Chapter 6.1 - Structure of a Flower, Chapter 6.2 - Development of Pollen Grains and Embryo Sac

Integument

Two layers that is developed from the nucellus tissue.

Function of placenta

Supplies nutrients to the ovule through the funicle.

Placenta

The area of attachment of the funicle to the ovary.

Stamen

Male reproductive organ of a flower.

Nucellus

A lump formed from the development of mass of tissues inside the ovary. Consists of parenchyma tissue.

Funicle

A stalk that attaches the ovule to the ovary wall.

Function of micropyle

Allows the entry of water and air into the seed during germination.

Micropyle

An opening in the end of integuments of an ovule.

Stamen consists of

Anther and filament.

Similiarities between male and female parts of a flower

Both produce gametes and both are located at the flower's organ.

Development of pollen grains (1)

During the development of anther, a group of tissues grows inside each lobe to form four pollen sacs. In each pollen sac, there are hundreds of pollen mother cells, called microspore mother cells which are diploid (2n).

Carpel

Female reproductive organ of a flower.

Anther

Part of stamen that produces pollen grains.

Besides the male and female reproductive organs, what other structures do flowers have?

Peduncles, sepals and petals.

Carpel consists of

Stigma, style and ovary.

Ovules

Structures of a flower formed inside the carpel.

Development of the embryo sac (1)

The megaspore mother cell (2n) divides by meiosis to produce four haploid (n) megaspore cells.

DEvelopment of pollen grains (2)

The microspore mother cell divides by meiosis to produce four haploid (n) microspore cells. These four microspore cells are collectively known as tetrad. Each cell in the tetrad develops into a pollen grain.

Development of pollen grains (3)

The nucleus in the pollen grain divides by mitosis and produces two nuclei, namely the generative nucleus and tube nucleus. The wall of the pollen sac, which is thick and waterproof, breaks when the pollen grain matures. The pollen grains are released.

Development of the embryo sac (3)

The nucleus of the cell that has developed, divides mitotically three times to produce a cell with eight nuclei.

Development of the embryo sac (2)

Three of the megaspore cells degenerate and only one megaspore cell develops.

Development of the embryo sac (4)

Three nuclei move to one end of the embryo sac to form three antipodal cells. Another three nuclei move to the opposite end of the embryo sac and form two synergid cells and one egg cell. Two nuclei in the centre of the embryo sac form the polar nuclei.

Do flowers have male and female reproductive organs?

Yes.

Ovules develop from

a layer of tissues inside the ovary.

Megaspore mother cell/embryo sac mother cell develops to form

an embryo sac.

Male flower part produces _______ whereas female flower part produces ___________.

pollen grains, embryo sac.

Male flower part is __________ whereas female flower part is located at __________.

projected out from base of ovary, middle part of flower.