Flashcards · Biology
Plant Disease
-
Which pathogen should you know for a viral plant disease?
Tobacco mosaic virus.
-
Which is the fungal plant disease you should know?
Rose black spot.
-
Which insect pest should you know?
Aphids.
-
Name three signs of plant disease.
Any three of stunted growth, spots on leaves, rot, growths, malformed parts, discolouration, pests.
-
How can plant diseases be identified?
Gardening manual or website, laboratory tests, or testing kits with monoclonal antibodies.
-
How does a monoclonal antibody testing kit work?
The antibody binds to a particular pathogen and shows a colour change.
-
What are nitrate ions needed for?
To make amino acids, and then proteins, for growth.
-
What does a lack of nitrate cause?
Stunted growth.
-
What are magnesium ions needed for?
To make chlorophyll.
-
What does a lack of magnesium cause?
Chlorosis (yellow leaves).
-
What is chlorosis?
Leaves turning yellow because there is too little chlorophyll.
-
Why does a plant with chlorosis photosynthesise less?
It has less chlorophyll to absorb light.
-
How can a deficiency be treated?
By adding a fertiliser with the missing ion.
-
Why are pests a sign of disease?
Their presence can harm the plant and spread pathogens.
-
Which detection and identification methods are Higher tier?
The list of signs and the methods of identification.
-
Name the problem shown by the plant marked X and state its cause. Chlorosis, which is yellow leaves. It is caused by a lack of magnesium ions, which are needed to make chlorophyll.
-
Describe the symptoms and causes shown. 
Healthy plant. Nitrate deficiency: stunted growth, because nitrate is needed for proteins. Magnesium deficiency: yellow leaves (chlorosis), because magnesium is needed for chlorophyll.
-
What are the three groups of plant defences?
Physical, chemical and mechanical.
-
Name a physical defence of a plant.
Cellulose cell walls, a waxy cuticle or layers of dead cells.
-
How does the waxy cuticle protect a leaf?
It is a tough barrier that microorganisms cannot easily get through.
-
How do layers of dead cells protect a stem?
They form a barrier, then fall off, taking pathogens with them.
-
What is the bark of a tree made from?
Layers of dead cells.
-
Name two chemical defences.
Antibacterial chemicals and poisons to deter herbivores.
-
What is a herbivore?
An animal that eats plants.
-
Name a mechanical adaptation.
Thorns, hairs, leaves that droop or curl, or mimicry.
-
How do thorns protect a plant?
They deter animals from eating it.
-
Why do some leaves curl when touched?
It makes them harder to eat, and may scare animals away.
-
What is mimicry in plants?
A plant looks like something else, to trick animals.
-
Give an example of plant mimicry.
A passion flower leaf has markings that look like butterfly eggs, so butterflies avoid laying eggs on it.
-
Why do plants need defences?
They cannot move away from pathogens or animals that eat them.
-
Which defence stops microorganisms entering through the leaf surface?
The waxy cuticle.
-
Are plant cell walls made of cellulose?
Yes.
-
Name the type of defence marked X and say how it protects the plant. A mechanical adaptation, thorns. They deter animals from eating the plant.
-
Label the three types of plant defence and each example. 
Physical: cellulose cell wall, waxy cuticle, dead cells (bark). Chemical: antibacterial chemicals, poisons. Mechanical: thorns, hairs, leaves that curl.