Lecture 8: Angiosperm breeding systems

Question 1

How much % of the seeds’ weight is water?

Answer 1

5-20%

Question 2

true or false; seeds are usually dessicated when they are shed

Answer 2

true

Question 3

What does a seed need to germinate?

Answer 3

water
oxygen
appropriate temperature

Question 4

When is a seed considered dormant?

Answer 4

Even when the right germination conditions are provided, the seed does not germinate

Question 5

What are the causes of dormancy?

Answer 5

• when the seed is immature when shed

- seed coat is impervious to water

Question 6

What is the adaptation advantage of dormancy

Answer 6

• to ensure that the seed will germinate at the optimum time for growth

Question 7

What is the breeding system

Answer 7

• the various morphological and physiological mechanisms (which are genetically controlled) that regulate the degree of cross and self fertilization in a population or species

Question 8

true or false; most angiosperms are hermaphrodite and that plants are sessile

Answer 8

true

Question 9

What are the three breeding systems of angiosperms

Answer 9

allogamous species
autogamous
apomictic

Question 10

What does allogamous species mean

Answer 10

cross fertilizing or outbreeding: mating between genetically different plants

Question 11

what does autogamous mean?

Answer 11

self fertilizing or inbreeding: mating between gametes of the same individual

Question 12

What does apomictic mean?

Answer 12

a form of vegetative or asexual reproduction where seeds are still produced

Question 13

What is the population structure of allogamous species

Answer 13

have population of highly heterozygous individuals and contain high levels of genetic variation due to intercrossing

Question 14

What is the population structure of autogamous species

Answer 14

can have variable populations but the individual plants are homozygous; true breeding

Question 15

What is the population structure of apomictic

Answer 15

have fairly uniform populations but individuals can be highly heterozygous

Question 16

How do allogamous species maintain outbreeding

Answer 16

• ensuring that self pollination and self fertilization do not take place in hermaphrodite flowers
• separating the sexes into different flowers (monoecious) or plants (dioecious)

Question 17

Define dichogamy

Answer 17

where the timing of male and female function is different: male first = protandry (protandrous)
female first: protogyny (protogynous)

Question 18

What is herkogamy

Answer 18

• pattern of flower development

- spatial separation of male and female functions

Question 19

What does approach herkogamy mean?

Answer 19

presentation of stigma above the level of the anthers

Question 20

What is the effect of approach herkogamy

Answer 20

encourage floral visitors to make contact with the stigma ; before removing pollen from anthers

Question 21

What does reverse herkogamy mean?

Answer 21

displayed when stigma is recessed below the level of anthers

Question 22

What is the effect of reverse herkogamy

Answer 22

contact the anthers before the stigma

- more successful pollination

Question 23

What does self incompatibility mean?

Answer 23

• the inability of a plant to set seed when pollinated with its own or genetically similar pollen
• involves a recognition reaction between stigma or style and pollen that identifies the pollen genotype
• very common in angiosperms, not found in other plant groups, but present in fungi

Question 24

What is heteromorphic self incompatibility

Answer 24

• where we have different flower morphology associated with breeding system
• structure allows us to predict how a flower or plant will breed

Question 25

true or false; heteromorphic SI species can also show differences in pollen wall ornamentation and stigma surfaces

Answer 25

true

Question 26

What is the genotype of a thrum and pin of a hetero SI usually

Answer 26

thrum: heterozygous Ss
pin: homozygous ss
- 1:1 ratio in progeny

Question 27

What does the S gene stand for?

Answer 27

controls style length, anther height, stigma and pollen morphology as well as the recognition or rejection reaction

Question 28

What does homomorphic incompatibility mean?

Answer 28

• there is no difference in flower morphology linked to breeding behaviour
• must carry out breeding experiments to identify mating types
• have two types: gametophytic where mating type is controlled by genotype of pollen and sporophytic where it is controlled by the parent plant

Question 29

How does recognition reaction work?

Answer 29

• recognition reaction is like the human immune system but in reverse
• recognition molecules are present in the pollen tube or pollen grain wall and stigma surface or stylar tissue
• very complex system that differs between sprophytic and gametophytic SI
• can simply demonstrate this by amputation experiments or pollination of immature stigma