4.2 Plant reproduction

Question 1

What is the male gamete (plant)?

Answer 1

Pollen grain

Question 2

What is the female gamete (plant)?

Answer 2

Ovum

Question 3

What is pollenation?

Answer 3

The transfer of pollen from the anther of one flower to the stigma of the other

Question 4

What are the traits of a wind-pollinated flower?

Answer 4

-Feathery stigma
-Anther and stigma hang out of plant
-No petals/green petals
-No scent/nectar
-Large volume of small, smooth, light pollen grains

Question 5

What are the traits of an insect-pollinated flower?

Answer 5

-Colourful petals with nectar guides
-Scented and nectar (sucrose)
-Anther and stigma in plant
-Small amount of large, sculpted, sticky pollen

Question 6

What part of the anther provides nutrients to male gametes?

Answer 6

Tapetum

Question 7

How many times do pollen mother cells undergo meiosis?

Answer 7

twice

Question 8

What are the characteristics of the pollen cell wall?

Answer 8

-Blocks UV light to prevent mutation
-Tough and resistant to desiccation
-Sculpted/smooth

Question 9

What are the nuclei found in a pollen grain, and what is their function?

Answer 9

-pollen tube nucleus: guides pollen tube to micropyle
-Generative nucleus x2: fertilises ovum/polar bodies

Question 10

What is dehiscence?

Answer 10

The opening of an anther, releasing pollen grains via stomium

Question 11

What are the integuments in the ovary?

Answer 11

2 walls of the ovule

Question 12

What provides nutrition for the megaspore?

Answer 12

Nucellus

Question 13

How many times does a mother megaspore cell undergo meiosis?

Answer 13

1

Question 14

How many times does a megaspore undergo mitosis?

Answer 14

3

Question 15

What are the different nuclei called in an embryo sac?

Answer 15

• 2x polar nuclei
  -3x antipodals
  -2x synergids
  -1x ovum

Question 16

What is the function of the fertilised polar bodies?

Answer 16

They become triploid endosperm, used for nutrition of the ovum

Question 17

What is the function of the synergids?

Answer 17

To guide pollen tube to ovum

Question 18

What is the function of the antipodals?

Answer 18

Nothing, they disintegrate

Question 19

What are the advantages of self-pollination?

Answer 19

-Reliable
-Successful in harsh environments where pollinators are scarce
-Good for preserving successful genotypes in stable environment

Question 20

What are the disadvantages of self-pollination?

Answer 20

-Inbreeding reduces genetic variation
-Relies upon crossing over, mutations, and random assortment for genetic variation
-Greater chance of homozygous recessive individuals

Question 21

What are the advantages of cross-pollination?

Answer 21

-Maintain genetic variation
-Reduced chance of homozygous recessive individuals

Question 22

What are the disadvantages of cross-pollination?

Answer 22

-Relies on the successful transfer of pollen

Question 23

What are the 4 cross-pollination mechanisms?

Answer 23

-Monoecious/Dioecious
-Protandry/Protogyny
-Self-incompatIbility
-Structural-incompatibility

Question 24

What does Monoecious mean?

Answer 24

Separate male and female flowers on the same plant

Question 25

What does dioecious mean?

Answer 25

Separate male and female plants

Question 26

What is genetic self-incompatibility?

Answer 26

Pollen cannot germinate on the stigma of the same flower

Question 27

What is structural incompatibility?

Answer 27

Anther is below stigma so pollen cannot drop onto the stigma

Question 28

How does fertilisation occur?

Answer 28

1) Pollen grain lands on stigma, germinates in sucrose solution secreted by stigma, and produces pollen tube
2) Pollen tube grows down into style and generative nucleus undergoes mitosis
3) Pollen tube enters embryo sac via micropyle

Question 29

What part of the seed do the polar bodies become?

Answer 29

Endosperm

Question 30

What part of the seed does the ovule become?

Answer 30

The seed

Question 31

What part of the seed does the ovary become?

Answer 31

The fruit

Question 32

What part of the seed do the integuments become?

Answer 32

Testa

Question 33

What happens when a seed is monocotyledon?

Answer 33

-Endosperm remains
-Testa fuses with ovary wall

Question 34

What happens when the seed is a dicotyledon?

Answer 34

-Plumule will become shoot
-Radicle will become root
-Endosperm absorbed into cotyledon
-Non-Endospermic

Question 35

What are the seed dispersal mechanisms?

Answer 35

-Wind
-Animals
-Water
-Rolling
-Bursting

Question 36

What is dormancy?

Answer 36

When a seed’s growth is suspended?

Question 37

What can break dormancy?

Answer 37

-Heat
-Cold
-Scarification
-Soaking

Question 38

What are the benefits of dormancy?

Answer 38

-Low metaboli rate (survive cold weather)
-Testa is chemcially resistant
-Endosperm/Cotyledon provides nourishment
-Dispersal away from parent reduces competition
-Inhibitors prevent germination

Question 39

What are the conditions for germination?

Answer 39

-Water to soften testa
-Oxygen for aerobic respiration
-Suitable temperature for enzymes

Question 40

How does germination occur in Non-Endospermic seeds?

Answer 40

1) Water absorbed through micropyle
2)Testa ruptures and radicle pushes downward
3)Amylase hydrolyses Starch into Maltose, which goes to plumule and radicle
4)Plumule bends over into a hook to protect tip against soil abrasion, unfurls once above soil and starts photosynthesizing

Question 41

How does germination occur in Endospermic seeds?

Answer 41

1) Water absorbed by seed
2) Gibberellic acid synthesised by embryo, initiating germination
3) GA diffuses into Aleurone layer surrounding endosperm & stimulates Amylase synthesis
4) Amylase hydrolyses Starch into Maltose
5) Maltose converted to glucose for respiration
6) Glucose transported to embryo, providing energy for growth