what is the purpose of the leaf cuticle? (3)
- prevents uncontrolled water loss
- ensures water does not collect on the leaf so that microbes do not collect there (as it will be damp)
- physical barrier to prevent pathogens from entering leaf
why is it important that leaf cuticle prevents pathogens passing through?
- so pathogens cannot have direct contact with epidermal cells
- less chance of infection
how does the leaf cuticle prevent water collecting on the surface? (and why is that important)
- is hydrophobic
- as fungal pathogens need standing water for spore germination
define a cell wall (in terms of plant defenses)
- structural barrier made of cellulose, which gives strength and flexibility and shape
- physical barrier preventing pathogens from entering
what does the cell wall contain?
a variety of chemical defences which activate rapidly when the cell detects pathogens
cellulose
give 4 examples of physical plant defences
- spike
- thorn
- stinging cells
- bark
difference between chemical and physical defences?
physical defences prevent microorganisms from entering
chemical defences are substances secreted by the plant that kill microorganisms
how does bark act as a physical defence?
external layer of dead cells that forms a barrier against infection
give 5 types of chemical defences in plants
- insect repellants
(repel insect vectors that carry disease) - insecticides (kill insects)
- antibacterial compounds
(kill bacteria) - antifungal compounds
(kill fungi) - poisons
how do anti microbial substances protect a plant from pathogens?
may kill the pathogen or prevent it from reproducing
can plants produce anti-microbial substances?
yes
what are the 4 main ways plant diseases can be detected and identified?
- observation
- microscopy
- DNA analysis
- identification of antigens, using monoclonal antibodies
define the term diagnosis
correctly identifying the existence of disease in an organism
how is observation used to identify plant diseases?
give advantages and disadvantages
- finding visual symptoms
adv - quick, cheap, easy
dis - similar symptoms for different diseases
not accurate
how is microscopy used to identify plant diseases?
identifying pathogen by looking at its shape
- electron gives better diagnosis than light
advantages and disadvantages of usinig microscopy to identify plant diseases? (in comparison to observation with naked eye)
adv - much more accurate
dis
- may be slower (sample must be given to lab)
- require equipment
downside of identifying plant diseases in the field?(visually/microscope)
only identified once symptoms are apparent (so plant is infected + may have spread)
how is DNA analysis used to identify plant diseases?
idea that…
- a map of the genome of the plant is produced
- can identify DNA of pathogen
- therefore can diagnose plant
how is antigen identification used to identify plant diseases?
- detect antigens (proteins) found on the surface of pathogens
- through chemical analysis which may use monoclonal antibodies
- as specific antigens are found on specific pathogens
why are plant lab tests useful?
and give one disadvantage
can identify the pathogen before it causes significant damage to the crop
- but can be slow + expensive
give 5 non-specific defence systems of the human body against pathogens
- and briefly describe what each of them do
1) skin (a physical barrier)
- dry, dead outer cells are difficult for pathogens to penetrate
2) acid in stomach
- contains strong HCL acid (kills almost all pathogens - ie. from food/drink/mucus)
3) cilia and mucus in airways
- mucus trap smaller microorganisms
- cilia moves up to throat + swallowed
4) nasal hairs
- keep out dust + larger micro-organisms
5) tears
- contain lysozymes (destroy bacteria cell wall)
what are non-specific defense mechanisms in the body?
responses that prevent the entry of all microorganisms (and preventing them from causing disease)
what key features does the skin have to kill pathogens? (2)
- produces antimicrobial secretions (sweat)
- natural (not harmful) microorganisms which outcompete pathogens for resources
what are platelets (and where are they made)?
- small fragementsof cells
- made in the bone marrow
- which help blood to clot
