Plant reproduction

What do haploid generation and diploid generation produce

Haploid generation produces gametes therefore gametophytes

Diploid generation produces spores snd therefore sporophyte

Heterogenesis

When two generations alternate to produce each other

Explain the alternations of generations

1. A single celled spore divides by mitosis and develops into a multicellular sporophyte

2. Haploid gametophyte produces haploid gametes (sperm and egg) by mitosis

3. A sperm fertilises an egg which results in a diploid zygote

4. The single celled zygote divides by mitosis and develops into a a multicellular sporophyte

5. The sporophyte produces haploid spores by meiosis

Explain the gymnosperm life cycle

1. Male DIPLOID microsporangium (2n) undergoes meiosis to form HAPLOID microspores n (pollen)

2. Female megasporangium has a spore mother cell that is DIPLOID

3. Pollination occurs when compatible microspore and megasporangium meet

4. Megasporangium undergoes meiosis to form megaspore n (ovule)

5. Male gametophyte forms tiny tube into female gametophyte for FERTILIZATION to occur 5 Zygote (2n)

6. Fertilized DIPLOID zygote is formed

7. Zygote develops into a seed

8. A seed germinates and forms a new sporophyte that is ready to grow

Flowers

Fowers are the site of pollination and fertilisation

Stigma

The landing platform for pollen

Style

A slender neck connecting stigma to ovary

Ovary

Houses one or more ovule and will eventually become a fruit

Anther

Produces pollen which houses cells that develop into sperm

Filament

A stalk to elevate the anther

Placenta

The part of the ovary where the ovules originate and remain attached until maturity

Receptacle

The thickened part of a stem from which the flower organs grow

Pedicel

A small, short stalk of leaf, fruit or sporangium

Nectary

A gland secreting nectar in flowers, and in some leaves

List the 5 major steps in the lifecycle of angisperms

1. Gametophyte development

2. Pollination

3. Fertilization

4. Seed development

5. Seed germination

Explain pollen development

Pollen grains are the male gametophytes

A Microspore Mother Cell (2n) in the anther undergoes meiosis First Undergoes meiosis I to produce 2 haploid spores (n) then Undergoes meiosis II to produce 4 haploid spores (tetrad) (n)

Each spore separates and Each separated spore then divides via mitosis

Diploid pollen grain has a Tube cell and a Generative cell

Mature pollen grain has a tough wall

• Pollen grains are released from the anthe

Explain the embryo sac development

An embryo sac is the female gametophyte

• A Megaspore Mother cell (2n) in the ovule undergoes meiosis and produces four haploid megaspores (n) •

Three of the spores degenerate

• The surviving spore undergoes a series of mitotic divisions (3 times) to produce the embryo sac

• One cell within the embryo sac is a haploid egg (n) ready to be fertilized • One central cell within the embryo sac has two nuclei and will produce endosperm

Pollination

Pollination is the transfer of pollen from anther (male gametophyte) to stigma (female gametophyre)

• Pollen may be carried by wind, water, and animals •

As a pollen grain germinates a Tube cell gives rise to the pollen tube, which grows downward into the ovary and a Generative cell divides by mitosis, producing two sperm cells

Fertilisation

When one sperm fertilizes the haploid egg to produce a diploid zygote and another sperm fuses with the diploid central cell nucleus and Produce a triploid (3n) cell that will give rise to the endosperm.

The endosperm nourishes the developing embryo • This formation of a diploid zygote and a triploid nucleus is called double fertilization

Explain how the ovule develops into a seed

1. The zygote first divides by mitosis to produce two cells

2. One cell becomes the embryo

. 3. The other cell divides to form a thread of cells that pushes the embryo into the endosperm

What does a mature seed have

1. An endosperm

2. One or two cotyledons

3. A root

4. A shoot

5. A tough seed coat Result from loss of water and Near end of maturation

Explain seed dormancy

Temporary suspension of growth and development

Monocot

1. A single cotyledon

2. An embryonic root and shoot with protective sheaths

3. Endosperm

Eudicot

1. Two cotyledons

2. Apical meristems that lack protective sheaths

3. No endosperm because the fleshy cotyledons absorbed the endosperm nutrients as the seed formed

How does the ovary develop into a fruit

Hormonal changes induced by fertilization trigger the ovary to develop into a fruit

Functions of fruits

House and protect seeds and aid in their dispersal

Explain monocot germination

1. A protective sheath surrounding the shoot pushes upwards and breaks through the soil

2. Shoot tip then grows up through the tunnel of the sheath

3. Cotyledon remains in the soil and decomposes

Eudicot germination

1. Embryonic root emerges first and grows downwards

2. Embryonic shoot emerges with the apical meristem “hooked” downward to protect it

3. As shoot breaks through soil, light triggers hook to straighten

4. Leaves expand from shoot tip and begin photosynthesis

5. The cotyledons emerge from the soil and become leaflike

How to identify monocots

Single cotyledon (seed leaf)

• Parallel leaf venation

• Scattered vascular bundles

• Flower parts in multiples of threes

•Shallow fibrous root system

Eudicots

Two cotyledons (seed leaves)

•Branched leaf venation

•A ring of vascular bundles

•Flower parts in multiples of fours or fives

•A taproot system

Fruits

Ripened ovaries of flowers and contain seeds

Name the Various adaptations that disperse seeds

1. Ballistic dispersal

2. Wind dispersal

3. Water dispersal

4. Animal attachment

5. Animal ingestion

Explain the reproduction in angiosperms in steps

1. MEIOSIS in the anthers produces HAPLOID spores that form the male gametophyte (pollen grains)

2. MEIOSIS in the ovule produces a HAPLOID SPORE that forms the few cells of the female gametophyte, one of which becomes the egg cell.

3. POLLINATION occurs when a pollen grain lands on the stigma. A pollen tube grows from the pollen grain to the ovule.

4. The tube carries a sperm that fertilises the egg to form a zygote.

5. Each ovule develops into a seed, consisting of an embryo (a new sporophyte) surrounded by a food supply snd a seed coat derived from the integuments.

6. While the seeds develop, the ovary’s wall thickens, forming the fruit that encloses the seeds.

7. When conditions are favorable, a seed germinates.

Seed germination

Seed germination is when a seed takes up water then The hydrated seed expands and ruptures its seed coat

Metabolic changes restart growth and development in the embryo