REPRODUCTION IN PLANTS

Question 1

Define asexual reproduction.

Answer 1

Process whereby one parent produces genetically identical offspring.

Question 2

Define sexual reproduction.

Answer 2

Process whereby two gametes fuse together to form an entirely new organism that is genetically different from its parents.

Question 3

What is the reproductive organ of flowering plants?

Answer 3

Flower

Question 4

What are the main parts of the flower?

Answer 4

1. Petal
2. Stamen
3. Receptacle
4. Sepal
5. Nectary
6. Carpel/Pistil
7. Pedicel

Question 5

Describe the petal in animal-pollinated and wing-pollinated plants.

Answer 5

AP
- brightly-coloured, sometimes scented to attract animals to bring about pollination

WP
- dull, unscented

Question 6

What are the parts of the stamen?

Answer 6

Anther and filament

Question 7

Describe the filament and its function.

Answer 7

Long stem-like structure that positions the anther so that pollen grains can be pollinated by agents.

Question 8

Describe the anther and its function.

Answer 8

Made up of two or four pollen lobes, each containing two pollen sacs where pollen grains are formed

Question 9

Describe the receptacle and its function.

Answer 9

Expanded end of the pedicel that holds the flower

Question 10

Describe the sepal and its function.

Answer 10

Modified leaves that are green in colour. They protect the flower when it is in the bud shape.

Question 11

Describe the nectary and its function.

Answer 11

Found in insect-pollinated flowers only and produces sugary nectar to attract insects/birds.

Question 12

What are the parts of the carpel/pistil?

Answer 12

Style, stigma, ovary

Question 13

Describe the stigma and its function.

Answer 13

Sticky (AP) or feather-like (WP) surface for pollen grains to attach to.

It secretes a sugary fluid that stimulates the germination of pollen grains after pollination.

Question 14

Describe the style and its function.

Answer 14

Connects the stigma to the ovary, and holds it in position to trap pollen grains. Made up of soft tissues that allow the pollen tube to grow down.

Question 15

Describe the ovary and its function.

Answer 15

Contains and protects the ovules

Question 16

Describe the ovule.

Answer 16

Contains female gametes

Question 17

Define pollination.

Answer 17

Transfer of pollen grains from the anther to the stigma

Question 18

What is the difference between cross and self-pollination?

Answer 18

In cross-pollination, pollen grains are transferred to the stigma of a flower on another plant of the same kind. In self pollination, pollen grains are transferred to the stigma of the same or different flower of the same plant.

Question 19

What factors promote self-pollination?

Answer 19

1. Bisexual flowers with anthers and stigma maturing at the same time
2. Stigma located directly below the anthers

Question 20

What factors promote cross-pollination?

Answer 20

1. Plants bearing only male or female flowers (dioecious plants)
2. Anthers and stigmas of bisexual flowers maturing at different times
3. Biochemical block when pollen of a flower lands on the stigma of a flower on the same plant, preventing flower from germinating

Question 21

What are the advantages of self-pollination?

Answer 21

1. Not dependent on external pollinators (e.g. insects, wind)
2. Less wastage of pollen and energy
3. Only one parent plant is required

Question 22

What are the disadvantages of self-pollination?

Answer 22

1. Produces offspring genetically identical to the parent -> loss of genetic diversity + less adapted to environmental changes

Question 23

What are the advantages of cross-pollination?

Answer 23

1. Greater genetic variation -> higher chance of surviving environmental changes
2. Offspring can inherit favourable traits from both parents

Question 24

What are the disadvantages of cross-pollination?

Answer 24

1. Relies on pollinators -> energy consuming, and wastage of pollen grains
2. Two parent plants required

Question 25

What are the differences between insect-pollinated and wind-pollinated flowers in terms of petals, scent, nectary guide and pollen?

Answer 25

PETALS
AP: Large, brightly-coloured
WP: Small, dull (flower parts protected by bracts)

SCENT
AP: Scented
WP: Unscented

NECTARY GUIDE
AP: Present
WP: Absent

POLLEN
AP: Smaller quantities; large, sticky and heavy pollen with rough surface
WP: Large quantities; small, dry and light pollen with smooth surface

Question 26

What are the differences between insect-pollinated and wind-pollinated flowers in terms of reproductive parts?

Answer 26

STAMEN
AP: Small, firmly attached to filament inside the flower
WP: Large, loosely attached to filament and hanging out of the flower

STIGMA
AP: Small and sticky, inside the flower
WP: Large and feathery, protrudes out of the flower

Question 27

Describe fertilisation in plants (after a pollen grain from an anther lands on a stigma).

Answer 27

1. Pollen grain absorbs sugary liquid from the stigma and germinates
2. Pollen tube cell grows into a pollen tube, growing through the cells of the style by secreting enzymes to digest them
3. Pollen tube enters the ovary and then the ovule through the micropyle in the ovule
4. Generative nucleus divides to form two male gametes
5. The male gametes travel down the pollen tube into the ovule
6. One of the male gametes fuse with the ovum to form the zygote
7. The zygote undergoes cell division to develop into the embryo
8. The ovule will develop into a seed and the ovary will develop into a fruit