The important roles of the different parts of plants...The important roles of the different parts of plants Teacher Resources Teacher Resource 1.2 FRUIT/ SEEDPOD Holds seeds for new

The important roles of the different parts of plants

Teacher ResourcesTeacher Resource 1.2

FRUIT/SEEDPOD

Holds seeds for

new plants.

LEAVES

Catch light to make food

helping the plant grow.

ROOTS

Take water and nutrients

out of the soil. (This

could also be a bulb,

corm etc.).

STEM

Holds the plant

up; carries water

and nutrients to

the leaves.

FLOWERS

Make the fruit and

seeds so the plant can

reproduce.

Ghastly Guests • Upper primary unit of work investigating weeds • Cooperative Research Centre for Australian Weed Management 51

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4a

Ghastly Guests • Upper primary unit of work investigating weeds • Cooperative Research Centre for Australian Weed Management

Suggested answers

1.4a Mimosa pigra

Q1 Where did Mimosa pigra originate from before it was introduced into Australia?

Mimosa pigra was introduced into Australia from Central and South America.

Q2 Where in Australia could Mimosa pigra potentially be found?

Mimosa pigra could potentially be found in northern Australia, from WA to Qld. Kakadu National Park NT

spends half a million dollars each year to keep it out.

Q3 In favourable conditions how much could Mimosa pigra grow in one day?

In favourable conditions Mimosa pigra could grow 1cm in one day.

Q4 Why do some introduced plants and animals become problems?

Plants and animals which are introduced into another area may not have natural predators in this new

environment. As a result their population may not be controlled and they can become weeds and pests.

Q5 This plant has special features to stop animals eating it and reacts when touched. Explain these

features and the reaction of Mimosa pigra.

Mimosa pigra has thorns which stop animals eating it and its leaves move together as if to close when

touched. It is also called giant sensitive plant.

Q6 List all the adjectives used in this passage to describe Mimosa pigra.

The adjectives used in this passage to describe Mimosa pigra are: horrid; thorny; fast growing; sly; cunning;

lazy; slothful; sneaky; deceiving; and scheming.

Q7 Using the list of words you have written down for Q6, explain how the writer of this passage has

made you feel about Mimosa pigra.

Discuss with students.

Q8 Discuss the characteristics which you feel make Mimosa pigra a weed.


Characteristics making Mimosa pigra a weed are:

mimosa can’t be eaten by grazing animals due to its thorns;

mimosa is introduced and has no natural predators in Australia; and

mimosa grows at such a fast rate that it tends to cover large areas quickly.

Teacher ResourcesTeacher Resource 1.4a continued

St

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Suggested answers

1.4b St John’s wort

Q1 How many seeds (approximately) is one St John’s wort plant capable of producing each year?

One St John’s Wort plant is capable of producing up to 33 000 seeds each year.

Q2 There are two reasons the seeds produced by this weed help it spread into new areas. One is the

huge number of seeds. What is another characteristic of the seeds that helps this plant spread?

The St John wort plant has very sticky seeds. These sticky seeds catch onto moving objects and this helps

the plant spread into new areas.

Q3 Are there any good qualities of this weed?

This weed has medicinal properties and is used as an antidepressant.

Q4 At what stage of the plant’s lifecycle is the worst time to let animals eat the plant?

The worst time to let animals eat the plant is when the plant is flowering or producing seed.

Q5 Affected animals must be removed from the group and held in a shady area for at least a week.

Why do you think this is the best method of treating sick animals?

Affected animals are very susceptible to sunlight and should be removed from the group and held in a shady

area to reduce any further exposure.

Q6 One method of controlling the weed is to let merino sheep graze the plant when it is young and not

flowering. Then spray with herbicide when the plant has flowers. Describe why you think this would

or may not work.

Allowing merino sheep to graze the plant when it is young and not flowering is helpful in managing the plant,

as merino sheep are the least susceptible to the plant’s toxins and the plant should not be eaten when flowering.

Q7 How has the writer of this passage made you feel about St John’s wort?


Q8 Discuss how this passage is written to persuade you to dislike the St John’s wort weed.

Discuss with students. In particular investigate the adjectives the writer has used to describe St John’s wort

and the use of the wicked witch as a simile of the weed.

Teacher ResourcesTeacher Resource 1.4b continued

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4c

Bri

dal

cree

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Suggested answers

1.4c Bridal creeper

Q1 How is bridal creeper commonly used?

Bridal creeper is commonly used in floral arrangements, especially bridal bouquets.

Q2 Bridal creeper was introduced into Australia from what country?

Bridal creeper was introduced into Australia from South Africa.

Q3 The seeds of bridal creeper can be transported into new areas when birds eat the fruit.

Explain another way birds disperse the plant’s seeds.

The sticky seed will attach to bird’s beaks and will be taken with the birds into new areas.

Q4 What is a ‘garden escape’ and what are some things we can do to avoid ‘garden escapes’?

A garden escape is a plant which spreads beyond the garden and becomes weedy. Things we can do to avoid

garden escapes include: keeping plants within our garden boundaries, avoiding careless dumping of garden

wastes and planting local native plants in our gardens.

Q5 What are four features of bridal creeper, mentioned in the passage, making it a weed?

• Birds are attracted to bridal creeper’s sticky berries and transport the seeds into new areas.

• Bridal creeper forms a mat of tubers. The tubers help it to grow and limit the growth of other plants.

• Bridal creeper seeds germinate faster than other plants.

• Bridal creeper climbs up and over other plants, forming a canopy and smothering plants even 2–3m high.

Q6 Why is it suggested not to introduce plants into a new area?

Plants introduced into a new area, without their natural enemies, sometimes grow uncontrollably and can

become weeds.

Q7 What is the message the writer of this passage is giving about the way we should do our gardening?

The writer is persuading the reader to think about how to be a smart gardener. This means avoiding allowing

plants in our gardens to become garden escapes/weeds.

Q8 Discuss additional things gardeners can do to be smart gardeners.

Discuss with students. While students may have additional suggestions, here are some ideas.

• disposing of weeds and garden wastes by composting, or placing in a garbage bag and disposing appropriately.

• maintain gardens so new weeds are obvious and can be removed at the right time.

• avoid introducing plants into new areas and encourage other gardeners to do the same.

Teacher ResourcesTeacher Resource 1.4c continued

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4d

Lant

ana


Suggested answers

1.4d Lantana

Q1 From what area is lantana native?

Lantana is native to Central America.

Q2 How much land in Australia is occupied by lantana?

In Australia 4 million ha is occupied by lantana.

Q3 How many seeds can a mature lantana plant produce?

A mature lantana plant is capable of producing up to 12 000 seeds per year.

Q4 Use the 3 dates provided to develop a timeline to display the introduction, spread and current

distribution of lantana.

Q5 What two ways mentioned in this passage, describe how lantana is able to spread into new areas?

The two main ways lantana spreads into new areas is through layering and animals transporting seeds.

Q6 Which features described in this passage explain why lantana is a weed?

• Lantana has spread rapidly becoming a weed along the east coast of Australia.

• Lantana is able to form dense thickets by layering.

• Lantana is able to produce a high number of seeds.

• Lantana can be toxic to animals.

• Lantana is allelopathic.

Q7 State two pieces of evidence that indicate lantana is not likely to spread into the more arid

central Australia?

1. The map of Australia showing the current distribution and the potential distribution indicates that lantana

will not spread into the centre of Australia.

2. The information in the passages explains that lantana will grow in high rainfall areas with tropical and

subtropical climates. This is not the case for the drier centre of Australia.

Q8 Discuss the reasons you think lantana was originally introduced into Australia and so many

other countries.

Discuss with students. Lantana was introduced into many countries as an ornamental plant. Lantana is an

attractive plant and for this reason it has been planted in many gardens.

Teacher ResourcesTeacher Resource 1.4d continued

1843 1850s Currently in 2006

Lantana introduced and grown Lantana established along Lantana is found along the east coast

in Australia at Camden Park the Brisbane River of Australia from Sydney in New South

in New South Wales. in Queensland. Wales, to Cairns in Queensland. Also in

isolated areas in Northern Territory

and Western Australia.

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4e


Suggested answers

1.4e Gorse

Q1 Gorse is a native to what area?

Gorse is a native of Europe and the United Kingdom.

Q2 Where in Australia is this plant currently found?

Gorse is currently found in all states and territories of Australia except the Northern Territory.

Q3 How many seeds per hectare is a mature infestation of gorse capable of producing?

A mature infestation of gorse is capable of producing six million (6 000 000) seeds per hectare.

Q4 For what purpose was gorse initially introduced into Australia and New Zealand?

Gorse was initially introduced into both Australia and New Zealand to be grown as a hedge.

Q5 Describe the facts included in this passage that indicate that this plant has become a serious problem

in New Zealand and Australia.

• Since its introduction into Australia, gorse has become established in all states and territories except the

Northern Territory.

• When gorse was first introduced into New Zealand, a condition of rental of crown land was that you had

to plant gorse as a hedge. After the plant became a serious weed, anyone who continued to plant gorse

was fined.

Q6 What are the features described in this passage, which explain why gorse is a weed?

• This plant is able to invade ecosystems with ease and control is difficult and expensive.

• The plant provides a home to other pests (especially rabbits).

• The plant is highly flammable and increases the risk of bush fires.

• The plant forms dense thickets, is capable of growing up to three meters high and has sharp spines limiting access.

• The plant has an extensive root system, which works to take resources from other plants.

• The plant produces seeds which are capable of remaining dormant for up to30 years.

Q7 Gorse seeds can remain dormant in the soil for up to 30 years. Explain why you think this

becomes a problem.

Weed seeds that remain in the soil are called the ‘weed seed bank’. These seeds are waiting to germinate

when conditions become favourable. Weed seeds that are dormant in the soil are long term problems, which

can germinate many years later. Because the problem is hidden in the soil, they are an unknown quantity and

can be nasty surprises.

Q8 Discuss the reason why plants which are introduced into a new area without their natural

enemies/predators often become weeds.

Discuss with students. Without their natural enemies or predators, plants introduced into new areas often

grow uncontrollably.

Teacher ResourcesTeacher Resource 1.4e continued

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Teacher ResourcesTeacher Resource 2.6

Activities causing weed spread

Documents

The important roles of the different parts of plants...The important roles of the different parts of plants Teacher Resources Teacher Resource 1.2 FRUIT/ SEEDPOD Holds seeds for new