3.3 Plant Disease

Question 1

How do aphids cause damage to plants?

Answer 1

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

Question 2

How can we reduce the number of aphids?

Answer 2

By chemical pesticides and biological pest control, e.g. 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. so if there is not adequate supply of nitrates the growth of the plant will be stunted

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. so if there is not enough magnesium, the leaves cannot photosynthesis 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 (rose black spot fungus
-Decay/rotting
-Growths
-Malformation of stems/leaves
-discolouration
-presence of pests

Question 6

what are three ways i which plant disease can be identified?

Answer 6

-reference to a gardening manual
-laboratory testing
-monoclonal antibody test kits

Question 7

Give examples of physical defence responses used by plants

Answer 7

-cellulose walls
-tough waxy cuticle on leaves
-outside layer on stems/bark on trees
-leaf falls

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