Topic 2 - Gametogenesis + Fertilisation in Plants

Question 1

describe pollen formation

Answer 1

• diploid microspore mother cell in anthers undergo meiosi -> for 4 haploid microspores
• haploid microspores under go mitosis tomature into pollen grains
• pollen grains consist of 2 nuclei -> generative nucleus and the pollen tube nucleus and protective coating

Question 2

Describe ovum formation in plants

Answer 2

• diploid megaspore mother cell in ovule undergoes meiosis -> forming an ootid and 3 polar bodies which degenerate and are reabsorbed
• ootid undergoes 3 mitotic divisions to form an embryo sac.
  **Embryo sac contains ** -> 2 polar bodies (form endosperm)
  -> an egg cell (forms zygote)
  -> 2 synergids (help the generative nucleus reach egg cell)
  -> 3 antipodal cells (no established function)
  with protective coating

Question 3

random knowledge

what are synergids

Answer 3

Synergid cells are 2 specialized cells which are located into embryo sac of female gametophyte, beside egg cells. Functions: It nourishes the ovum and give direction in the pollen tube

Question 4

Describe fertilisation in plants

Answer 4

• pollen grain (composed of pollen tube nucleus and the generative nucleus) adheres to the stigma, subsequently germinates
• pollen tube grows down stlye via secreation of digestive enzymes (digest surrounding tissue + uses it as source of nutrition).
• pollen tube grows through microphle into embryo sac
• Generative nucleus of pollen divides by mitosis to produce 2 sperm cells - enter embryo sac
• Double fertilisation occurs: 1 male gamete fuses with female nucelus - form diploid zygote
• other male gamete fuses with 2 polar nuclei, form tripoid endosperm nuclei -> source of nutrients for embryo

subsequently - following

Question 5

What is pollination?

Answer 5

The transfer of pollen grains from the anther to the stigma.

Question 6

What are the two types of pollination?

Answer 6

Self-pollination (same plant) and cross-pollination (different plants of the same species).

Question 7

What happens to a pollen grain when it lands on a compatible stigma?

Answer 7

It absorbs water and germinates, forming a pollen tube that grows down the style toward the ovary.

Question 8

What controls the growth of the pollen tube?

Answer 8

The tube nucleus.

Question 9

How many male nuclei travel down the pollen tube?

Answer 9

Two male nuclei.

Question 10

Where is the embryo sac located?

Answer 10

Inside the ovule, which is within the ovary.

Question 11

What does the embryo sac contain?

Answer 11

One egg cell, two polar nuclei, and other supporting cells.

Question 12

What is double fertilisation?

Answer 12

When one male nucleus fuses with the egg cell to form a diploid zygote, and the other fuses with the two polar nuclei to form a triploid endosperm.

Question 13

What is the result of the first fertilisation in flowering plants?

Answer 13

A diploid zygote that develops into the embryo.

Question 14

What is the result of the second fertilisation in flowering plants?

Answer 14

A triploid endosperm that nourishes the developing embryo.

Question 15

What does the zygote develop into?

Answer 15

An embryo (young plant).

Question 16

What does the ovule become after fertilisation?

Answer 16

A seed.

Question 17

What does the ovary become after fertilisation?

Answer 17

A fruit.

Question 18

Define fertilisation in plants.

Answer 18

The fusion of a male and female gamete to form a zygote.

Question 19

Define double fertilisation.

Answer 19

One sperm nucleus fertilises the egg; the other fertilises the polar nuclei to form endosperm.

Question 20

What is the function of endosperm?

Answer 20

To act as a nutritive tissue that nourishes the developing embryo.

Question 21

What term describes the fusion of gametes in flowering plants?

Answer 21

Fertilisation.

Question 22

Why is double fertilisation important?

Answer 22

It ensures the formation of both the embryo and its food supply (endosperm).