Plant disease Flashcards
How do aphids cause damage to plants?
They use their sharp mouthparts to extract sap from the plant phloem, weakening the plant. They are also vectors who can transfer pathogens from diseased plants to healthy plants.
How can we reduce the number of aphids?
- Chemical pesticides.
- Biological pest control - using ladybirds.
Why do plants need a good supply of nitrate ions?
Nitrate ions are required to convert sugars into proteins which are required for the plant to grow. As a result, the growth of the plant will be stunted if there is not an adequate supply of nitrates.
Why do plants need a good supply of magnesium ions?
Magnesium ions are required to synthesise chlorophyll, which absorbs light energy during photosynthesis. As a result, the leaves cannot photosynthesis properly and they turn yellow (chlorosis).
What are the symptoms of disease in plants?
- Stunted growth (lack of nitrate ions).
- Spotted leaves (such as black spot fungus).
- Decay/rotting.
- Growths.
- Malformation of stems/leaves.
- Discolouration.
- Presence of pests.
What are three ways in which plant disease can be identified?
- Reference to a gardening website or manual.
- Laboratory testing.
- Monoclonal antibody test kits.
Give examples of physical defence responses used by plants
- Cellulose cell walls.
- Tough waxy cuticle on leaves.
- Outside layer on stems/bark on trees.
- Leaf fall.
Give examples of chemical defences responses used by plants
- Antibacterial chemicals.
- Poisons.
Give examples of mechanical defence responses used by plants
- Thorns and hairs to deter animals from eating it.
- Leaves that droop/curl on contact.
- Mimicry to trick animals.
