plant disease

Question 1

How do aphids (insects) cause damage to plants?

Answer 1

They use their sharp mouthparts to extract sap from the plant phloem, weakening the plant, and stunting its growth.
They are also vectors who can transfer pathogens from diseased plants to healthy plants.

Question 2

How can we reduce the number of aphids?

Answer 2

● Chemical pesticides

● Biological pest control - using ladybirds

Question 3

Why do plants need a good supply of nitrate ions?

Answer 3

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.

Question 4

Why do plants need a good supply of magnesium ions?

Answer 4

Magnesium ions are required to synthesise
chlorophyll, which absorbs light energy during photosynthesis.
As a result, the leaves cannot photosynthesise properly and they turn yellow (chlorosis).

Question 5

What are the symptoms of disease in plants?

Answer 5

● Stunted growth (lack of nitrate ions)
● Spotted leaves (eg. rose black spot fungus)
● Decay/rotting
● Growths
● Malformation of stems/leaves
● Discolouration
● Presence of pests

Question 6

What are three ways in which plant disease

can be identified?

Answer 6

● Reference to a gardening website or manual
● Laboratory testing
● Monoclonal antibody test kits

Question 7

Give examples of physical defence

responses used by plants

Answer 7

● Cellulose cell walls
● Tough waxy cuticle on leaves
● Outside layer on stems/bark on trees
● Leaf fall

Question 8

Give examples of chemical defence

responses used by plants

Answer 8

● Antibacterial chemicals

● Poisons

Question 9

Give examples of mechanical defence

responses used by plants

Answer 9

● Thorns and hairs to deter animals
● Leaves that droop/curl on contact
● Mimicry to trick animals