AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
(HT only) Plant diseases can be detected by: • stunted growth • spots on…
Full specification wording
Detection and identification of plant diseases: (HT only) Plant diseases can be detected by: • stunted growth • spots on leaves • areas of decay (rot) • growths • malformed stems or leaves • discolouration • the presence of pests.
Plants show visible signs when they are diseased, and gardeners and scientists use these signs to detect a problem before identifying the cause.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Plants show visible signs when they are diseased, and gardeners and scientists use these signs to detect a problem before identifying the cause. Stunted growth means the plant is smaller than expected for its age and conditions. Spots on leaves may be discoloured patches caused by a pathogen. Areas of decay or rot are soft, broken-down tissue, often on fruit, roots or stems. Growths are abnormal lumps, such as crown galls. Malformed stems or leaves are twisted or misshapen. Discolouration is a change in the normal colour, such as yellowing. The presence of pests, such as insects on the plant, is itself a sign to look for. These signs indicate disease but do not by themselves identify the pathogen.
What earns the marks
- Stunted growth is when a plant is smaller than expected for its age and growing conditions.
- Spots on leaves are discoloured patches that can indicate infection by a pathogen.
- Areas of decay or rot are regions of soft, broken-down plant tissue.
- Growths are abnormal lumps on the plant, and malformed stems or leaves are twisted or misshapen.
- Discolouration is a change from the normal colour, such as yellowing of leaves.
- The presence of pests, such as insects, is a visible sign that can be recorded when detecting disease.
Common mistakes and how to put them right
Treating a visible sign as proof of a named pathogen.
Put it right: The sign shows disease is present, and further identification is needed to name the cause.
Confusing stunted growth with malformed growth.
Put it right: Stunted means smaller than expected, while malformed means misshapen.
Forgetting that pests count as a detectable sign.
Put it right: The presence of pests is included in the list of signs to look for.
Exam tips
- Learn the seven signs as a list and be ready to match each to a description.
- When asked to detect disease, name the sign you observe before suggesting a cause.
- Use precise wording such as stunted growth, discolouration and areas of decay.
Try the lesson
The start of the Detection and identification of plant diseases: (HT only) Plant diseases can be detected by: • stunted growth • spots on leaves • areas of decay (rot) • growths • malformed stems or leaves • discolouration • the presence of pests. lesson, made from checked teaching notes for this specification point.
Have a go first
A gardener notices that a tomato plant is much shorter than the others and its leaves have yellow patches. Which two signs of plant disease are shown?
Listen
Plants show visible signs when they are diseased, and gardeners and scientists use these signs to detect a problem before identifying the cause. Stunted growth means the plant is smaller than expected for its age and conditions. Spots on leaves may be discoloured patches caused by a pathogen. Areas of decay or rot are soft, broken-down tissue, often on fruit, roots or stems. Growths are abnormal lumps, such as crown galls. Malformed stems or leaves are twisted or misshapen. Discolouration is a change in the normal colour, such as yellowing. The presence of pests, such as insects on the plant, is itself a sign to look for. These signs indicate disease but do not by themselves identify the pathogen. A strong answer earns marks for these points. Stunted growth is when a plant is smaller than expected for its age and growing conditions. Spots on leaves are discoloured patches that can indicate infection by a pathogen. Areas of decay or rot are regions of soft, broken-down plant tissue. Growths are abnormal lumps on the plant, and malformed stems or leaves are twisted or misshapen. Exam tip: Learn the seven signs as a list and be ready to match each to a description.
Key words
Say what each word means before you turn the card.
Stunted growth
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Areas of decay
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Discolouration
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Detection of plant disease from visible signs
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See every definition
- Stunted growth
- When a plant is smaller than expected for its age and growing conditions.
- Areas of decay
- Regions of soft, broken-down plant tissue, often on fruit, roots or stems.
- Discolouration
- A change from the normal colour, such as yellowing of leaves.
- Detection of plant disease from visible signs
- Using visible signs to detect a problem before identifying the cause; these signs indicate disease but do not by themselves identify the pathogen.
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