Paper 1: Topic 3 Infection & response - Plant disease and defence (IV form) Flashcards
List 3 mineral ions that plants need to maintain healthy growth
Potassium ions
Magnesium ions
Nitrate ions
Explain why plants need potassium ions
To produce some enzymes
To produce fruits and flowers
Explain why plants need nitrate ions
To produce amino acids to make new proteins
To produce nucleotides to make DNA
Explain why plants needs magnesium ions
To produce chlorophyll to allow the plant to photosynthesise
Describe and explain the signs of a lack of magnesium ions in plants
Description:
Yellowing of the leaves
Chlorosis occurs
Explanation:
Due to a lack of chlorophyll production the leaves do not have a green colour
Describe the signs of a lack of potassium ions in plants
Lack of fruits and flowers
Stunted growth
Describe and explain the signs of a lack of nitrate ions in plants
Description:
Stunted growth
Explanation:
Due to a lack of proteins for growth and repair of tissues and organs
State 3 types of pathogens that can cause diseases in plants
Fungi
Bacteria
Viruses
Define the term pathogen
A micro-organism that causes disease
State reasons how a plant may be infested
Insect infestation
Aphid infestation
State 7 general signs of disease in a plant
- Stunted growth
- Spots on leaves
- Patches of decay (called rot)
- Abnormal growths e.g. calluses
- Malformed stems and leaves
- Discolouration of stems and leaves
- Presence of pests
State 3 methods a gardener can use to identify a disease in his their plant(s)
- Consult a gardening manual or gardening website
- Take the infected plant to a specialised laboratory for testing
- Use a testing kit that uses monoclonal antibodies to detect the presence of a specific antigen
State the 3 types of defence a plant has
- Chemical defence
- Physical defence
- Mechanical defence
State 3 examples of physical defence mechanisms in plants
- Tough waxy cuticle
- Cellulose cell walls
- Layers of dead cells around their stems e.g. bark
HINT: do not say these defences prevents PREADTORS eating them herbivores do not hunt plants :)
State 2 examples of chemical defence mechanisms in plants
Production of antibacterial chemicals e.g. mint plant, witch hazel plant
Production of poisons e.g. tobacco plants, foxgloves and deadly nightshade plants
State 3 examples of mechanical defence mechanisms by plants
- Thorns and hairs
- Drooping or curling their leaves when touched
- Mimicry
HINT: do not say these defences prevent PREADTORS eating them herbivores do not hunt plants :)
What type of defence mechanism does an ice plant use?
Mechanical defence – using mimicry the ice plants resemble stones and rocks and hence avoid being eaten by herbivores HINT: do not say these defences prevents PREADTORS eating them herbivores do not hunt plants
Explain how thorns and hairs act as a form of plant defence
Prevent herbivores touching and eating them e.g. cacti, rose bush
Form of mechanical defence
Explain how drooping or curling their leaves when touched is a defence mechanism in plants
This is used to knock insects off their leaves to prevent the inset eating the leaves e.g. mimosa plant
Form of mechanical defence
Exalpain how plant mimicry is a form of plant defence
The plant mimics certain characteristics e.g. passion flower has yellow spots on its leaves which look like butterfly eggs. Butterflies then avoid laying eggs on those leaves as they think there will be competition between the caterpillars for food!
This is a form of mechanical defence
HINT: do not say these defences prevent PREADTORS eating them herbivores do not hunt plants :)
Explain how chemical defence mechanisms used in plants
Production of antibacterial chemicals kill any bacteria that penetrate the waxy cuticle and cell walls
Production of poisons deter herbivores from eating them e.g. tobacco plants, foxgloves and deadly nightshade plants
Explain how plants use physical defnece mechanisms to protect themselves
Tough waxy cuticle – forms a barrier to prevent the entry of pathogens
Cellulose cell walls – surround every plant cell to form a physical barrier to any pathogen that may have passed through the waxy cuticle
Layers of dead cells around their stems e.g. bark – to form a physical barrier to prevent pathogens entering the plant
Name a plant disease caused by a virus
Tobaco Mosaic
Describe 2 symptoms of Tobacco Mosaic disease
- Discoloured leaves
- Stunted growth
Explain why plants with tobacco mosaic virus often have stunted growth
- The discolouration of the leaves cuases there to be less chloroplhyll in the leaves
- This means the plant photosynthesise less
- This means they produce less glucose
- So there is less energy for the production of new cells and the production of new proteins
- So there is less growth
Name a plant disease caused by a fungus
Rose black spot
Describe the symptoms of rose black spot disease
- Black or purple spots on the leaves
- Leaves turn yellow
- Leaves fall of the plant early (called ‘early drop’)
Explain the lack of growth that is often seen in roses with black spot disease
The yellowing of the leaves causes there to be less chloroplhyll in the leaves
This means the plant photosynthesise less
This means they produce less glucose
So there is less energy for the production of new cells and the production of new proteins
So there is less growth
This gets worse as leaves fall off the plant
Describe how rose black spot disease is spread
- The fungus can spread through water
- The fungus can spread through the air
Describe 3 actions gardeners can take to treat rose black spot disease
- Gardeners can apply fungicides to infected plants
- They should also strip off any affected leaves from the plant
- The infected leaves must then be dedtoyed to prevent further spread of the fungus
