4.2 Sexual reproduction in plants

Question 1

What are 2 types of pollenation?

Answer 1

Wind
insect

Question 2

What are the male organs in an insect pollenated flower called? and what are their parts?

Answer 2

Stamen
Anther + fillament

Question 3

What are the female organs in an insect pollenated flower called? and what are their parts?

Answer 3

Carpel
ovary + style + stigma

Question 4

What are the four sets of modified leaves in insect pollenated flowers called?

Answer 4

Calyx
corolla
Androecium
Gynoecium

Question 5

What is the role of the gynoecium?

Answer 5

Female organs made up from carpels
closed structure where ovules develop

Question 6

What is the role of the androecium?

Answer 6

Male organs made up from stamens
site of pollen grain production (male gametes)

Question 7

What is the corolla?

Answer 7

The bright petals used to attract insects
forms the outer layer

Question 8

What is the calyx?

Answer 8

group of sepals
protect the flower

Question 9

What are the features of a wind pollenated flower?

Answer 9

Dull and scentless
no petals
feathery exposed stigma
pendulous organs

Question 10

What is dehiscence?

Answer 10

The splitting of the anther to release pollen grains

Question 11

How is the anther arranged?

Answer 11

four pollen sacs arranged in pairs
tapetum provided nutrience to mother cell
fibrous layers to protect the pollen
epidermis on outside

Question 12

How do pollen grains develop?

Answer 12

Mother cell splits by meiosis to form 4 haploid cells
Haploid cells split their nucleolus by mitosis to form a tube and generative nucleus

Question 13

What is the Tapetum?

Answer 13

A layer of cells that provide nutrients to developing pollen grains

Question 14

How does dehiscence ocour?

Answer 14

Anther dries out
Tension in lateral groves increases and splits the anther

Question 15

How does the ovule form?

Answer 15

1 cell from the nucellus enlarges and forms the megaspore mother cell
meiosis of the mother cell forms 4 haploid megaspores
3 degenerate and 1 develops into the embryo sac by mitosis (with 2 haploid nuclei)
divides 3 times by mitosis
8 nuclei form
2 polar nuclei remain central
Others develop cytoplasm and cell walls and half go to each pole of cell

Question 16

What is the structure of the ovule?

Answer 16

3 Antipodal cells at the top
2 synergies at base
1 female gamete at base

Question 17

How does pollen move in self fertlisation?

Answer 17

Transferred from anther to stigma of same plant

Question 18

How does pollen move in cross fertilisation?

Answer 18

Pollen from one plant is transferred to the
stigma of a different plant of the same
species

Question 19

How does variation occur in self pollination?

Answer 19

Mutation
crossing over in meiosis
independent assortment in meiosis

Question 20

How does variation occur in cross pollination?

Answer 20

Meiosis
mutation
combination of parental genomes

Question 21

What advantages do cross pollinators have over self pollinators?

Answer 21

More likely to survive changing environments due to more genetic variety

Question 22

How do plants prevent cross pollenation?

Answer 22

Chemical self- gamete incompatibility
Irregular flower structure

Question 23

What does dioecious mean?

Answer 23

Having separate male and female plants

Question 24

Why do plants cross pollenate?

Answer 24

Dioecious
separate m and f flowers
organs mature at different times
structural adaptations against self pollination

Question 25

Describe the process of double fertilisation

Answer 25

compatible pollen grain lands of stigma
stigma produces sugary solution germinating pollen grain
a pollen tube is produced
pollen tube grows down style secreting hydrolase to digest tissues style
generative nucleus splits by mitosis to 2 haploid gametes
P.T enters and tip bursts releasing gametes
1 fuses with egg –> Diploid zygote
1 fuses with polar nuclei –> triploid primary endosperm nucleus

Question 26

Where does the pollen tube enter the ovule?

Answer 26

The micropyle

Question 27

What does monoecious mean?

Answer 27

A plant with separate male and female flowers on the same plant

Question 28

What are the requirements for germination?

Answer 28

Suitable temperature
Water
Oxygen

Question 29

What happens to the ovule after fertilisation?

Answer 29

Becomes the seed

Question 30

What happens to the Diploid zygote after fertilisation?

Answer 30

Splits by mitosis to form a diploid embryo

Question 31

What happens to the triploid endosperm after fertilisation?

Answer 31

Mitosis to from endosperm tissue
a food store

Question 32

What happens to the Integuments after fertilisation?

Answer 32

Become testa

Question 33

What happens to the Micropyle after fertilisation?

Answer 33

Pore in testa

Question 34

What happens to the ovary after fertilisation?

Answer 34

Becomes fruit enclosing seeds

Question 35

What is an example of a non-endospermic fruit?

Answer 35

A broad bean

Question 36

What is the germination process of a non endospermic seed?

Answer 36

begins with water entering the micropyle
swells cotyledons splitting the Testa
more oxygen can enter for aerobic respiration
starch and proteins in cotyledons mobilised through hydrolysis
Used as energy source for respiration and growth of plumule and radicle

Question 37

What is an example of an endospermic seed?

Answer 37

Maize

Question 38

Describe the germination process for an endospermic seed

Answer 38

Water enters
Embryo releases gibberellin
Gibberellin diffuses to protine rich aleurone layer
amylase is made to breakdown starch stored in endosperm
glucose diffuses to embryo and used for aerobic respiration