Plant disease and defences

What are the three ways a plant can get a disease

micro-organism, organism, mineral deficiencies

What are the two most common types of mineral deficiencies

1) Nitrate - responsible for making proteins, a lack of means stunted growth

2) Magnesium ions - responsible for production chlorophyll, needed for respiration. Lack of creates yellow leaves and chlorosis

What are four common symptoms of a diseased plant and what can you sometimes see

1) Discolouration

2) Lymph or node

3) Malformed stem/leaves

4) Plant decay

You can sometimes see the organism that is causing the disease (if it is the cause), e.g. aphids or spider mites

What are three common methods of diagnosing a plant

1) Compare to a gardening manual

2) Trial and error

3) Send to a plant pathologist

More detail on sending samples to plant pathologists (3 things they do)

Plant pathologists can give a much more detailed reading of a plant. They:

1) use microscopes to better understand problems

2) do DNA tests on the plant to try and find if there is any pathogen DNA present

3) test for specific antibodies (from pathogens) using monoclonal antibodies

What are the three types of plant defences

1) physical

2) chemical

3) mechanical

Define and give three examples of physical defences

Physically preventing pathogens from entering the plant cells:

1) Dead cells build up (bark)

2) Cellulose cell wall

3) Waxy cuticles on leaves

Define and give two examples of chemical defences

Chemicals the plant produces

1) Secreting anti-microbials that can kill pathogens or fungi

2) Poisons that kill insects if they try to eat the plant, so that they don’t

Define and give two examples of mechanical defences

Purposes rather than functions

1) Thorns and hairs prevent animals from eating the plant

2) Leaves that droop when insects land on it to prevent them staying