Lecture 8: Angiosperm breeding systems Flashcards
How much % of the seeds’ weight is water?
5-20%
true or false; seeds are usually dessicated when they are shed
true
What does a seed need to germinate?
water
oxygen
appropriate temperature
When is a seed considered dormant?
Even when the right germination conditions are provided, the seed does not germinate
What are the causes of dormancy?
- when the seed is immature when shed
- seed coat is impervious to water
What is the adaptation advantage of dormancy
- to ensure that the seed will germinate at the optimum time for growth
What is the breeding system
- the various morphological and physiological mechanisms (which are genetically controlled) that regulate the degree of cross and self fertilization in a population or species
true or false; most angiosperms are hermaphrodite and that plants are sessile
true
What are the three breeding systems of angiosperms
allogamous species
autogamous
apomictic
What does allogamous species mean
cross fertilizing or outbreeding: mating between genetically different plants
what does autogamous mean?
self fertilizing or inbreeding: mating between gametes of the same individual
What does apomictic mean?
a form of vegetative or asexual reproduction where seeds are still produced
What is the population structure of allogamous species
have population of highly heterozygous individuals and contain high levels of genetic variation due to intercrossing
What is the population structure of autogamous species
can have variable populations but the individual plants are homozygous; true breeding
What is the population structure of apomictic
have fairly uniform populations but individuals can be highly heterozygous
How do allogamous species maintain outbreeding
- ensuring that self pollination and self fertilization do not take place in hermaphrodite flowers
- separating the sexes into different flowers (monoecious) or plants (dioecious)
Define dichogamy
where the timing of male and female function is different: male first = protandry (protandrous)
female first: protogyny (protogynous)
What is herkogamy
- pattern of flower development
- spatial separation of male and female functions
What does approach herkogamy mean?
presentation of stigma above the level of the anthers
What is the effect of approach herkogamy
encourage floral visitors to make contact with the stigma ; before removing pollen from anthers
What does reverse herkogamy mean?
displayed when stigma is recessed below the level of anthers
What is the effect of reverse herkogamy
contact the anthers before the stigma
- more successful pollination
What does self incompatibility mean?
- 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
What is heteromorphic self incompatibility
- where we have different flower morphology associated with breeding system
- structure allows us to predict how a flower or plant will breed
