A woodland shrub normally produces a chemical in cells around damaged parts of its stems. A researcher applies a treatment that prevents some shrubs from producing this chemical. The treatment has no other effect on the shrubs. The same number of bacteria is placed onto a cut in the stem of each shrub.
Explain why the treated shrubs are more likely to develop a bacterial disease than untreated shrubs.
133 exam-style questions on AQA GCSE Biology 3.3 Plant disease, covering 3.3.1 Detection and identification of plant diseases and 3.3.2 Plant defence responses. Each one has a worked solution and a mark scheme showing where the marks go.