In order to reproduce flowering plants produce seeds.
Seeds contain nearly everything required to start the growth of a new plant.
A seed is made up of the embryo a food supply (endosperm) both enclosed in a tough seed coat (testa).
Seeds can survive for many years in the ground.
They appear to be dead.
When conditions are suitable they burst into life and start the growth of a new plant.
This is called germination.
4 Germination What is needed for germination to be successful How do we find out Investigate!! 5 Investigation
When setting up an investigation we need to change something and this is called a variable
We start by setting up the basic apparatus
In this case it will look like this
Our variables will be
So we now want our investigation to be 5 boiling tubes
1. No light
2. No water
3. No heat
4. No oxygen
5. Everything (the control)
So just what do seeds need for germination
8 Structure of a Flower
Sexual reproduction occurs in plants as well as animals.
The FLOWER contains the reproductive organs of a plant.
Flowers of different plants may not be exactly alike but they are built to the same basic plan.
9 Structure of a Flower 10 Structure of a Flower 11 Structure of a flower
Pollen is made inside the anthers.
When they ripen the pollen is released.
Pollen grains are like specks of dust.
They contain the MALE sex cell.
This has to reach the egg cell (ovule) in the ovary.
Pollination is the transfer of pollen from the anthers of one plant to the stigma of another.
Most flowers rely on either the wind or insects to transfer their pollen
It is often easy to tell the method of pollination used by a flower by its appearance.
Insect pollinated flowers use animals such as bees butterflies birds bats.
Wind pollinated flowers have structures which make use of the wind.
14 Methods of Pollination 15 Insect pollination e.g. Passion flower 16 Wind Pollination e.g. Sedge 17 Fertilisation
Once the pollen has landed on the stigma the male sex cell inside has to get to the female sex cell.
To do this it has to grow a pollen tube down through the style.
The stigma produces a sugary fluid to feed the growing pollen tube.
18 Fruit Formation
After fertilisation the fertilised ovule becomes the seed
The ovary develops into the fruit
The fruits can help in seed dispersal depending on what kind of fruit they are.
There are 2 kinds
Dry fruits e.g. poppy lupin dandelion sycamore etc
Flesh fruits e.g. tomatoes plums gooseberries etc
19 Seed Dispersal
Once fertilisation has taken place the flower withers and a seed and fruit are formed from the ovary.
The seeds must be scattered as far away from the parent plant as possible.
This avoids the new plants competing with the parent for vital resources.
This seed dispersal is achieved in a variety of ways.
20 Animal (external)
Seeds can be dispersed by animals.
The seed has hooks which catch onto animals fur and are transported by the animal until they fall off and hopefully germinate elsewhere.
21 Animal (internal)
Seeds can also be eaten by animals along with the fruit.
The seeds pass through the animal and are deposited in the droppings elsewhere
22 Wind Dispersal
Plants can also use the wind to scatter their seeds and they use different mechanisms to achieve this.
E.g. the poppy uses the pepper pot method
23 Wind Dispersal
Ragwort dandelions cotton etc. use the parachute method.
Each seed has a number of small feather-like structures to help it float in the wind.
24 Wind Dispersal
Some seeds have wings to help them fly in the wind.
E.g. sycamore ash etc..
Some plants such as peas and gorse use pods which explode to fire the seeds away from the parent.
As a pod dries tensions are set up in the wall of the pod eventually causing it to split along two lines of weakness.
26 Plant Life Cycle SEED POLLINATION GERMINATION FLOWERS STEMS ROOTS 27 Plant Life Cycles
All stages involved in plant reproduction take place continually year after year.
Some plants can reproduce WITHOUT forming seeds.
This is another form of reproduction
It only involves one parent
No sex cells are involved
It is called ASEXUAL reproduction
28 Plant Life Cycles
During asexual reproduction the parent plant produces new cells which eventually separate and become new independent plants.
E.g. strawberry spider plant etc..
29 Plant Life Cycles The Mexican Hat Plant produces plantlets around the edge of the leaves. These eventually fall off and develop into new independent plants. 30 Asexual Reproduction
Asexual reproduction is quite common in plants
It produces new plants with the same characteristics as the parent.
There is no variation
If the plant is resistant to a particular disease then so will the offspring.
31 Asexual Reproduction
Plants produced in this way are often found growing in clumps to reduce competition from other plants.
Growth occurs very quickly because of available food store.
It is successful as it does not involve the vulnerable stages of germination and early seedling growth.
Plants which are all identical formed in this way are called a CLONE
32 Sexual Asexual Reproduction There are some important differences between these 2 methods of reproduction. Each method has advantages and disadvantages. 33 Artificial Propagation
Gardeners make use of a plants ability to reproduce asexually by using a method known as artificial propagation.
Instead of growing seeds they take a small section of stem root or leaf and under the right conditions these will grow into a full plant.
34 Taking Cuttings Take a piece 100-150 mm long by snipping (a tip cutting - a) or by tearing off a side shoot (a heel cutting - b). Remove all flowers and buds and all leaves to about half way up the stem. 35 Taking Cuttings Slice a small sliver of bark off the bottom 5 mm of tip cuttings (a) or carefully trim the end of heel cuttings (b). Make holes with a pencil or knitting needle in damp potting mix in a small clean pot. A suitable mix is a mixture of 75 washed river sand and 25 sieved peat moss (or preferably an environmentally-friendly peat alternative such as Coco Peat). 36 Taking Cuttings Dip the prepared end of the cutting into a root -promoting hormone powder blow off the excess place in the hole in the damp sand to about half its length and press the sand firmly around the cutting. Root-promoting hormones should be kept in a refrigerator when not being used and are also available as liquids or gels. Place the pot of cuttings into a plastic ice-cream container (or similar) with a little damp sand or peat-moss in the bottom cover with a plastic bag and seal with an elastic band or sticky tape. 37 Grafting 38 Grafting 39 Layering
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