Plant Diseases

Question 1

why do plants have a waxy cuticle

Answer 1

• it provides a barrier to stop pathogens from entering them

- it also stops water collection on the leaf which could reduce risk of infection by pathogens

Question 2

why are plant cells surrounded by cell walls made from cellulose

Answer 2

it forms a physical barrier against the pathogens that make it past the waxy cuticle

Question 3

what are the two types of defences that plants use

Answer 3

physical and chemical

Question 4

what do chemical defences do

Answer 4

help prevent damages to the plant

Question 5

what are the two examples of plants using chemicals to defend themselves

Answer 5

• they produce antiseptics which kill bacterial and fungal pathogens
• they also produce chemicals to deter pests from feeding on their leaves

Question 6

where does quinine come from and what has it been used for

Answer 6

• it comes from the bark of the cinchona tree

- for years it was the main treatment for malaria

Question 7

where does aspirin come from and what has it been used for

Answer 7

• it was developed from a chemical found in the bark and leaves of willow tress
• it is used to relieve pain and fevers

Question 8

in the field, what are plant diseases usually detected by

Answer 8

observations

Question 9

how might a plant pathologist deduct observing galls (abnormal growths) on a tree

Answer 9

• it might indicate crown gall disease

- especially in apple and other fruit tress

Question 10

what is usually the cause of plants showing symptoms of a disease such as yellow leaves

Answer 10

environmental causes such as nutrient deficiency

Question 11

what is possible when changing the environmental conditions, like adding nutrients to the soil, and observing any change in a plants symptoms of a disease

Answer 11

it is possible to determine whether a a plant is diseased or if the symptoms were due to something else

Question 12

why can plant pathologists analyse the distribution of diseased plants to identify the kind of pathogen involved

Answer 12

because different pathogens are spread in different kinds of ways

Question 13

what would patches of diseased plants suggest about how the pathogen was spread

Answer 13

it suggests that it was spread through the soil

Question 14

what would a random distribution of diseased plants suggest about how the pathogen was spread

Answer 14

it suggests that it was an airborne pathogen

Question 15

what does laboratory based diagnostic testing allow

Answer 15

the accurate identification of specific pathogens

Question 16

how does the detection of antigens work when diagnostically testing for pathogens

Answer 16

• pathogens have unique molecules on their surface called antigens
• antigens from a specific pathogen will be present in a plant infected with that pathogen
• it can be detected in a sample of plant tissue using monoclonal antibodies
• detection of unique antigens allows pathogen to be identified so the disease is diagnosed

Question 17

how does the detection of DNA work when diagnostically testing for pathogens

Answer 17

• if a plant is infected with a pathogen, the pathogens DNA will be present in the plant’s tissues
• scientists have techniques that allow them to detect small amounts of pathogen DNA in a sample of tissue
• allowing them to identify the particular pathogen that is present