Detecting and identifying plant disease, ion deficiencies, and the physical, chemical and mechanical defences plants use. Biology only content.
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1.Give five signs that a plant may be diseased.
Stunted growth, spots on the leaves, areas of decay, growths, malformed stems or leaves, and discolouration.
2.Give three ways a plant disease can be identified.
Using a gardening manual or website, taking the plant to a laboratory to identify the pathogen, or using testing kits containing monoclonal antibodies.
3.What causes a nitrate deficiency in a plant, and what is the effect?
Not enough nitrate ions in the soil. Nitrates are needed to make proteins, so the plant shows stunted growth.
4.What is the effect of magnesium deficiency?
Magnesium is needed to make chlorophyll, so the leaves turn yellow. This is called chlorosis.
5.Why does chlorosis reduce plant growth?
Without enough chlorophyll the plant cannot photosynthesise properly, so it makes less glucose.
6.Name three physical defences plants use.
A waxy cuticle, layers of dead cells around stems such as bark, and cellulose cell walls.
7.How does the waxy cuticle act as a defence?
It forms a barrier that pathogens cannot easily get through.
8.How does bark defend a tree?
The dead cells fall off, taking any pathogens on them away with them.
9.Name two chemical defences plants use.
Antibacterial chemicals, and poisons that deter herbivores.
10.Give an example of a plant that produces poisons to deter herbivores.
Foxgloves, deadly nightshade and tobacco plants all produce poisons.
11.Name three mechanical defences plants use.
Thorns and hairs that stop animals eating them, leaves that droop or curl when touched, and mimicry to trick animals.
12.How can drooping leaves defend a plant?
Sudden movement when touched can knock insects off, or scare a larger animal away.
13.Give an example of mimicry as a plant defence.
Some plants look like unhealthy plants so animals avoid them, and others mimic another organism so they are not eaten.
14.What are aphids and why are they a problem?
Insects that feed on the sap of a plant, removing nutrients and stunting growth. They can also spread viruses.
15.Why do plant diseases matter economically?
Diseased crops give lower yields, which means less food and financial loss for growers.
16.How can a testing kit identify a plant pathogen?
It contains monoclonal antibodies that bind to antigens on that specific pathogen, giving a visible result.
17.Why might a gardener remove and burn diseased leaves?
To stop the pathogen spreading to healthy parts of the plant or to other plants nearby.
18.How could you tell an ion deficiency from an infection?
A deficiency usually affects the whole plant evenly and improves when the missing mineral is supplied, whereas an infection often shows spots or decay and can spread to other plants.
19.Why do plants need nitrate ions specifically?
To make amino acids, which are joined together to make the proteins needed for growth.
20.What is chlorosis?
Yellowing of the leaves caused by a lack of chlorophyll, usually because of magnesium deficiency.
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