chp 15: reproduction in plants [pure bio OLVL]

what is the definition of asexual reproduction?

Asexual reproduction is the process resulting in the production of genetically identical offspring from one parent without the fusion of gametes

what is the definition of asexual reproduction?

Sexual reproduction is the process of the fusion of two gametes to form a zygote resulting in the production of two genetically dissimilar offspring

what is the function of the sepal?

modified leaves protecting parts of the flower during the bud stage
what is the function of the petal?
modified leaves that are:
- brightly coloured and attractive to pollinators
- provide a platform for insects to land

what is the carpel/pistil?

the female part of a flower

what is the function of the stigma?

a swollen/feathery structure that receives pollen grain

what is the function of the style?

a stalk that connects the stigma to the ovary while holding the stigma in a suitable position to trap pollen grains

what is the function of the ovary?

- a structure that develops into a fruit after fertilisation
- produces and protects 1/more ovules (seed)

what is the stamen?

the male part of a flower

what is the function of the filament?

a stalk that holds the anther in a suitable position

what is the function of the anther?

containing two lobes

what is the definition of pollination?

the transfer of pollen grains from the anther to the stigma

what is a bisexual flower?

a flower that possesses both stamens and pistils

what is a unisexual flower?

a flower that possesses either stamen or pistil

what is a monoecious plant?

a plant that possesses both male and female unisexual flowers on the same plant

what is a dioecious plant?

a plant that possesses both male and female unisexual flowers on the same plant

what is the definition of self-pollination?

the transfer of pollen grains from the anther to the stigma of the same/different flower on the same plant

what are the features favouring self-pollination?

- flowers are bisexual with anthers and stigmas
- stigma and anther maturing at the same time
- stigma directly below/next to the anther
- anther close to the stigma --> higher probability of self-pollination

what are the advantages of self-pollination?

- only one parent plant is required
- the offspring inherits more beneficial qualities
- does not depend on external factors such as insects or wind or pollination
- less pollen and energy wasted

what are the disadvantages of self-pollination?

- fewer varieties of offspring are produced --> less adapted to changes in the environment
- higher probability of harmful recessive alleles being expressed --> weaker

what is the definition of cross-pollination?

the transfer of pollen grains from the anther to the stigma in another plant of the same species

what are the features favouring cross-pollination?

- dioecious plants bear either male or female flowers
- anther and stigma mature at different times (bisexual flowers)
- the stigma and anther are far away from each other

what are the advantages of cross-pollination?

- offspring may have inherited beneficial qualities from both parents
- more varieties of offspring --> greater genetic variation
- increased chance of surviving changes in the environment --> more viable seeds produced
- lesser likelihood of harmful recessive alleles being expressed

what are the disadvantages of cross-pollination?

- 2 parents are required
- depends on external factors (wind/insect)
- lesser probability --> must have pollen grain go to a different flower

post-pollination

1. After pollination, the pollen grain germinates in response to the fluid secreted by the mature stigma
2. The pollen tube nucleus controls the formation of the pollen tube that grows out of the pollen grain
3. Enzymes secreted by the pollen tube nucleus continues to digest the surrounding tissues of the stigma and style and penetrates through the style as it grows
4. The cytoplasm, pollen tube nucleus and generative nucleus of each pollen grain pass through the pollen tube
5. The generative nucleus divides by mitosis into 2 male nuclei
6. The pollen tube enters the ovule through an opening in the ovule wall called the micropyle
7. The pollen tube disintegrates
8. One male nuclei fuses with the ovum to form a zygote. Fertilisation has occurred