Fungal diseases — AQA GCSE Biology
Test yourself on Fungal diseases with AQA GCSE practice questions.
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Fungal diseases explained
Rose black spot damages leaves, and leaves are the main organs of photosynthesis.
Read the full explanation
The fungus destroys areas of leaf tissue and causes yellowing, which reduces the amount of chlorophyll available to absorb light. When infected leaves drop early, the plant has fewer leaves and a smaller total leaf area. Less chlorophyll and fewer leaves mean less light energy is absorbed, so the rate of photosynthesis falls. Photosynthesis produces glucose, which the plant uses for respiration, growth and making new cells. With less glucose, the plant's growth is reduced. A concrete example is a rose bush that loses many leaves in summer; it produces fewer new shoots and smaller flowers because it cannot make enough glucose for growth.
Your focus
- Explain how leaf damage reduces photosynthesis.
- Relate reduced photosynthesis to reduced glucose and slower growth.
- Describe the chain from fungal infection to stunted plant growth.
Fungal diseases exam tips
Marking Points
- Rose black spot damages leaf tissue and reduces chlorophyll.
- Yellowing and early leaf drop reduce the total leaf area available for photosynthesis.
- Less chlorophyll and fewer leaves mean less light energy is absorbed.
- A lower rate of photosynthesis means less glucose is produced.
- Reduced glucose availability limits the plant's growth.
Examiner Tips
- 💡Link leaf damage to reduced chlorophyll and reduced light absorption.
- 💡Explain the consequence: less glucose means less growth.
- 💡Use the term 'rate of photosynthesis' when describing the effect.
Common Mistakes
- Saying the plant cannot respire at all; the correction is that photosynthesis is reduced, which lowers glucose production and therefore growth.
- Thinking the fungus directly eats the plant's roots; the correction is that it affects leaves, reducing photosynthesis.
- Confusing reduced photosynthesis with reduced transpiration; the correction is that the statement is about photosynthesis and glucose production for growth.