science world

Flowering plants have sporophyte and gametophyte stages. The sporophyte is diploid and consists of roots, stems, and leaves. The sporophyte produces flowers for sexual reproduction. Flowers produce haploid spores that develop into gametophytes. The female gametophyte is embeddcd in floral tissues. The male is released as pollen grains.

Accessory structures form the non reproductive parts of the flower.

A flower has a ring of leaf like sections round the base.

These are called SEPALS.
Inside the SEPALS are the PETALS.
The PETALS can be a variety of shapes and colours.
The PETALS form the COROLLA.
The SEPALS form the CALYX

Reproductive parts include the stamens (male) and carpels (female).

1) THE STAMEN
Inside the COROLLA are slender stalks.
These are called FILAMENTS.
At the end of the FILAMENT is the ANTHER.
The ANTHER and the FILAMENT together form the STAMEN.
The STAMEN is the MALE reproductive ORGAN.
Pollen grains are found on the ANTHER.
2) CARPEL
At the centre of the COROLLA is the CARPEL.
This is the FEMALE reproductive ORGAN. It is made up of the:
1)STIGMA

2)STYLE

3)OVARY.
The pollen from the male part, the STAMEN, is needed to fertilise the female part, the CARPEL.
The female reproductive organ is the CARPEL
The male reproductive organ is the STAMEN

Pollen is basically sperm packed inside a nutritious package. When it first

evolved it was transferred by wind currents. Later it was transferred by insects. Most species of angiosperms have coevolved with pollinators attracted to their pollen and nectar. Coevolution refers to two (or more) species jointly evolving as an outcome of close ecological interactions. Plants with flowers that attracted insect pollinators had a reproductive advantage. Plant structures that were more attractive to pollen-delivering insects were favored. The more attractive plants proved to be good sources of food for the insects.
In the ovary, eggs develop, fertilization occurs, and seeds mature.

SO LET'S HAVE A LOOK AT WHAT MAKES UP THE OVARY
The OVARY contains one or more OVULES.
The OVULES are the parts that develop into seeds. They contain female egg cells.

Double fertilization is a distinctive feature of angiosperms. The male gametocyte delivers two

sperm to an ovule. One sperm fertilizes the egg and the other fertilizes a cell that gives rise to endosperm that supports the embryo.Pollination is the transfer of pollen grains to the surface of a receptive stigma. Wind, insects, birds, or other agents are often required for the transfer. After a pollen grain lands on a stigma, it germinates and a pollen tube forms, creating a path that the two sperm nuclei will follow to the ovule.
Guided by chemical cues, the pollen tube grows through the tissues of the ovary to an ovule. It carries two sperm nuclei. When the pollen tube reaches an ovule, it penetrates the embryo sac and deposits two sperm. The two sperm are released to accomplish double fertilization.
One sperm fuses with (fertilizes) the egg nucleus to form a diploid zygote. The other sperm nucleus fuses with the two endosperm nuclei to yield a triploid "primary endosperm cell," (endosperm mother cell) that will nourish the young sporophyte seedling.
Endosperm formation occurs only in angiosperms. The fusion of a sperm nucleus with the two nuclei of the endosperm mother cell produces a triploid (3n) cell. This cell will give rise to the endosperm, the nutritive tissue of the seed.