largely to
specific regions known as
meristems.
• Apical meristems are
found in the tips of roots
and stems and are
responsible for the growth
in the length of the plant..
• Some plants also contain
an active lateral meristem
region, the cambium,
located between the
xylem and phloem. This
is responsible for the
growth in diameter of
roots and stems.