Plant Diseases & 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.
|
What is the primary mode of transmission for tobacco mosaic virus (TMV)?
Direct contact with infected plants
Airborne spores
Spores from the soil
Seed transmission
|
Why do plants require nitrates?
To make chlorophyll
To make lipids
To make carbohydrates
To make proteins
|
Which of the following is a symptom of nitrate deficiency (lack of nitrates) in a plant?
Stunted growth
Brown spots on the leaves
Chlorosis (yellow leaves due to lack of chlorophyll)
Small holes in the leaves
|
Why do plants require magnesium?
To make proteins
To make carbohydrates
To make chlorophyll
To make lipids
|
What is the main symptom of magnesium deficiency (lack of magnesium) for a plant?
Purple leaves
Small holes in the leaves
Chlorosis (yellow leaves due to lack of chlorophyll)
Brown spots on the leaves
|
List three physical changes that could indicate that a plant has a disease.
|
Give three ways in which plant diseases can be identified.
|
Plants have many defences against pathogens. What do we mean by physical defences?
Chemicals that plants can secrete to destroy pathogens
Structures that reduce the chance of being attacked
Defences that physically prevent the entry of pathogens
|
Which of the following plant defences are considered physical defences?
(Select all that apply)
Layers of dead cells around the trunk (bark)
Thorns and hairs
Production of antimicrobial substances
A waxy cuticle on the leaves and stems
Strong cellulose cell walls
|
Plants have many defences against pathogens. What do we mean by chemical defences?
Chemicals that plants can secrete to destroy pathogens
Structures that reduce the chance of being attacked
Defences that physically prevent the entry of pathogens
|
Which of the following plant defences are considered chemical defences?
(Select all that apply)
Layers of dead cells around the trunk (bark)
Mimicking other organisms to trick animals
Production of poisons that kill insects
Production of antimicrobial substances
|
Plants have many defences against pathogens. What do we mean by mechanical 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
|
Which of the following plant defences are considered mechanical defences?
(Select all that apply)
Mimicking other organisms to trick animals
Production of antimicrobial substances
Leave that curl or droop when insects land on them
Hairs and thorns
|