1.1. Higher Tier Only

Plants can be infected by a range of pathogens.

Aphids are small insects that feed on plant sugars and carry pathogens.

Figure 1 shows part of a plant infested with aphids.

Figure 1

Plants infested with aphids show signs of reduced growth.

Suggest and explain one reason why.

1.2. Higher Tier Only

It is common for plants infested with aphids to show signs of magnesium deficiency.

Describe and explain the symptoms displayed by a plant with a magnesium deficiency.

1.3. Plants have methods of protecting themselves from attack. One such method is the production of oils by cells on the surface of leaves. 

Suggest two ways that the production of oils might protect a plant from being attacked by herbivores, including herbivorous insects. 

1.4. Higher Tier Only

A number of plants in a garden are infected with a pathogen.

Give two ways of identifying the pathogen that is infecting the plants in the garden.