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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.


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.


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

1,500m3, about half the volume of an Olympic swimming pool.


What is the oldest plant in the world?

Bristlecone pines, found in the

USA, are the oldest-known plants.

They can live for over 4,000 years.

Unlike animal cells, there is no

limit to the number of times plant

cells can divide and multiply.

It is common for trees to live for

100 years but rare for animals to

live this long. Why?

Plant cells can differentiate to

form specific cells throughout the

plant’s life. Animal cells lose this ability early in their life cycle.


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.


What controls plant growth?

Plants grow in response to

their environment.

The shoots of these tulips

grow upwards and the

roots grow downwards.

To what environmental

factors do plants respond

to make sure they grow

properly?

If a plant was unable to do

this it might not be able to

get enough water or sunlight

from its environment.


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.

light water gravity

Which stimulus will have the

strongest effect on the plant?

What are three types of stimuli that plants respond to?


Which stimulus?



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.

A growth movement away from a

stimulus is called a negative tropism.

What is a tropism?

Will all the parts of a plant respond

to a stimulus in the same way?

What is growth away from

a stimulus called?


Plant responses to stimuli are given specific names:

What do the names of each tropism mean?

water gravitylight

hydrotropism geotropismphototropism

Which parts of a plant respond to these different stimuli?

Are there different types of tropisms?


Defining tropisms


How do tropisms affect growth?

This plant does not have a

very straight stem. What

might have caused this?

The shoots of plants grow

towards sunlight.

The plant was placed on a

window sill and received light

from one direction only.

What is the name of this

type of plant response?

The response to sunlight

is called phototropism.


Phototropism experiment


Do plants have hormones too?

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.

Like humans, plants use hormones,

(chemical messengers)

to control their development.

Hormones produced by plants

control growth, flowering and

fruit ripening.

What environmental stimuli might

cause a plant to produce auxins?


Hormones and phototropism


Discovery of auxins


Which way up?

How do plants always grow the right way up?

Plants respond to gravity to grow in the right direction.


Hormones and geotropism


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.

How do roots respond to water?


How do roots and shoots respond to stimuli?

Shoots grow towards sunlight.

They are positively phototropic.

Plant stimuli affect certain parts of the plant in different ways.

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?


Tropisms and auxins – true or false?



growing cuttings

killing weeds.

ripening fruit

Why are these purposes useful for gardeners and farmers?

Plant hormones are naturally-occurring chemicals but they

can also be produced synthetically for use in gardening and

agriculture such as:

How can plant hormones be used?


A cutting is a part of plant that is removed from the main

shoot. Do cuttings have everything they need to grow?

How are cuttings grown?

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.


Growing plant cuttings


Weeds are unwelcome plants that compete with the plants

being grown by gardeners and farmers.

How do plant hormones kill weeds?

Plant hormones can be used

instead to make weedkillers

that only affect certain plants.

However, many chemicals that are potential weedkillers are

toxic to animals and humans, as well as 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.


Fruit often has to

travels thousands of

miles from where it is

picked to where it is

sold in the shops.

How are hormones used to ripen fruit?

When the fruit reaches its destination, it can then be sprayed

with artificial plant hormones to encourage ripening.

Fruit is often picked before it is fully ripe. Why might this

help keep the fruit edible?

Unripe fruit is harder and

less likely to bruise than

ripe fruit when transported.

Why might it be a good idea to wash fruit before eating it?


Which hormone makes fruit 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.

Ethylene is a plant hormone that controls fruit ripening.

It can be sprayed on unripe fruit to speed up ripening.

Why might it be important to keep fruit

away from coal-burning engines during

transportation?

Some fruit, such as bananas, actually

produce a large amount of ethylene, which

can cause other nearby fruits to ripen.



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?


What minerals do plants need?

Plants also need mineral ions for healthy growth.

Some of the most important minerals needed by plants are:

The mineral ions are found in salts, dissolved in water.

Plants obtain minerals when they absorb water from the soil.

How do plants obtain these minerals?

nitrogen

potassium ions

phosphorus

potassium

magnesium magnesium ions

phosphates

nitrates

What type of salt are each of these elements found in?


Mineral ions are used by plants for growth and to build new

cells.

making proteins for growth

respiration and making roots

respiration and photosynthesis

making chlorophyll

Mineral element How mineral is used in plants

nitrogen (N)

phosphorus (P)

potassium (K)

magnesium (Mg)

What are minerals used for?

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?


How do minerals affect cell formation?

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.

Minerals form the building

blocks of vital cell components:

What would happen to the plant if it

was not able to get these nutrients?


Which mineral?


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.

What happens when plants do not get minerals?

Do all mineral deficiencies affect a plant in the same way?


Mineral deficiencies and plant growth


Mineral deficiency


Where do minerals come from?

Rocks. The minerals in rocks are

slowly dissolved by rainwater,

which is slightly acidic. These

minerals are washed into the soil.

What are the sources of minerals in the soil?

Why might farmers need to add fertilizers to their 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.


30% phosphorus

15% nitrogen

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.

What percentage of each mineral is in a

fertilizer with the NPK value 20–10–5?

The numbers show the percentage of each

mineral element. This fertilizer contains:

15% potassium.


Artificial fertilizers



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.


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.


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Multiple-choice quiz

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