10. Plant Growth - Pukekohe High School

download report

Transcript 10. Plant Growth - Pukekohe High School

1 of 48
© Boardworks Ltd 2007
2 of 48
© Boardworks Ltd 2007
How are plants adapted to growth?
Different parts of a plant are adapted to assist its growth
and survival.
 Flowers are adapted
to enable reproduction.
 Stems support the plant
and transport nutrients.
 Leaves are adapted for
photosynthesis, which makes
materials for growth.
 Roots anchor the plant to the
ground. They also take up water
and minerals from the soil.
3 of 48
© Boardworks Ltd 2007
How tall can plants grow?
The tallest known plants are
the Coast Redwoods, found in
the USA. These grow to over
100 metres tall. That’s twice
the height of Nelson’s column!
The tallest native European
tree is the Caucasian Fir,
which can reach a height of
68 metres.
Eucalyptus trees imported
from Australia to Spain have
been known to grow to a
height of 80 metres.
4 of 48
© Boardworks Ltd 2007
How big can plants grow?
The Giant Sequoia, Sequoiadendron giganteum, does not
grow as tall as the Coast Redwood but it has a larger volume.
The largest, General Sherman, has a volume of almost
1,500 m3, about half the volume of an Olympic swimming pool.
5 of 48
© Boardworks Ltd 2007
What is the oldest plant in the world?
It is common for trees to live for
100 years but rare for animals to
live this long. Why?
Unlike animal cells, there is no
limit to the number of times plant
cells can divide and multiply.
Plant cells can differentiate to
form specific cells throughout the
plant’s life. Animal cells lose this
ability early in their life cycle.
Bristlecone pines, found in the
USA, are the oldest-known plants.
They can live for over 4,000 years.
6 of 48
© Boardworks Ltd 2007
What do plants need to grow?
This plant hasn’t been looked
after very well. What do plants
need to grow healthily?
 sunlight and an air supply
 water
 mineral nutrients.
If a plant cannot get these from
its environment, can it move to
somewhere else?
Plants are rooted to one place.
However, they can control their
direction of growth.
7 of 48
© Boardworks Ltd 2007
What controls plant growth?
Plants grow in response to
their environment.
The shoots of these tulips
grow upwards and the
roots grow downwards.
If a plant was unable to do
this it might not be able to
get enough water or sunlight
from its environment.
To what environmental
factors do plants respond
to make sure they grow
properly?
8 of 48
© Boardworks Ltd 2007
What do plants respond to?
Plants are very sensitive and their growth is affected by
their environmental conditions.
Any condition that affects plant growth is called a stimulus.
What are three types of stimuli that plants respond to?
light
water
gravity
Which stimulus will have the
strongest effect on the plant?
9 of 48
© Boardworks Ltd 2007
Which stimulus?
10 of 48
© Boardworks Ltd 2007
11 of 48
© Boardworks Ltd 2007
What is a tropism?
A tropism is a growth movement in response to a stimulus.
Plants grow towards or away from stimuli.
A growth movement towards a stimulus
is called a positive tropism.
What is growth away from
a stimulus called?
A growth movement away from a
stimulus is called a negative tropism.
Will all the parts of a plant respond
to a stimulus in the same way?
12 of 48
© Boardworks Ltd 2007
Are there different types of tropisms?
Plant responses to stimuli are given specific names:
light
water
gravity
phototropism
hydrotropism
geotropism
What do the names of each tropism mean?
Which parts of a plant respond to these different stimuli?
13 of 48
© Boardworks Ltd 2007
Defining tropisms
14 of 48
© Boardworks Ltd 2007
How do tropisms affect growth?
This plant does not have a
very straight stem. What
might have caused this?
The plant was placed on a
window sill and received light
from one direction only.
The shoots of plants grow
towards sunlight.
What is the name of this
type of plant response?
The response to sunlight
is called phototropism.
15 of 48
© Boardworks Ltd 2007
Phototropism experiment
16 of 48
© Boardworks Ltd 2007
Do plants have hormones too?
Like humans, plants use hormones,
(chemical messengers)
to control their development.
Hormones produced by plants
control growth, flowering and
fruit ripening.
The growth of shoots and roots is
controlled by a group of hormones
called auxins. These chemicals are
produced in the tips of the shoots
and roots.
What environmental stimuli might
cause a plant to produce auxins?
17 of 48
© Boardworks Ltd 2007
Hormones and phototropism
18 of 48
© Boardworks Ltd 2007
Discovery of auxins
19 of 48
© Boardworks Ltd 2007
Which way up?
How do plants always grow the right way up?
Plants respond to gravity to grow in the right direction.
20 of 48
© Boardworks Ltd 2007
Hormones and geotropism
21 of 48
© Boardworks Ltd 2007
How do roots respond to water?
Roots always grow towards water, which is a positive
tropism.
Roots will grow sideways, or even upwards, towards water.
Roots always have a stronger response to water than
gravity to ensure that a plant gets the water it needs.
22 of 48
© Boardworks Ltd 2007
How do roots and shoots respond to stimuli?
Plant stimuli affect certain parts of the plant in different ways.
 Shoots grow towards sunlight.
They are positively phototropic.
 Shoots grow away from gravity.
They are negatively geotropic.
 Roots grow away from sunlight.
They are negatively phototropic.
 Roots grow towards gravity.
They are positively geotropic.
What experiments can be used to test these ideas?
23 of 48
© Boardworks Ltd 2007
Tropisms and auxins – true or false?
24 of 48
© Boardworks Ltd 2007
25 of 48
© Boardworks Ltd 2007
How can plant hormones be used?
Plant hormones are naturally-occurring chemicals but they
can also be produced synthetically for use in gardening and
agriculture such as:
 growing cuttings
 ripening fruit
 killing weeds.
Why are these purposes useful for gardeners and farmers?
26 of 48
© Boardworks Ltd 2007
How are cuttings grown?
A cutting is a part of plant that is removed from the main
shoot. Do cuttings have everything they need to grow?
A cutting does not have roots and so has no supply of water
or minerals.
To stimulate root growth,
cuttings are dipped into
rooting powder. This
contains plant growth
hormones.
Cuttings are genetically
identical to the parent
plant. This allows growers
to copy successful plants.
27 of 48
© Boardworks Ltd 2007
Growing plant cuttings
28 of 48
© Boardworks Ltd 2007
How do plant hormones kill weeds?
Weeds are unwelcome plants that compete with the plants
being grown by gardeners and farmers.
However, many chemicals that are potential weedkillers are
toxic to animals and humans, as well as plants.
Plant hormones can be used
instead to make weedkillers
that only affect certain plants.
Most weeds have broad
leaves. Cereals, which have
narrow leaves, can be
protected from weeds by using
weedkillers that only effect the
growth of broadleaved plants.
29 of 48
© Boardworks Ltd 2007
How are hormones used to ripen fruit?
Fruit is often picked before it is fully ripe. Why might this
help keep the fruit edible?
Fruit often has to
travels thousands of
miles from where it is
picked to where it is
sold in the shops.
Unripe fruit is harder and
less likely to bruise than
ripe fruit when transported.
When the fruit reaches its destination, it can then be sprayed
with artificial plant hormones to encourage ripening.
Why might it be a good idea to wash fruit before eating it?
30 of 48
© Boardworks Ltd 2007
Which hormone makes fruit ripen?
Ethylene is a plant hormone that controls fruit ripening.
It can be sprayed on unripe fruit to speed up ripening.
Some fruit, such as bananas, actually
produce a large amount of ethylene, which
can cause other nearby fruits to ripen.
Using artificial ethylene to ripen
fruit is not just a modern practice.
Ancient Egyptians exposed figs to
natural gas, which contains
ethylene, to encourage ripening.
Why might it be important to keep fruit
away from coal-burning engines during
transportation?
31 of 48
© Boardworks Ltd 2007
32 of 48
© Boardworks Ltd 2007
What do plants need for a balanced diet?
Plants need carbon dioxide and water for photosynthesis.
Do they need any other nutrients to keep healthy?
33 of 48
© Boardworks Ltd 2007
What minerals do plants need?
Plants also need mineral ions for healthy growth.
Some of the most important minerals needed by plants are:
nitrogen
nitrates
phosphorus
phosphates
potassium
potassium ions
magnesium
magnesium ions
How do plants obtain these minerals?
The mineral ions are found in salts, dissolved in water.
Plants obtain minerals when they absorb water from the soil.
What type of salt are each of these elements found in?
34 of 48
© Boardworks Ltd 2007
What are minerals used for?
Mineral ions are used by plants for growth and to build new
cells.
Plants need a variety of minerals because they are used
by the plant in different ways.
How are the four key mineral ions used by plants?
Mineral element
How mineral is used in plants
nitrogen (N)
making proteins for growth
phosphorus (P)
respiration and making roots
potassium (K)
respiration and photosynthesis
magnesium (Mg)
making chlorophyll
35 of 48
© Boardworks Ltd 2007
How do minerals affect cell formation?
Minerals form the building
blocks of vital cell components:
 nitrogen is needed to make
amino acids and proteins
 phosphorus is needed to make
DNA and cell membranes
 potassium helps enzymes
work during photosynthesis
 magnesium is needed to
make chlorophyll.
What would happen to the plant if it
was not able to get these nutrients?
36 of 48
© Boardworks Ltd 2007
Which mineral?
37 of 48
© Boardworks Ltd 2007
What happens when plants do not get minerals?
Plants do not grow properly and begin to look unhealthy
if they are deprived of minerals.
If a plant does not get enough of a mineral it is said to
have a mineral deficiency.
Do all mineral deficiencies affect a plant in the same way?
38 of 48
© Boardworks Ltd 2007
Mineral deficiencies and plant growth
39 of 48
© Boardworks Ltd 2007
Mineral deficiency
40 of 48
© Boardworks Ltd 2007
Where do minerals come from?
What are the sources of minerals in the soil?
 Rocks. The minerals in rocks are
slowly dissolved by rainwater,
which is slightly acidic. These
minerals are washed into the soil.
 Natural fertilizers. Animal
faeces and the decay of dead
plants and animals return
minerals to the soil.
 Artificial fertilizers. These
contain a ready-made mixture of
the minerals needed by plants.
Why might farmers need to add fertilizers to their soil?
41 of 48
© Boardworks Ltd 2007
What are NPK values?
Fertilizers will often show NPK values on their labels.
What do you think these letters stand for?
NPK stands for nitrogen (N), phosphorus (P), and potassium
(K). Fertilizers contain these elements because plants need
these nutrients in higher quantities than other minerals.
The numbers show the percentage of each
mineral element. This fertilizer contains:
 15% nitrogen
 30% phosphorus
 15% potassium.
What percentage of each mineral is in a
fertilizer with the NPK value 20–10–5?
42 of 48
© Boardworks Ltd 2007
Artificial fertilizers
43 of 48
© Boardworks Ltd 2007
44 of 48
© Boardworks Ltd 2007
Glossary (1/2)
 auxins – Plant hormones that control the rate of growth.
 cutting – Part of a plant that has been removed from the
main shoot and does not have roots.
 ethylene – A plant hormone used to ripen fruit.
 geotropism – A growth movement in response to gravity.
 hydrotropism – A growth movement in response to water.
 mineral deficiency – A condition that occurs when a plant
is missing one or more of the minerals needed for growth.
 mineral ions – Naturally-occurring or synthetic chemicals
needed for healthy plant growth.
45 of 48
© Boardworks Ltd 2007
Glossary (2/2)
 mineral salts – Compounds containing essential plant
minerals.
 negative tropism – A growth movement away from a
stimulus.
 NPK value – The percentage of nitrogen, phosphorus and
potassium available in a fertilizer.
 phototropism – A growth movement in response to light.
 positive tropism – A growth movement towards a
stimulus.
 tropism – Any growth movement in response to a
stimulus.
46 of 48
© Boardworks Ltd 2007
Anagrams
47 of 48
© Boardworks Ltd 2007
Multiple-choice quiz
48 of 48
© Boardworks Ltd 2007