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The World of Plants

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E.g. strawberry, spider plant, etc.. Plant Life Cycles ... Plants produced in this way are often found growing in clumps to reduce ... – PowerPoint PPT presentation

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Title: The World of Plants


1
The World of Plants
  • Growing Plants

G Davidson
2
Structure of a seed
  • 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).

3
Germination
  • 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

6
Investigation
  • Our variables will be
  • Water
  • Light
  • Heat
  • Oxygen
  • 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)

7
Germination
  • So, just what do seeds need for germination?
  • Water
  • Oxygen
  • Minimum temperature

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.

12
Pollination
  • Pollination is the transfer of pollen from the
    anthers of one plant to the stigma of another.

13
Pollination
  • 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.
  • E.g. Burdock

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
  • E.g. bramble

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..

25
Explosive
  • 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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