1. What type of pathogen causes tobacco mosaic virus (TMV) and rose black spot ?
Answer
TMV is caused by a virus, while rose black spot is caused by a fungus.
2. Name the types of insect pests that can affect plants.
Answer
Aphids, spider mites, white flies, etc.
3. Which ions are needed for protein synthesis and the production of chlorophyll ?
Answer
Nitrate is essential for protein synthesis, whereas magnesium is required for chlorophyll production.
4. Give some ways that plant disease can be detected.
Answer
Stunted growth, spots on leaves, areas of decay (rot), growths on stems or leaves, malformed stems or leaves, discolouration e.g. yellow leaves (chlorosis) or presence of pests.
5. Describe three ways that a gardener could identify a plant disease.
Answer
Plant diseases can be identified by referring to a gardening manual or website, taking infected plants to a laboratory to identify the pathogen or using testing kits that contain monoclonal antibodies.
6. Why does a gardener need to know about ion deficiencies ?
Answer
So he can provide the optimum conditions for plants to grow.
7. Describe the appearance of a plant with nitrate ion deficiency.
Answer
A plant with a nitrate ion deficiency exhibits stunted growth.
8. Plants deficient in magnesium ions may have poor growth. Explain why.
Answer
Plants with a magnesium ion deficiency develop yellow leaves (chlorosis). They produce less chlorophyll and therefore absorb less light. This reduces the rate of photosynthesis, resulting in lower glucose production. Less glucose means reduced protein synthesis, leading to less growth; it also means less respiration, resulting in less energy for growth; and less glucose means less cellulose for building new cell walls, which also limits growth.
9. Describe three physical defence responses that plants have to resist the invasion of microorganisms.
Answer
Cellulose cell walls are tough and act as a barrier that microorganisms find difficult to penetrate. Leaves have a waxy cuticle that is tough and difficult for microorganisms to penetrate. A layer of dead cells around stems or the bark on trees falls off taking pathogens with them.
10. Describe two chemical defence responses that plants use against other organisms.
Answer
Some plants produce antibacterial chemicals that kill bacteria or inhibit their growth. Some plants produce poisons to deter herbivores.
11. Suggest why it is an advantage for a plant to have leaves that droop or curl when they are touched.
Answer
So that small animals like insects will fall off.
12. Female butterflies are less likely to lay their eggs on plants that already have butterfly eggs. The leaves of a flowering plant have yellow spots on them by default. Suggest why these spots might be an advantage for the plant.
Answer
The yellow spots make it look like the leaves already have eggs on them, so the butterfly does not lay eggs on the leaves and they are not eaten (or damaged) by caterpillars.
13. Some plants have thorns on their stems or stinging hairs on their stems and leaves. Explain how the prickles help the plant to survive.
Answer
Prickles can cause pain, deterring animals and herbivores from feeding on the leaves, fruit, or the plant itself.