Plant Diseases and Defences
This lesson covers:
- How to tell when a plant has a disease
- The defences that plants have to help prevent disease
The three main causes of plant diseases:
- Infection by microorganisms such as fungi, , or viruses.
- Attack by larger organisms, such as insects.
- Lack of essential , such as nitrates, or magnesium ions.
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What is the primary mode of transmission for tobacco mosaic virus (TMV)?
Spores from the soil
Airborne spores
Seed transmission
Direct contact with infected plants
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What is a common symptom of barley powdery mildew infection?
Yellow mosaic patterns on leaves
Tumour-like growths on stems
Root galls
Powdery spots on leaves
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How does the pathogen that causes crown gall disease enter the plant?
Through the roots during water uptake
Through stomata on the leaves
Through wounds on the plant
Through the vascular system
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Why do plants require nitrates?
To make carbohydrates
To make chlorophyll
To make proteins
To make lipids
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Which of the following is a symptom of nitrate deficiency (lack of nitrates) in a plant?
Chlorosis (yellow leaves due to lack of chlorophyll)
Stunted growth
Brown spots on the leaves
Small holes in the leaves
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Why do plants require magnesium?
To make lipids
To make proteins
To make carbohydrates
To make chlorophyll
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What is the main symptom of magnesium deficiency (lack of magnesium) for a plant?
Chlorosis (yellow leaves due to lack of chlorophyll)
Brown spots on the leaves
Small holes in the leaves
Purple leaves
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List three physical changes that could indicate that a plant has a disease.
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Give three ways in which plant diseases can be identified.
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Plants have many defences against pathogens. What do we mean by physical defences?
Defences that physically prevent the entry of pathogens
Chemicals that plants can secrete to destroy pathogens
Structures that reduce the chance of being attacked
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Which of the following plant defences are considered physical defences?
(Select all that apply)
Thorns and hairs
A waxy cuticle on the leaves and stems
Strong cellulose cell walls
Production of antimicrobial substances
Layers of dead cells around the trunk (bark)
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Plants have many defences against pathogens. What do we mean by chemical defences?
Defences that physically prevent the entry of pathogens
Structures that reduce the chance of being attacked
Chemicals that plants can secrete to destroy pathogens
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Which of the following plant defences are considered chemical defences?
(Select all that apply)
Production of antimicrobial substances
Production of poisons that kill insects
Layers of dead cells around the trunk (bark)
Mimicking other organisms to trick animals
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Plants have many defences against pathogens. What do we mean by mechanical defences?
Defences that physically prevent the entry of pathogens
Chemicals that plants can secrete to destroy pathogens
Structures that reduce the chance of being attacked
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Which of the following plant defences are considered mechanical defences?
(Select all that apply)
Production of antimicrobial substances
Hairs and thorns
Leave that curl or droop when insects land on them
Mimicking other organisms to trick animals
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