plant diseases Flashcards
bbc bitesize
What are antibacterial chemicals?
Naturally occurring chemicals made by plants like mint and witch hazel which protect them from bacterial pathogens
bacteria
definition
Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium
biodiversity
meaning
The range of animals and plants in a given area
cellulose
definition
A carbohydrate. It forms the cell wall in plant cells.
communicable disease
definition
A disease that is caused by a pathogen and so is transmitted rather than inherited or caused by an environmental factor.
cuticle
definition
The outer layer of a leaf which protects it.
fungi
definition
A large group of eukaryotic organisms that contain single celled yeasts, moulds and mushrooms.
genetic engineering
definition
Process which involves the artificial transfer of genetic information from one donor cell or organism to another.
herbivore
definition
An animal that feeds only on plants
host
definiton
The organism lived on or in by a parasite.
pathogen definition (basic)
Microorganism that causes disease.
protist
definition
A eukaryotic, usually single-celled organism of the kingdom Protista.
transmission
meaning
The spreading of pathogenic disease, for example by touch, food, water.
What are viruses?
Ultramicroscopic non-cellular organisms that replicate themselves inside the cells of living hosts.
Pathogen definition (detailed)
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.
What are the 4 main types of pathogen?
- Viruses
- Bacteria
- Fungi
- Protists
Effects of plant pathogens
Plant pathogens kill or reduce the growth of many plants, which in turn can reduce biodiversity.
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:
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.
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?
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?
Identification of pathogens
Symptoms of plant disease
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.
Identification of pathogens
Symptoms of plant disease
Give 6 examples of symptoms of common plant infection.
- 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
Identification of pathogens
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.
Plant defences (overview)
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.
Plant defences
List Physical defences
- Bark
- Thorns and hairs
- Drooping leaves
