Unit 2- Sexual Reproduction In Plants

Question 1

What is a microspore and where is it produced?

Answer 1

Plant male gamete

Anthers

Question 2

What is a mega spore?

Answer 2

Plant female gamete

Ovule

Question 3

What is microsporogenesis?

Answer 3

The production of microspores

Question 4

Describe the process of micro genesis:

Answer 4

Diploid microsporophytes/pollen mother cells in the anther divide by meiosis into 4 haploid microspores
Microspores— develop tough thick wall, nucleus divides to form 2 haploid nuclei (generative nucleus and pollen tube nucleus)—> pollen

Question 5

What happens to pollen when it lands on a female stigma?

Answer 5

The generative nucleus divides again by mitosis

Question 6

What is the process of producing megaspores called?

Answer 6

Megasporogenesis

Question 7

What is the final product of megasporogenesis?

Answer 7

A mature gametophyte
3 antipodal cells at top
2 polar nuclei in the centre
2 synergid cells at bottom left and right
A female gamete bottom centre

Question 8

Describe megasporogenesis

Answer 8

A large megaspore mother cell — meiosis—> 4 haploid megaspores, but the division is uneven = 1 megaspore with all the cytoplasm of the mother cell and 3 small megaspores that disintegrate
Large megaspore grows, nucleus divides 3 times by mitosis, to form 8 haploid nuclei
Membranes form splitting the megaspore into 7 cells (embryo sac), 1 female gamete, 2 polar nuclei cell and 5 other

Question 9

What is cross pollination?

Answer 9

When pollen of a plant lands on the stigma of another plant of the same species

Question 10

How does the pollen tube form?

Answer 10

The pollen tube nucleus in the pollen grain, secretes digestive enzymes that breaks down the style tissue and uses the digested products for growth

Question 11

Why is plant sexual reproduction known as double fertilisation?

Answer 11

The 2 male gamete nuclei both fuse with part of the embryo sac

• one male gamete nucleus fuses with the female gamete to form diploid zygote
• one male gamete nucleus fuses with the 2 polar nuclei cell to form a triploid primary endosperm cell

Question 12

Summary of plant fertilisation:

Answer 12

• pollen grains are released by anther, disperse in the wind and land on a stigma
• pollen grain germinate by absorbing water on stigma and splitting
• the generative nucleus divides by mitosis into 2 haploid nuclei
• pollen tube emerges from the split, secreting enzymes breaking down the style and using the digested tissue to grow
• pollen tube nucleus is at top of pollen tube while the 2 haploid nuclei follow behind
• pollen tube gets to the embryo sac through a small hole (micropyle) pollen tube nucleus degenerates
• double fertilisation occurs, producing tiploid primary endosperm cell and a diploid zygote

Question 13

What are the 2 products of plant double fertilisation?

Answer 13

Diploid zygote, male haploid nucleus fused with female haploid gamete
Primary endosperm, male haploid nucleus fused with 2 polar nuclei cell

Question 14

What happens at germination?

Answer 14

The pollen grain absorbs water to germinate and splits open

The pollen tube breaks out beginning to digest the style tissue forming a pollen tube

Question 15

What happens to the zygote?

Answer 15

It develops into the embryo

Question 16

What is the purpose of the primary endosperm?

Answer 16

To develop into a food store to nourish the embryo like coconut flesh