A-level Biology - 3.2.9 The Role of Aphids in Spreading Plant Viruses
Plant viruses are made up of a nucleic acid core (usually RNA or DNA) surrounded by a protective protein coat called a capsid. Some plant viruses may also have an outer lipid membrane (envelope), although this is less common.
Describe the structure of plant viruses
Consist of nucleic acid and protein coat & sometimes outer membrane
Key Terms
Describe the structure of plant viruses
Consist of nucleic acid and protein coat & sometimes outer membrane
How can plant viruses enter plants?
Only through damaged sites or by using vectors
Once inside the plant, what can viruses do (i.e. related to spreading/transmission)?
Can spread throughout plant & can be transmitted to next generation through seeds and vegetative reproductive structures (e.g. tubers)
Name 2 symptoms plant virus diseases
Yellowing in leaves
(known as chlorosis)
Distortion of parts of plant
e.g. leaf roll, malformation of flower and fruit
What do plant virus diseases do to plants and what does this lead to (economically)?
Decreases photosynthetic efficiency
Reduces no. of grains and size of grain = loss of yield
Decreases value of crops
Describe the lifecycle of an aphid in the spring & summer
Clone themselves
Produce genetically identical daughter
Asexual reproduction
Half the clones born with wings to migrate to start ...
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| Term | Definition |
|---|---|
Describe the structure of plant viruses | Consist of nucleic acid and protein coat & sometimes outer membrane |
How can plant viruses enter plants? | Only through damaged sites or by using vectors |
Once inside the plant, what can viruses do (i.e. related to spreading/transmission)? | Can spread throughout plant & can be transmitted to next generation through seeds and vegetative reproductive structures (e.g. tubers) |
Name 2 symptoms plant virus diseases | Yellowing in leaves (known as chlorosis) Distortion of parts of plant e.g. leaf roll, malformation of flower and fruit |
What do plant virus diseases do to plants and what does this lead to (economically)? | Decreases photosynthetic efficiency Reduces no. of grains and size of grain = loss of yield Decreases value of crops |
Describe the lifecycle of an aphid in the spring & summer | Clone themselves Produce genetically identical daughter Asexual reproduction Half the clones born with wings to migrate to start colonies on a new host plant |
Describe the lifecycle of an aphid in the autumn & winter | Produce males and females to increase genetic variation Sexual reproduction Need huge stock of embryos that genetically different to increase chance of survival |
What does an aphid’s stylet consist of? | Saliva canal and feeding canal |
What happens to the stylet as it penetrates the tissues to reach the phloem? | Saliva gels around it |
Describe how aphids feed | Insert their stylet (mouthparts) into phloem Phloem vessel is punctured, sap which is under high pressure = forced into aphid’s gut |
Name 3 ways how aphids reduce yields of crops | Remove phloem sap Deprives plant of sugars and amino acids Encourage growth of moulds on leaves Reduces photosynthesis Transmitting plant viruses |
Why can plant viruses only enter plant cells if they’re damaged? | Plant cell walls are too thick to enter |