Reproduction in Plants Flashcards
What is a dicotyledon?
A plant that produces seeds that contain two cotyledons; they have two primary leaves.
What is an insect-pollinated flower?
A type of flower that relies on an insect transferring pollen grains between flowers.
Name the main components of an insect-pollinated flower.
Anther
Style
Stigma
Pedicel
Receptacle
Ovary
Petal
Filament
Sepal
What is the calyx?
Leafy structures when the plant is first formed in order to protect the flower during it’s development.
What is the corolla?
All the petals of a flower
What is the carpel?
The female part of the plant consisting of a stigma, a style and an ovary
What is the stamen?
Male part of the plant which consists of the anther and the filament which is involved in the production of male gametes in the form of pollen grains.
Describe the adaptations of insect-pollinated plants
Internal anthers and small stigma directly touch insects
Large, bright petals and nectar from glands attract insects
May produce chemicals to the mimic scent of female insects or to intoxicate insects
Grow individually
Large pollen grains, sometimes with projections that attach to insect
What is a wind-pollinated plant?
A type of flower that relies on wind to transfer pollen grains between flowers.
Describe the adaptations of wind-pollinated plants.
External anthers optimise pollen dispersal
Excess pollen compensates for wind wastage Feathery stigma catches pollen from the air
Small, dull petals (no need to attract insects)
Grow densely over large areas
Light pollen grains
How does a pollen grain form in the anther?
- Large numbers of pollen mother cells produced by mitosis
Meiosis of diploid mother cells in the anther forms four haploid microspores - Haploid microspores mature into pollen grains via mitosis
Describe the role of the tapetum in pollen grain development.
- Specialised layer of cells in the anther
- Provides nutrients to developing pollen
grains
Describe the structure of mature pollen grains.
Generative cell (haploid nucleus) produces two male gametes via mitosis
Pollen tube cell (also has its own nucleus) elongates to penetrate ovule
Outer protective coating
Define dehiscence.
The splitting of the anther resulting in the release of pollen grains.
How does the ovule form in the ovary?
Meiosis of megaspore cell produces four haploid megaspores
Growth and development (involving three mitotic divisions) of one of the megaspores
Embryo sac forms containing eight haploid nuclei
Describe the structure of the embryo sac.
Two polar nuclei form endosperm
Ovum forms zygote
Two synergids help generative nucleus of pollen grain to reach ovum
Three antipodal cells
Outer protective coating