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Edexcel Biology Gcse > plant diseases > Flashcards

Flashcards in plant diseases Deck (34)
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1
Q

What are antibacterial chemicals?

A

Naturally occurring chemicals made by plants like mint and witch hazel which protect them from bacterial pathogens

2
Q

bacteria

definition

A

Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium

3
Q

biodiversity

meaning

A

The range of animals and plants in a given area

4
Q

cellulose

definition

A

A carbohydrate. It forms the cell wall in plant cells.

5
Q

communicable disease

definition

A

A disease that is caused by a pathogen and so is transmitted rather than inherited or caused by an environmental factor.

6
Q

cuticle

definition

A

The outer layer of a leaf which protects it.

7
Q

fungi

definition

A

A large group of eukaryotic organisms that contain single celled yeasts, moulds and mushrooms.

8
Q

genetic engineering

definition

A

Process which involves the artificial transfer of genetic information from one donor cell or organism to another.

9
Q

herbivore

definition

A

An animal that feeds only on plants

10
Q

host

definiton

A

The organism lived on or in by a parasite.

11
Q
pathogen
definition (basic)
A

Microorganism that causes disease.

12
Q

protist

definition

A

A eukaryotic, usually single-celled organism of the kingdom Protista.

13
Q

transmission

meaning

A

The spreading of pathogenic disease, for example by touch, food, water.

14
Q

What are viruses?

A

Ultramicroscopic non-cellular organisms that replicate themselves inside the cells of living hosts.

15
Q
Pathogen
definition (detailed)
A

A pathogen is an organism that causes a disease. There are four main types of pathogen: viruses, bacteria, fungi, and protists. All types of pathogen have a simple life cycle. They infect a host, reproduce (or replicate themselves if a virus), spread from their host and then infect other organisms.

16
Q

What are the 4 main types of pathogen?

A
  • Viruses
  • Bacteria
  • Fungi
  • Protists
17
Q

Effects of plant pathogens

A

Plant pathogens kill or reduce the growth of many plants, which in turn can reduce biodiversity.

18
Q

Identification of pathogens
Scientists want to identify potential plant pathogens as quickly as possible to reduce the likelihood of an infection spreading. The process to identify a disease may include the following steps:

A

1) Following a report of a possible infection, scientists will visit the location.
2) To avoid any confusion it is essential they look at other factors that might cause similar symptoms. For example, damage to leaves might be caused by a pathogen or grazing animals.
3) The scientists will try to identify any environmental causes such as pollution that might be affecting the plants.
4) Finally they will photograph the symptoms and take samples for laboratory analysis.

19
Q

Identification of pathogens
Scientists want to identify potential plant pathogens as quickly as possible to reduce the likelihood of an infection spreading.

What is the next step after identifying the infection?

A

Once an infection has been identified, scientists will look for any patterns in the distribution of infected plants. Do they all appear downwind of the first infection? Are future cases reported along the banks of rivers and streams?

20
Q

Identification of pathogens

Symptoms of plant disease

A

Plant pathogens cause diseases with a range of different symptoms. These symptoms can be used to identify the pathogen and then treat the disease, or limit its effects.

Pests can also cause damage to plants. Examples are the insects, aphids and mealybugs. Although these do not cause disease, as pathogens do, they can weaken and damage the plant. It is important to identify which pests are causing symptoms, as well as identifying which pathogen is causing a disease, so that the correct treatment can be decided.

21
Q

Identification of pathogens
Symptoms of plant disease
Give 6 examples of symptoms of common plant infection.

A
  • Stunted growth from mealybugs: Mealybugs can cause dehydrated plants which are likely to have stunted growth
  • (Black and purple) Spots on leaves caused by the rose black spot fungus
  • Decay caused by the rice blast fungus
  • Malformed stems or leaves caused by the ash dieback fungus
  • Discoloration caused by the tobacco mosaic virus
  • The presence of pests (aphids): Aphid insects suck sap from a nettle
22
Q

Identification of pathogens

A

Farmers and gardeners often use books like gardening manuals and the internet to identify plant diseases. They do this by comparing the symptoms of their plants with images of other infected ones. Gardeners can also take a small cutting of an infected plant (or a photograph of it) to a local garden centre. Here staff can help identify the disease by looking at its symptoms. Gardeners can then buy suitable treatments from the garden centre to treat the disease.

23
Q
Plant defences
(overview)
A

Plants are constantly defending themselves from attack from pests and pathogens. Like animals, plants have physical and chemical defences which help to prevent infection and disease.

24
Q

Plant defences

List Physical defences

A
  • Bark
  • Thorns and hairs
  • Drooping leaves
25
Q

Plant defences
Physical defences

Bark

A

Many plants are covered with a thick bark. This is an external layer of dead cells which forms a physical barrier against infection. In this way it is very much like our skin. Leaves are covered with waxy cuticle which also helps to prevent their cells from becoming infected

Beyond bark and the waxy cuticle, each plant cell has a cellulose cell wall which acts as another barrier against infection. Some pathogens overcome this barrier by releasing enzymes that soften the cell wall.

26
Q

Plant defences
Physical defences

Thorns and hairs

A

Plants like roses have evolved large thorns to avoid being eaten, while plants like cacti have evolved thin spines. These adaptations protect plants from damage from pests and from disease from pathogens carried by pests.

27
Q

Plant defences
Physical defences

Drooping leaves

A

The Mimosa pudica plant is very special. It has evolved to close its leaves and then point its stems towards the ground when touched by an insect as it lands on it. This movement is a defence mechanism which acts to dislodge any insect that rests on it. You can see this happen below.

28
Q

Plant defences
Chemical defences

Why, as opposed to physical?

A

Sometimes physical defences are not enough to protect a plant. Physical barriers alone will often not be enough of a deterrent against plant eating pests for example.

29
Q

Plant defences
Chemical defences

poisons

A

Some plants, like stinging nettles and foxgloves, have developed poisons to deter herbivores from eating them. They produce these constantly. These do not defend plants from infection by pathogens.

30
Q

Plant defences
Chemical defences

Toxins

A

Other plants produce toxins in response to being attacked, for example, some plants release a toxin into the air when attacked by aphids. This toxin acts as a warning to other aphids, causing them to fly away.

31
Q

Plant defences
Chemical defences

antibacterial chemicals

A

As a way of defending themselves against pathogens, some plants such as mint and witch hazel produce antibacterial chemicals. These kill bacteria that were not stopped by physical defences. We now use these chemical defences in antiseptics for humans.

32
Q

Plant defences

Defences other than physical and chemical

A

Farmers can now genetically engineer crop plants to be resistant to infections.

33
Q

Plant defences

What type of pathogen is Chalara ash dieback?

A

Fungus

34
Q

Plant defences

What plants are aphids often found on?

A

Roses