Plant disease

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Plant Pathogens and Pests

Plants can be infected by viral, bacterial and fungal pathogens, and can also be infested by insects.
Tobacco mosaic virus (TMV) is a viral pathogen that causes a mosaic pattern of discolouration on leaves.
Rose black spot is a fungal disease that causes black spots on leaves.
Aphids are insects that feed on plant sap; they have long sharp mouthpieces that pierce the stem and reach the phloem.
Aphids can remove large quantities of phloem sap, which weakens the plant and reduces growth.
Aphids can also act as vectors, transferring diseases from plant to plant.

Detecting Plant Diseases

Detecting and treating plant infections quickly is important to reduce damage.
Common symptoms of plant disease include stunted growth, spots on leaves, areas of decay (rot), growths, malformed stems or leaves, discolouration, and the presence of pests.
Symptoms can be caused by more than one disease, making identification difficult.
In gardens, diseases can be identified by comparing symptoms with those described in gardening manuals or online.
For crops or forest trees, experts may take samples to a laboratory for DNA analysis to identify the specific pathogen.
Testing kits containing monoclonal antibodies can be used to identify pathogens quickly and easily.

Mineral Deficiencies in Plants

Plants need the correct amount of nutrients to function properly.
Nitrate deficiency causes stunted growth because nitrate ions are needed for protein synthesis and therefore growth.
Magnesium deficiency causes chlorosis (yellowing of leaves) because magnesium ions are needed to make chlorophyll.
Mineral deficiencies can be treated by adding fertilisers to the soil.
Fertilisers are often shown as NPK ratios (nitrogen, phosphorus, potassium) depending on the needs of the plant.
When choosing a fertiliser, match the symptoms to the mineral deficiency: e.g. stunted roots indicate potassium deficiency, lack of flowers/fruits indicates phosphate deficiency.

Mineral deficiencies in plants

Physical Plant Defences

Plants have physical defences that prevent pathogens from entering.
The cellulose cell wall provides support and protection from microorganisms.
The waxy cuticle on leaves is a barrier to microbes; the only entry point is through the stomata.
Bark is a tough layer of dead cells around the stem that prevents pathogens from entering.
Deciduous trees lose their leaves in winter, which can remove infections along with the leaves.

Chemical Plant Defences

Many plants produce chemicals with antimicrobial properties that kill or inhibit pathogens.
Some plants produce poisons to deter herbivores from eating them.
Examples of plants with antimicrobial chemicals include tea tree oil, mint and witch hazel.
Plants are being studied as potential sources of new antibiotics as more bacteria become resistant to current ones.

Mechanical Adaptations Against Herbivores

Mechanical adaptations help plants avoid being eaten by herbivores.
Thorns and hairs deter animals from feeding.
Some leaves droop or curl when touched, which can dislodge insects or make the plant less appealing.
Mimicry can trick animals; for example, some plants have spots that mimic butterfly eggs, so butterflies do not lay their eggs on the leaves.
Defences against herbivores also help defend against pathogens because they prevent damage that would allow pathogens to enter.

Effects of Plant Diseases

Plant diseases can reduce yield for farmers, leading to financial loss.
TMV causes a mosaic pattern of discolouration on leaves and can reduce chlorophyll production.
Reduced chlorophyll means less photosynthesis, so the plant has less energy for growth, resulting in stunted growth.
Aphid infestations can weaken plants by removing sap and can transmit diseases.
Mineral deficiencies can also reduce yield; for example, nitrate deficiency causes stunted growth.

Controlling Pests and Diseases

Chemical pesticides are poisons sprayed onto plants; they kill all insects, including beneficial ones.
Biological control involves releasing natural predators, such as ladybirds, to eat aphids.
Biological control is specific to the pest and does not harm other insects, but it may take longer to work.
Chemical pesticides can harm non-target species and may need repeated application.
To prevent the spread of disease, tools should be disinfected after use on infected plants.
For TMV, disinfecting tools kills the virus and prevents it from being transferred to healthy plants.

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Soal latihan

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1.Which mineral ion deficiency causes chlorosis in plants?
Easy
- AMagnesium
- BNitrate
- CPhosphate
- DPotassium
2.Which mineral ion deficiency causes stunted growth in plants?
Easy
- ANitrate
- BMagnesium
- CCalcium
- DIron
3.What is chlorosis?
Easy
- AYellowing of leaves due to lack of chlorophyll
- BDeath of leaf tissue causing black spots
- CStunted growth due to lack of proteins
- DCurling of leaves due to viral infection
4.Aphids are a type of insect pest that can act as vectors for plant diseases.
Easy
True or false?
5.Which of the following is a physical defence of a plant against pathogens?
Easy
- ACellulose cell wall
- BProduction of antibacterial chemicals
- CThorns
- DDrooping leaves when touched
6.Which of the following is a chemical defence of a plant against pathogens?
Easy
- AAntibacterial chemicals
- BWaxy cuticle
- CBark
- DCellulose cell wall
7.Which of the following is a mechanical adaptation against herbivores?
Easy
- AThorns
- BWaxy cuticle
- CCellulose cell wall
- DProduction of caffeine
8.Which of the following are symptoms of plant disease? (select all that apply)
Easy
- AStunted growth
- BSpots on leaves
- CAreas of decay (rot)
- DIncreased flowering
- EMalformed stems or leaves

Soal lainnya

9.Which of the following can be used to identify a plant disease? (select all that apply)
Easy
- AReference to a gardening manual or website
- BTaking infected plants to a laboratory for DNA analysis
- CUsing testing kits containing monoclonal antibodies
- DMeasuring the height of the plant
- ECounting the number of leaves
10.Which of the following are physical plant defence responses? (select all that apply)
Medium
- ACellulose cell walls
- BTough waxy cuticle on leaves
- CLayers of dead cells around stems (bark)
- DProduction of antibacterial chemicals
- EProduction of poisons to deter herbivores
11.Which of the following are mechanical adaptations against herbivores? (select all that apply)
Medium
- AThorns
- BHairs
- CLeaves that droop or curl when touched
- DMimicry of butterfly eggs
- EProduction of caffeine
12.Magnesium deficiency causes stunted growth in plants.
Easy
True or false?
13.Match each plant disease or pest to the type of organism that causes it.
Medium
- Tobacco mosaic virus
- Rose black spot
- Aphid
- Virus
- Fungus
- Insect
14.Which of the following are symptoms that can indicate a plant is diseased? (select all that apply)
Medium
- AStunted growth
- BSpots on leaves
- CAreas of decay (rot)
- DGrowths
- EIncreased flowering
15.Place the steps in the correct order to identify a plant disease using a laboratory test.
Medium
- Collect a sample from the infected plant
- Send the sample to a laboratory
- Perform DNA analysis on the sample
- Identify the specific pathogen
16.A farmer notices that some crop plants have yellow leaves and poor growth. Tests show the plants are deficient in magnesium. Which symptom is directly caused by magnesium deficiency?
Hard
- AChlorosis
- BStunted growth
- CAreas of decay
- DGrowths on stems
17.Which of the following are physical defence responses of plants against pathogens? (select all that apply)
Medium
- ACellulose cell walls
- BTough waxy cuticle on leaves
- CLayers of dead cells around stems (bark)
- DProduction of antibacterial chemicals
- EPoisonous chemicals to deter herbivores
18.Aphids have long sharp mouthpieces that pierce the stem and feed on phloem sap.
Easy
True or false?
19.How do aphids feed on the rose plant?
Medium
- AThey pierce the stem and feed on phloem sap
- BThey chew the leaves and eat the cellulose
- CThey suck water from the xylem
- DThey absorb nutrients through the roots
20.The gardener wants to control the aphids without using chemicals. Which method is an example of biological pest control?
Medium
- ASpraying the roses with a chemical pesticide
- BReleasing ladybirds into the garden
- CRemoving the affected leaves by hand
- DWatering the plants more frequently
21.Plants have an immune system similar to that of animals.
Easy
True or false?
22.A gardener's tomato plants have yellow leaves and poor growth. Tests show a magnesium deficiency. Which symptom is directly caused by the magnesium deficiency?
Medium
- AChlorosis
- BStunted growth
- CAreas of decay
- DGrowths on the stems
23.Aphids feed on plant sap. Which part of the plant do they pierce with their mouthpieces to reach the sap?
Medium
- AXylem
- BPhloem
- CPalisade mesophyll
- DStomata
24.Which of the following are symptoms that can indicate a plant is infected with a disease? (select all that apply)
Medium
- AStunted growth
- BSpots on leaves
- CAreas of decay
- DIncreased flower production
- EPresence of pests
25.A plant with stunted growth is most likely deficient in nitrate ions.
Medium
True or false?
26.Match each plant defence to its correct category.
Medium
- Cellulose cell wall
- Production of antibacterial chemicals
- Thorns and hairs
- Physical defence
- Chemical defence
- Mechanical adaptation
27.Place the steps in the correct order for identifying a plant disease using a laboratory test.
Medium
- Collect a sample from the infected plant
- Send the sample to a laboratory
- Perform DNA analysis on the sample
- Identify the specific pathogen
28.A farmer's crop plants have yellow leaves and poor growth. A soil test shows low magnesium. Which fertiliser should the farmer apply to treat the yellowing?
Hard
- AA fertiliser high in magnesium
- BA fertiliser high in nitrate
- CA fertiliser high in phosphate
- DA fertiliser high in potassium
29.Which of the following is the best way to control the aphid infestation without using chemicals?
Medium
- ARelease ladybirds into the garden
- BSpray the plants with pesticide
- CRemove all the leaves
- DWater the plants more often
30.Aphids can transfer diseases between plants.
Medium
True or false?
31.Which of the following are mechanical adaptations that help protect a plant from herbivores? (select all that apply)
Medium
- AThorns
- BHairs
- CLeaves that droop or curl when touched
- DProduction of antibacterial chemicals
32.A gardener's tomato plants have yellowing leaves and poor growth. A soil test shows low magnesium. Which fertiliser should the farmer apply to treat the yellowing?
Medium
- AMagnesium-containing fertiliser
- BNitrate-rich fertiliser
- CPhosphate-rich fertiliser
- DPotassium-rich fertiliser
33.A plant pathologist wants to identify the pathogen infecting a crop. Which methods could be used? (select all that apply)
Medium
- AComparing symptoms with a gardening manual or website
- BSending a sample to a laboratory for DNA analysis
- CUsing a testing kit containing monoclonal antibodies
- DMeasuring the plant's height with a ruler
- ECounting the number of leaves on the plant
34.Aphids are insects that feed on plant sap and can act as vectors for plant diseases.
Easy
True or false?
35.A plant has stunted growth but its leaves are green. Which mineral ion deficiency is most likely?
Medium
- AMagnesium deficiency
- BNitrate deficiency
- CPotassium deficiency
- DPhosphate deficiency
36.A farmer's crop plants have yellow leaves and poor growth. Tests show the plants are deficient in magnesium. Which symptom is directly caused by the magnesium deficiency?
Hard
- AYellow leaves (chlorosis)
- BPoor growth (stunted growth)
- CSpots on leaves
- DAreas of decay
37.A farmer notices that some crop plants have yellow leaves and poor growth. Tests show the plants are deficient in magnesium. Which symptom is directly caused by the magnesium deficiency?
Hard
- AYellow leaves (chlorosis)
- BPoor growth (stunted growth)
- CSpots on leaves
- DAreas of decay
38.Which term describes the yellowing of plant leaves caused by a lack of magnesium ions?
Easy
- AChlorosis
- BNecrosis
- CDecay
- DMalformation
39.A plant has stunted growth but its leaves remain green. Which mineral ion is it most likely to be deficient in?
Easy
- ANitrate
- BMagnesium
- CPotassium
- DPhosphate
40.Which of the following is a symptom of tobacco mosaic virus (TMV) infection?
Easy
- AA mosaic pattern of discolouration on the leaves
- BBlack streaks on the leaves
- CA sticky residue on the stems
- DSmall yellow spots that mimic butterfly eggs
41.A farmer uses a fertiliser with an NPK ratio of 3:1:2. If the fertiliser contains 30% nitrogen, what percentage of potassium does it contain?
Medium
42.Complete the sentence about plant defence.
Medium
The waxy ____ on the surface of leaves acts as a physical barrier to pathogens.
43.Name the type of organism that causes rose black spot.
Medium
44.A fertiliser has an NPK ratio of 5:3:2. If it contains 25% nitrogen, what percentage of potassium does it contain?
Medium
45.Complete the sentence about how a plant defends itself against pathogens.
Medium
The waxy ____ on the surface of a leaf acts as a physical barrier to prevent pathogens from entering.
46.Name the chemical defence produced by some plants that kills insects that eat them.
Medium
47.Complete the sentence about aphids feeding on a plant.
Easy
Aphids have long sharp mouthpieces that pierce the stem and enter the ____ so that they can feed on the sugar-filled sap.
48.Complete the sentence about how aphids can affect plants.
Easy
Aphids can act as a ____ for the transfer of diseases between plants.
49.Name the virus that causes a common plant disease with mosaic-patterned leaves.
Medium
50.Name the fungal pathogen that causes rose black spot.
Medium
51.Name the mineral ion that plants need to make chlorophyll.
Medium
52.Name the mineral ion that plants need for protein synthesis and therefore growth.
Medium
53.Describe how a gardener could identify the disease affecting their plants.
Hard
54.Explain how a plant's physical defences reduce the chance of infection by pathogens.
Hard
55.Suggest why having a mimicry of butterfly eggs on the leaves might benefit the plant.
Hard
56.Suggest why this stage of the plant lifecycle benefits from having such a high concentration of caffeine.
Hard
57.A farmer uses a fertiliser with an NPK ratio of 3:1:2. If the fertiliser contains 30% nitrogen, what percentage of potassium does it contain?
Medium
- A20 %
- B18 %
- C24 %
- D22 %
58.A fertiliser has an NPK ratio of 5:3:2. If it contains 25% nitrogen, what percentage of potassium does it contain?
Medium
- A9 %
- B10 %
- C12 %
- D11 %

Kartu flash

What is the main symptom of tobacco mosaic virus (TMV) in plants?

A distinctive mosaic pattern of discolouration on the leaves, often with a yellowing or mottling appearance.

What type of pathogen causes rose black spot?

A fungus.

What are the visible symptoms of rose black spot?

Purple or black spots on the leaves, which can cause the leaves to turn yellow and drop off.

What are aphids and how do they damage plants?

Aphids are small insects that pierce plant stems and feed on sugar-filled phloem sap, removing large quantities and weakening the plant.

Why are aphids described as vectors?

They carry pathogens from plant to plant as they feed, transferring disease between plants.

Name two methods used to control aphid infestations.

Chemical pesticides and biological pest control using ladybirds (a natural predator of aphids).

What is chlorosis and what mineral deficiency causes it?

Chlorosis is the yellowing of leaves caused by a magnesium deficiency.

What is the role of magnesium ions in plants?

Magnesium ions are needed to make chlorophyll, which is essential for photosynthesis.

What symptom is caused by a nitrate deficiency in plants?

Stunted growth.

Why does a nitrate deficiency cause stunted growth?

Nitrate ions are needed for protein synthesis, which is required for growth.

How can mineral deficiencies in plants be corrected?

By adding fertilisers to the soil, often chosen using NPK ratios based on the plant's needs.

List four general symptoms that can indicate a plant disease.

Stunted growth, spots on leaves, areas of decay (rot), and discolouration. Other symptoms include growths, malformed stems or leaves, and the presence of pests.

How can a gardener identify a plant disease by comparing symptoms?

By referring to a gardening manual or a website to match the symptoms to a known disease.

How are monoclonal antibodies used to identify plant diseases?

Testing kits containing monoclonal antibodies can quickly and easily detect the presence of specific pathogens.

How can experts identify the pathogen infecting crop plants or forest trees?

They take samples from the field or woodland to a laboratory for DNA analysis.

What is the role of the cellulose cell wall as a plant defence?

It provides a physical barrier that protects the plant from microorganisms.

How does the waxy cuticle defend a leaf against pathogens?

It acts as a physical barrier preventing microbes from entering; the only entry point is through the stomata.

How does bark protect a plant stem?

Bark is a tough layer of dead cells around the stem that prevents pathogens from entering.

How do deciduous trees use leaf loss as a defence against infection?

When deciduous trees lose their leaves in winter, any infection in those leaves is removed with them.

What are chemical plant defences? Give an example.

Many plants produce chemicals with antimicrobial properties, such as antibacterial chemicals, that defend against pathogens.

Give two mechanical adaptations that deter herbivores.

Thorns and hairs deter animals from eating the plant.

What is meant by mimicry as a plant defence? Give an example.

The plant evolves a feature that tricks animals; for example, the passion flower has yellow spots on its leaves that mimic butterfly eggs, deterring butterflies from laying real eggs there.

Why does a defence against herbivores also help defend against pathogens?

Herbivores can damage plant tissues, creating entry points for pathogens; by preventing herbivore damage, the plant also reduces the chance of pathogen entry.

Why do coffee seedlings have a high concentration of caffeine?

Caffeine is a poisonous chemical that kills insects; young seedlings are vulnerable and benefit most from this protection.

Why does caffeine in the soil around a coffee plant benefit the plant?

It prevents seeds from germinating in that region, reducing competition for resources.

What is the role of the vacuole in a plant cell besides storage?

It helps support the plant cell by making it turgid.

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