R2101 3.1 Describe the structure and state the functions of flowers

Question 1

Main functions of flowers (3)

Answer 1

1. Aid pollination (attracting pollinators of by wind)
2. Give rises to seeds and fruits
3. Flower type and shape can be used for classification e.g. Monocots have flowers arranged in threes or multiples of threes. Dicots have their flower parts arranged in fours or fives, or multiples of these

Question 2

2 types of reproduction in flowers

Answer 2

1. Sexual reproduction - formation of new individuals through the fusion of male and female sex cells (gametes). Results in variable off spring
2. Asexual reproduction - formation of new individuals without the fusion on gametes resulting in genetically identical offspring

Question 3

Parts of a dicot flower (13)

Answer 3

1. Receptacle
2. Sepal
3. Petal
4. Calyx (all sepals)
5. Corolla (all petals)
6. Nectary
7. Anther
8. Filament
9. Stamen
10. Stigma
11. Style
12. Ovule
13. Ovary

Question 4

Part of a monocot flower (7)

Answer 4

1. Tepal
2. Anther
3. Stigma
4. Filament
5. Style
6. Ovary and Ovule (not visable)
7. Receptacle

Question 5

What is the pedicel?

Answer 5

This is a flower stalk. The stalk of the flower head is the peduncle.

Question 6

What is a bract?

Answer 6

1. A leaf like structure at the base of a flower.
2. These can sometimes assume the function of attracting pollinators.
3. Can sometimes be larger than the flower itself.
4. Many flowers dont have bracts

Question 7

What is the receptacle?

Answer 7

The top of the pedical that supports the flower

Question 8

What is a sepal? (4)

Answer 8

1. Leaf like structure which protects the flower bud before it opens.
2. Often green so can photosynthesise
3. Can be coloured like the petals to attract insect pollinators
4. In wind pollinated plants they may be reduced in size.

Question 9

What is the Calyx?

Answer 9

Collective name for all the sepals

Question 10

What is a petal? (4)

Answer 10

1. Thin leaf like structure that is often coloured
2. Attracts pollinating insects
3. Protect sexual organs
4. Plants that use wind for pollination have much less showy flower parts

Question 11

What is the Corolla?

Answer 11

Collective name for all the petals

Question 12

What is the perianth?

Answer 12

This is the name for the calyx plus corolla

Question 13

What is a tepal?

Answer 13

In some plants, especially moncots, petals and sepals are unable to be distinguished easily. So they are known as tepals or perianth segments

Question 14

What is petalody

Answer 14

The metamorphosis of various floral organs (as stamens) into petals
e.g. Gardenia augusta

Question 15

What is the stamen? (2)

Answer 15

Male sexual organ. Made up of:
1. Anther - where pollen is produced
2. Filament - the stalk attaching anther to receptacle

Question 16

What is the androecium? (3)

Answer 16

Consists of:
1. Stamen
2. Anthers (and the pollen grains)
3. Filament

Question 17

What is the gynoecium? (3)

Answer 17

1. Ovary enclosing one or more ovules
2. Style
3. Stigma

Question 18

What is the carpel? (4)

Answer 18

Femal sex organ. Made up of:
1. Stigma - a sticky surface at the end of the style
2. Style - the organ that joins the stigma to the ovary
3. Ovary - The part of the carpel that contains the ovules. Has a thick wall that will develop into fruit after pollination
4. Ovule - the female sex cell. Will develop into seeds if fertilisation takes place

Question 19

What are the nectaries? (2)

Answer 19

1. Situated at the base of petals as a bait to bring in pollinators
2. Many flowers do not have nectaries

Question 20

What are perfect flowers?

Answer 20

Those flowers that have both male and female parts.
Also called entire or hermaphrodite

Question 21

What are imperfect flowers?

Answer 21

Flowers with only make OR female parts

Question 22

What are hermaphrodite plants?

Answer 22

Flowers that have both male and female parts (most species)

Question 23

What are monoecious plants?

Answer 23

Plants with seperate male and female on the same plant

Question 24

What are dioecious plants?

Answer 24

Male and female flowers on different plants

Question 25

Two examples of monoecious plants

Answer 25

1. Carpinus betulus
2. Betula pendula

Question 26

Two examples if dioecious plants

Answer 26

1. Salix alba
2. Ilex aquifolium

Question 27

What is pollination?

Answer 27

Pollination is the transfer of pollen (the male gamete of sex cell) from the anthers where it is produced to the stigma which is designed to recieve and recognised it.

Question 28

What is self-pollination? (3)

Answer 28

1. Pollen transfer within or between flowers on the same plant
2. Does not bring any new genetic material
3. Only with hermaphrodite or monoecious plants

Question 29

What is cross pollination? (3)

Answer 29

1. Pollen transfer between different plants
2. Dioecious plants have enforced cross pollination
3. Allows for genetic variation and improved selection

Question 30

Pollination details (4)

Answer 30

1. Pollen grains manufactured in the anther contain male gametes
2. Need to be transferred to stigma of receptive plant, generally of the same species
3. Chemical recognition signals are exchanged between pollen and plant on which the pollen lands.
4. If recognised the male gametes are able to move down the style to the ovary, where the male gamete can fuse with the female gamete within the ovule

Question 31

Characteristics of wind pollinated plants (7)

Answer 31

1. Flower small and inconspicuous
2. Petals often green
3. Rarely scented, nectaries are absent
4. Anthers loosely attached - the slightest movement initiates pollen release
5. Large amount of pollen produced
6. Pollen grains smooth and light
7. Large feathery stigmas hang outside the plant
   e.g.* Carpinus betulus*

Question 32

Characteristics of insect pollinated plants (8)

Answer 32

1. Flowers relatively large
2. Petals or bracts often brightly coloured
3. Flower may incorporate nectar guides or landing pads for larger insects
4. Often scented with nectaries
5. Anthers are smaller and remain inside the flower
6. Small amount of pollen produced
7. Pollen is often, larger, rough ir sticky in texture
8. Stigmas remain inside the flower, flat or lobed
   e.g. Digitalis purpurea

Question 33

What is hetrostyly? (3)

Answer 33

1. An adaptation to prevent self-pollination and ensure cross-pollination
2. Flowers are of two or three forms as regards to the length of stamens and styles so that the anthers and stigmas are at different levels
3. Pollen from a flower cannot reach the stigma of the same flower.

Question 34

Flowers favouring certain insects (2)

Answer 34

1. Antirrhinum majus - flower prevents entry of smaller insects and opens only to heavy bees that land on it
2. Arum italicum (arum lily) - trap pollinating insects for a period of time
3. Some flowers have nectar at the bottom of the flower so only long tongued insects an reach it

Question 35

Pollination problems

Answer 35

1. If weather is bad, bees dont fly and crops will be low
2. Wild flowers sometimes rely on one specific pollinator which can lead to loss of the plant of the insect becomes extinct
3. Commercial tomatoes rely on bees usually bumblebees to pollinate a crop
4. Not all vegetable need insects - some are self fertiles such as french beans

Question 36

What is an inflorescence?

Answer 36

A group of flowers clustered together is called an inflorescence.

Question 37

How is an inflorescence beneficial for pollination?

Answer 37

1. A mass of colourful flowers make a bigger impact than a single flower, so they can be more easily seen by their pollinator
2. Provide a landing stage for insects to walk over to collect nectar and pollen from many flowers with the least amount of energy expended (e.g in Sedum spectabile)
3. In wind-pollinated plants, the inflorescence enables the most efficient dispersal and entrapment of pollen, often in the form of catkins.
   (4. Inflorescence types are often characteristic for particular plant families so are a useful aid to identification.)