Learning outcomes:
3.1
understand the differences between sexual and asexual reproduction
3.2
understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo
3.3
describe the structures of an insect-pollinated and a wind-pollinated flower and explain how each is adapted for pollination - b
3.4
understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formation
3.5
understand the conditions needed for seed germination
3.6
understand how germinating seeds utilise food reserves until the seedling can carry out photosynthesis
3.7
understand that plants can reproduce asexually by natural methods (illustrated by runners) and by artificial methods (illustrated by cuttings)
There are two types of reproduction;

Sexual: reproduction in which two gametes (sex cells) fuse to create a new offspring that is genetically different to the parents. Two parents are involved.
Asexual: reproduction without fusion of gametes. It involves one parent only and produces offspring that are genetically identical to the parent.

Two definitions to learn:

Fertilization: the process in which a male and a female gamete fuse to form a zygote
Zygote: a cell that is the result of fertilization. It will divide by mitosis to form an embryo.

Reproduction in Flowering plants:
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Part - Function
Petal - Colourful part of the flower. Attracts insects in insect-pollinated plants
Anther - Male part of the plant. Makes pollen.
Filament - Joins the anther to the rest of the flower.
Stigma - Female part of the plant. Receives pollen.
Ovary - Contains the ovules
Ovule - Eggs – female gametes
Pollen - Male gamete
Nectary - Makes nectar to attract insects in insect-pollinated plants
Sepal - Protects the flower when it is in bud

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Image by Ray Husthwaite

Wind Pollinated
- Anthers are large and outside the flower
- Stigma is large and outside the flower
- Tiny colourless petals
- Pollen made in huge quantities
- No nectary

Insect Pollinated
- Anthers are small and inside the flower
- Stigma is small and inside the flower
- Large colourful petals
- Has a nectary

Pollination: the deposition of pollen from the anther of one flower onto the stigma of a different flower of the same species. When pollination occurs, the pollen grows a pollen tube down the stigma of the flower. The pollen tube carries the nucleus of the pollen into the ovary, where it fuses with an ovule (fertilisation).

When fertilization has happen the flower will change in the following ways;
1. Petals die and fall away
2. Fertilized ovule turns into a seed
3. Ovary may fill with sugars and turn into a fruit

In order to germinate (grow into a new plant) seeds need the following conditions;
- Presence of water
- Presence of O2 (seed needs to respire)
- Correct temperature (recall enzymes work at optimum temp)

When a seed germinates the cells inside it start to grow rapidly and form the new shoot and root. The seed contains a limited store of carbohydrate and lipid, which it uses as a fuel for respiration to provide the energy for growth. During this stage the seed must produce leaves so it can begin to photosynthesize. The danger is that the seed will run out of stored energy before it makes leaves. If this happens it will die.

Plants can also reproduce asexually;

Natural methods

Runners – a root from one plant grows a separate shoot, which grows into a new plant. Eventually the original root connecting the two plants breaks down, separating the plants.
See also rhizomes, corms, bulbs and tubers (not mentioned on syllabus).

Artificial methods

Cuttings – a branch from one plant is removed and planted in soil. It will grow new roots and become a new plant.
See also grafting (not mentioned on syllabus)

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