16 — reproduction in plants Flashcards
Petal
Petal — modified leaf that forms the most obvious part of a flower
Insect-pollinated flowers:
1. Petal brightly coloured with conspicuous modified leaves to attract insects for pollination
2. Prov a landing platform for insects
(All petals tgt make up the corolla)
Stamen
Male part of the flower that consists of an anther and a filament. Anther has 2 lobes, each contains 2 pollen sacs which produce pollen grains. The pollen grain contains 2 male gametes.
(All of stamens tgt make up the androecium (plural: androecia))
Filament
Holds anther in a suitable position to disperse pollen grains
(Pollen grains contains male gametes)
Anther
Produces pollen grains. It is made up of 2 lobes, each containing 2 pollen sacs. It consists of a vascular bundle made up of a phloem and a xylem.
Carpel
Female part of the flower. Consists of an ovary which contains ovules, a style through which pollen tube grows, and one or more stigmas which capture pollen grains.
All of the carpels tgt make up the pistil or gynoecium (plural: gynoecia)
Pollen grains
Hv a haploid set of chromosomes. Each pollen grain has 2 nuclei, the generative nucleus and the pollen tube nucleus or vegetative nucleus.
Stigma
Swollen structure that receives pollen grains. A mature stigma secretes sugary fluid to stimulate the germination of pollen grains.
The style connects the stigma to the ovary, and holds stigma in a suitable position to trap pollen grains
Style
Holds stigma in position to receive pollen grains
Ovary
Produces and protects the 1 or more ovules it contains. Becomes the fruit after fertilisation.
Ovule
Becomes the seed after fertilisation. The ovule contains the ovum and the definitive nucleus. The ovum has a haploid set of chromosomes. The ovule is attached to the placenta by a stalk called called the funicle.
Receptacle
Base of the flower where the other parts of the flower are attached
Sepal
Protects the flower during the bud stage.
Pollination
Pollination is the transfer of pollen grains from the anther of the male to the stigma of the female part of the flower
- Pollination is important to help
bring together the male and female
gametes to enable fertilisation to
take place. - Pollination can be brought about
by insects or wind. - There are two types of pollination:
1) Self-pollination
2) Cross-pollination
Self-pollination
Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or a different flower on the same plant.
- Flowers are bisexual with
anthers and stigmas
maturing at the same time. - The stigma is situated
directly below the anther. (Anther higher stigma lower) - Certain flowers in bisexual
plants never open
(cleistogamous) and only self-
pollination can happen.
Advantages of self-pollination
- Beneficial qualities are passed down from parent plant to offspring.
- Not dependent on external factors for pollination.
- More likely to take place since stigmas are closer to anthers.
- Less pollen and energy is wasted.
- Only one parent is required.