Reproduction in flowering plants
All living things need to produce more of their own kind to replace ones that die.
Flowering plants reproduce by making seeds.
The seeds are made in the FLOWER of the plant
The structure of a flower
Sepals: Green leaves around the outside of the flower. Sepals are usually smaller than the petals,. Used to protect the flower while it is still in bud.
Stamens: This is where pollen is made
It is the male part of the flower.
The stamen has two parts: the filament (a thin stalk) and the anther which is where pollen is made
Carpel: The carpel is the green stalk in the middle of the flower.
It is the female part of the flower.
The carpel has three parts:
At the top is the stigma. This is where pollen has to land.
Below the stigma is the style and then the ovary which is where seeds are formed
Sexual reproduction in a flowering plant has FOUR main stages
Before a seed can grow into a new plant they have to be fertilized by pollen.
Pollen comes from another plant during a process called pollination.
Pollination and fertilization take place in the flower of the plant.
Life Cycle of a flowering Plant
The seeds have to be moved away from the parent plant to prevent overcrowding and if the conditions are correct the seeds will germinate and eventually grow into a new adult plant which will make more seeds. Thie complete process forms the life cycle of the plant.
- Pollination: This is when pollen lands on a new flower
- Fertilization: This is when the pollen and the seed meet
- Seed dispersal: This is when the seed is spread around, away from the plant that made it
- Germination: This is when the seed, having reached the ground, starts to grow into a new plant
It is usually carried by bees (or other small animals) but it can be carried by the wind.
The seed also contains a food store, usually starch.
The part of the flower surrounding the seed is known as the fruit.
After fertilization the petals and stamens wither and die. The ovary (which forms the fruit) swells up, sometimes considerably. (ie as in the apple)
The job of the fruit is to carry the seeds as far as possible from the parent plant so the new plants have room to grow and do not compete for resources such as light, water and nutrients in the soil.
This process is called seed dispersal.
A plant will disperse their seeds four main ways:
1. The fruit is eaten by animals such as birds but are not digested. The seeds pass out the animal along with its droppings eg cherry, blackberry. These fruits look and taste nice.
2. The fruit splits open. sometimes this happens with a lot of force and the seeds are shot out. eg beans. the pod is the fruit and the beans are the seeds.
3. The fruits have little hooks. these hooks stick to the fur of animals. eg burdock.
4. The fruits have wings or hairs and this lets them get carried by the wind,. eg sycamore trees have winged fruits.
Conditions needed for germination
The seed will not germinate untill it gets warm. As well as warmth the seed also needs oxygen and water to grow.
Without all three (Water, oxygen and warmth) the seed will not grow.
The germination period is time between planting and starting to germinate.
Experiment to show how warmth effects the germination period
Three small pots had damp cotton wool placed in the base, with three bean seeds placed on each piece of cotton wool.
The pots were placed at the following locations:
- A warm, brightly lit window-sill,
- a closed refrigerator
- a warm dark airing cupboard.
The seeds were inspected and watered every day.
The time taken to germinate was recorded in each case.
|Window-sill:||warmth, light and water|
|Warm, dark cupboard||warm, no light and water|
|Refrigerator:||cold, no light and water;|
The seeds in the refrigerator took the longest to germinate (8 days)
The seeds on the window-sill and the seeds in the cupboard germnated quickly (3days)
This shows that warmth is necessary for germination.
Note that the seeds in the dark cupboard DID start to grow. This shows us that light is not needed for germination