Download Subtopic(b) Growing plants

World of Plants
Sub topic (b) Growing plants
Seed structure
• Plants reproduce by
making seeds.
• Seeds contain an
embryo and a food
store.
• Seeds are covered by
a tough seed coat.
Broad bean seed - opened up
Food store
Embryo plant
Seed coat
Parts of the seed
• The embryo will grow
into the new plant.
• The food store
provides energy for
the growth of the new
plant.
• The seed coat
protects the seed
while it is in the soil.
Seed coat
Embryo plant
Food store
Dissected broad bean seed
Germination
• Germination is the
growth of a seed.
• During germination,
a seed uses its food
store for energy.
• Plants can make
their own food
when they have
grown their first
leaves.
Tomato seedlings, grown from
seeds
Investigation
• When setting up
an investigation
we need to
change
something and
this is called a
‘variable’
Seeds
• We start by
setting up the
basic apparatus
• In this case it will Cotton wool
look like this:
Boiling
tube
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. Has all four variables (acts as the control)
Results
•
•
•
•
•
Tube 1 ( no light) - germinates
Tube 2 (no water) - no germination
Tube 3 ( no heat) – no germination
Tube 4 ( no oxygen) – no germination
Tube 5 (control) - germinates
Conditions for germination
• Seeds need warmth – a
minimum temperature,
oxygen and water if they
are to germinate. (WOW)
If any one of these factors
is missing, the seeds will not
germinate.
• (Seeds don’t need light to
germinate, but new
seedlings need it after
germination.)
Germinating broad bean
seed
( it doesn’t matter which way
up the seed is put- the roots
will grow down and the stem
will grow up!)
Effect of temperature (C)
• Seeds don’t
germinate in cold
temperatures
• % germination
increases the
temperature rises
and most
germination occurs
at the optimum
temperature
• Above the optimum
temperature %
germination
decreases because
enzymes are being
denatured
Structure of a Flower
• Sexual reproduction occurs in plants as
well as animals.
• The FLOWER contains the reproductive
organs of a plant.
• Flowers contain the male and female sex
cells for reproduction.
• Flowers of different plants may not be
exactly alike, but they are built to the same
basic plan.
Different kinds of flowers
Epiphyllum
Maricopa
A wild strawberry
Flower
Lily flower
Stigma
Anther
Filament
Bright petals
Carpel - female part of flower
1
2
5
3
4
Stamens
Anther
• Stamens are the male
parts of flowers - they
consist of an anther and
filament
• The anther produces
pollen grains which
contain the male gamete
• The filament supports
the anther
Filament
Basic Structure of a flower
1
stigma
2
8
3
style
7
petals
anther
filament
Ovary + ovule
6
4
5
sepals
nectary
Function of flower structures
Structure
Function
Sepal
1
Protects the flower when it is in bud
Petal
Attracts insects to flowers by their
bright colour 2or scent
3
Nectary
Contains sugary liquid called
nectar
Stamen -Anther
4
Makes pollen grains, which contain
the male sex cell
-Filament
Carpel -Stigma
Supports the anther
6
-Ovary
-Ovules
Sticky to catch
5 the pollen grains
Contains ovules
Contain the7female sex cell
Pollen
• Pollen is made inside the anther
• Pollen grains contain the male sex cell
Unripe Anther
Ripe anther splits
open releasing pollen
Pollen grains from different
plants
Ragweed
Chamomile
Willow tree
• Pollen grains are like thumb prints – no two are
the same!
Pollination
•Pollination is the
transfer of pollen
from anther to the
stigma
•There are two
methods of
pollination
•Wind Pollination
•Insect Pollination
Insect pollinated flower
• Insect pollinated
flowers have
• Brightly coloured
and scented petals
to attract insects
• Insects feed on
the sugary nectar
How are these
flowers different?
Wind pollinated flower•Wind pollinated
flowers have
Feathery stigmas
•Small dull flowers
•Stigmas and
stamens hang out
Large stamens
hang out
Methods of Pollination
Insect pollination
Have a 1scent
Wind pollination
No scent
Sticky, spiky pollen
Large amounts of light
2
pollen
Sticky stigma inside Feathery stigmas hang
3
flower
outside the flower
Stamens surrounded Large stamens hang
4
by petals
outside flower
5 nectar
Produce
Don’t produce nectar
Petals large & bright Petals small
6 & dull
Insect Pollination Methods(C)
Structure
Explanation
Brightly coloured
petals 1
Scented petals
Nectar 3
Spiky sticky pollen
Sticky stigma inside
5
flowers
Stamens surrounded
by petals
Attracts insects
Attracts insects
2
Attracts insects
sticks to4insects
Insects leave pollen behind
when they visit a flower
Insects crawl into flower to
6
get nectar and
pick up
pollen
Wind Pollination Methods (C)
Structure
Explanation
Petals small and dull
Don’t attract insects
1
Large amounts of
light pollen
Easily blown
in wind
2
Feathery stigmas
hang out3of flower
Stigmas have a large
surface area to catch
pollen in wind
Pollen blown
away in
4
wind
Large stamens hang
out of flower
Fertilisation (C)
• Once the pollen has landed on
the stigma the male sex cell
inside has to get to the female
sex cell inside an ovule.
• To do this it grows a pollen tube
down through the style
• The pollen tube grows through
the ovary wall and into an ovule.
• The male gamete travels down
the pollen tube and enters ovule
• In the ovule the nucleus of the
male gamete fuses with the
female nucleus
• Each fertilised ovule becomes a
seed
1
2
3
4
Seed and fruit formation.
• The flower is pollinated by an insect or
wind, after this the pollen tube grows
and fertilisation occurs.
• After fertilisation the ovule becomes a
seed.
• After the seed has formed the ovary wall
swells up and becomes a fruit (and the
petals, sepal stigma and style all die).
Seed dispersal (C)
• Why do plants have to
disperse (scatter) their
seeds?
• Stops new plant having to
compete with the parent
plant for :
• Water / Nutrients / Root space
• There are three methods of
seed dispersal
• Wind
• Animal External
• Animal Internal
Wind dispersal (C)
• These seeds have wings
or parachutes so that
they can be carried
away by the wind e.g.
dandelion and
sycamore / ash
dandelion
ash
sycamore
Animal External (C)
• These seeds have
hooks which attach
themselves to the fur of
animals.
• As the animals move
about the seeds fall off.
• e.g. cleavers (sticky
willy)
Wood avens
Cleavers
Animal internal (C)
• These fruits are brightly
coloured and juicy so
that they attracts
animals and make them
want to eat them.
• The seeds are
undigested by the
animals and are passed
out in the animals
faeces.
• e.g. cherry or tomato
Cherry seeds in faeces
Cherry seeds
Plant Propagation
• Plants can be
propagated naturally
without using seeds and
sexual reproduction. The
plant will make copies of
itself using asexual
reproduction e.g. runners
or tubers .
• Or propagation might be
artificial - gardeners can
make new plants in a way
that the plant is unable
to do naturally - for
example, cuttings and
grafting.
Tuber
Cutting
Asexual Reproduction
•
Asexual reproduction is the production of
genetically identical offspring from a
single parent
• There are two methods of natural
asexual reproduction used by plants
1. Runners – e.g. spider plant / strawberry
2. Tubers – e.g. potato plant
Asexual Reproduction - tubers
• Tubers are
underground stems
or roots that are
swollen with food.
• Each tuber can
grow into another
plant the next
year, using food
stored in the tuber
to start it off.
New potato plant
growing from one of
last year’s tubers.
New tubers will form
on underground stems.
tuber
Asexual Reproduction -Runners
• Some plants produce
plantlets at the end of
long stems that ‘run’
along the ground.
• The plantlets will get food
and water from the
‘parent’ plant until they
have grown roots into the
soil.
• Then the stem will wither
away and the plantlet will
grow on its own.
Spider plant
runner
runner
plantlet
Artificial Propagation
• Artificial propagation is the production of
plants by humans
• It involves asexual reproduction and so the
new plants are genetically identical
• There are two methods of artificial
propagation
• Cuttings e.g. geranium / busy lizzie
• Grafting e.g. fruit trees / rose trees
Artificial Propagation -Cuttings
• Gardeners can take
cuttings from plants.
• The plants will regrow roots if the cut
end is put in moist
compost or water
for a couple of
weeks.
• Rooting powder can
be put onto the cut
end to encourage
root growth.
• Then the cutting can
be planted in soil or
compost.
Stem cutting
placed in water.
Two weeks later it
has grown roots.
Reducing water loss
• A new cutting loses water
through its leaves but
doesn’t have any roots to
take up more water.
• So gardeners often remove
lower leaves from a cutting
to reduce water loss.
• Cuttings can be kept under
a plastic bag. This reduces
water loss too because it
makes the air around the
plant humid (damp).
Artificial propagation - grafting
• Grafting is a method of
propagating fruit trees and
rose bushes.
• A cutting (scion) is taken from
a delicate cultivated variety
• The scion is grafted onto the
root stock of a hardy variety
• The join is bound together
with tape
Cutting (scion)
Root stock
Grafting
scion
Root stock
join
Advantages of Artificial propagation (C)
• Once a new variety of plant has been produced
by sexual reproduction it can be artificially
propagated
• Advantages of artificial propagation
• Rapid production of new plants
• All plants will have the same desirable
characteristics
• Sterile / weak varieties of plants can be
reproduced
• Rare plants can be conserved
Asexual reproduction (C)
• Advantages – when a plant reproduces
asexually there are the following advantages
• There is no variation – offspring are
genetically identical (a clone)
• Vulnerable stages of sexual reproduction are
avoided e.g. pollination
• Rapid colonisation / growth
• Offspring obtain food and water from parent
Clone (C)
• All plants produced
by asexual
reproduction or
artificial propagation
form a clone
• A clone has no
genetic variation
• Offspring and parent
in a clone are
genetically identical
• Disadvantages of
asexual reproduction
• Overcrowding
• Bad characteristics
passed on
• Not widely dispersed
Advantages of sexual
reproduction (C)
• Sexual reproduction involves the fusion
of gametes resulting in new genetic
combinations. It has the following
advantages
• New varieties can be produced
• Can survive a change in conditions
• Seed dispersal allows plants to spread to
new habitats
Disadvantages of sexual
reproduction (C)
• Sexual reproduction can be considered
to have the following disadvantages
• Has vulnerable stages e.g. pollination,
germination and seed dispersal which
are not guaranteed to take place
• Produces variation – a plant grower may
want the new plants to have guaranteed
uniformity ( all the same)