Two plant varieties have similar cell walls but different cuticle thicknesses. Variety P has fewer infections than variety Q when spores are placed on intact leaves. Both have similar infection rates when spores are placed through small punctures.
Which conclusion best explains both results?
a difference in the cell walls must account for the resistance of P
P must produce a chemical that kills every spore after it enters a leaf
Q must lack living cells that can be infected through an intact surface
a difference in the surface barrier could account for the resistance of P
45 exam-style questions on Edexcel GCSE Biology 5.2 Plant and body defences, covering 5.2.1 Physical plant defences, 5.2.2 Chemical plant defences, 5.2.3 Detecting plant diseases, and 5.2.4 Human physical and chemical defences. Each one has a worked solution and a mark scheme showing where the marks go.