Identify and describe Causes of Plant Disease, Recognising Symptoms of Plant Disease and Diagnosing Plant Disease: Basic Methods in the context of plant tissues.
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GCSE Biology Revision
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GCSE Biology revision
Plant tissues
Plant tissues, organs and systems
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Explain the relationships between Causes of Plant Disease, Recognising Symptoms of Plant Disease and Diagnosing Plant Disease: Basic Methods and how they contribute to plant tissues.
Apply and analyse knowledge of Causes of Plant Disease, Recognising Symptoms of Plant Disease and Diagnosing Plant Disease: Basic Methods to interpret unfamiliar information about plant tissues.
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Causes of Plant Disease
- Plants can catch diseases from a range of microorganisms, including fungi, bacteria, and viruses, as well as larger organisms such as insects
- Plants can also suffer from deficiency diseases if they do not receive sufficient essential minerals from the soil
- A lack of nitrates, which are needed for protein synthesis, leads to stunted growth in plants
- A deficiency in magnesium ions, which are required to produce chlorophyll, causes chlorosis, resulting in yellow leaves
Recognising Symptoms of Plant Disease
- Common symptoms of plant disease include abnormal growths or lumps, malformed stems or leaves, and patches of decay
- Spots of discolouration on leaves are another key indicator that a plant may be suffering from a disease
- In some cases, the organism responsible for the disease, such as aphids or spider mites, may be visible to the naked eye
Diagnosing Plant Disease: Basic Methods
- The simplest diagnostic method is to observe symptoms and match them to a known disease using a garden manual or a reliable website
- A trial-and-error approach can also be used, for example applying magnesium supplements to a plant suspected of having a magnesium deficiency to see if symptoms improve
- If a suspected fungal infection is present, spraying the plant with anti-fungal chemicals and monitoring the response is a practical trial-and-error technique
Diagnosing Plant Disease: Advanced Methods
- A sample of the diseased plant can be sent to a plant pathologist, a specialist in plant disease, for more detailed analysis
- Plant pathologists can examine tissue samples under a microscope to identify problems at a cellular level
- Unique antigens produced by specific pathogens can be detected using monoclonal antibodies, providing a more precise diagnosis
- DNA testing can be carried out to identify pathogen DNA within the plant, offering the most accurate form of diagnosis
Physical and Chemical Plant Defences
- Physical defences actively prevent the entry of pathogens and include the waxy cuticle that covers the leaves and stems of many plants
- Cell walls surrounding each individual plant cell provide a structural barrier against pathogen invasion
- Some plants have layers of dead cells, such as bark, around their stems, which act as an additional physical barrier
- Chemical defences involve the secretion of antimicrobial substances that kill bacteria or fungi, or poisons that deter or kill insects
Mechanical Plant Defences
- Mechanical defences are similar to physical defences but serve an active function beyond simply acting as a barrier
- Thorns and hairs on plant surfaces deter animals from eating or touching the plant
- Some plants have leaves that curl or droop when insects land on them, helping to dislodge or discourage pests
Plants as a Source of Medicines
- Plants produce a vast array of chemicals, many of which form the basis of important medicines used by humans
- Aspirin, a widely used painkiller, is derived from chemicals found in the bark and leaves of willow trees