plant and disease & defences TOPIC 3 Flashcards
what type of pathogens can cause disease
- bacteria
- virus
- fungi
what organisms can cause disease
- worms
- insects
(indirectly)
what are signs of plant disease
- stunted growth
- spots on leaves
- areas of decay
- abnormal growths
- malformed leaves
- malformed stems
- discolouration of leaves
- presence of pests
what is the fungi disease for plants
rose black spot
what pathogen causes rose black spot
fungi
give some symptoms of rose black spot
- purple or black spots on leaves
- leaves turn yellow and drop early
explain why the symptoms of rose black spot are bad
- reduces area available for photosynthesis
- less energy
- less flowering
how is rose black spot transmitted
spores of the fungus spread by the wind or in rain
how is rose black spot treated and prevented
- chemical fungicide
- removing and burning affected leaves and stems
why is it a good idea to burn rose black spot infected leaves
the spores saty dormant over winter on dead leaves and on hte stems of rose plants so can infect again in summer
what is the viral disease for plants
tobacco mosaic virus
what pathogen causes the tobacco mosaic virus
virus
what plants does the tobacco mosaic virus affect
tomato and tobacco
what are the symtpoms of the tobacco mosaic virus (TMV)
- small patched of light green, brown and yellow appear on the leaves
- unusual growth ~ leaves are smaller than usual
why are the symptoms for TMV bad
- less area for photosynthesis
- reduced yield
how is TMV transmitted
the disease is spread by contact from plant to plant: direct and indirect (vectors)
how can TMV be treated and prevented
- there is no treatment but farmers grow TMV resistant strains of crop
- good field hygiene and pest control stop the spred
- brun any leaves suspected of being infected
other than viruses, bacteria and fungi; give another way plants can be damaged
by pests = aphids
what is the name given to the pests which bring damage to plants
aphids
how can aphids damage plants
- destroy plants directly by eating them
- act as vectors of disease
describe how aphids are specialised to damage and weaken plants
- have sharp mouthparts that penetrate the phloem vessels to feed on the sap
- attack in huge numbers, depriving the plant of products of photosynthesis
how can aphids be removed from an evironment to prevent plant damage
- using chemical pesticides
- using biological pest control: releasing aphid-eating insects to control the aphid population
give an insect which can control the aphid population by eating them
lady bugs
give another plant pest other than aphids which damage plants
nematode worms
how do nematode worms damage plants
feed in or on plant roots = damage and cannot absorb water and mineral ions effectively = fails to grow
give all the ways plants can suffer from disease
- viruses
- bacteria
- fungi
- pests = aphids & worms
- mineral deficiency (non-communicable diease)
what is the plant version of a non-comunicable disease
mineral deficiencies
why do plants need nitrate ions
- they convert sugars made in photosynthesis into amino acids
- amino acids are needed to make proteins
- proteins are used for growth
- = growth stunted & crop not produced efficiently
why do plants need magnesium ions
- magnesium ions make chlorophyll
- chlorophyll needed to absorb light in photosynthesis
- leaves = yellow
what is the term used for when leaves yellow due to lack of magnesium ions
chlorosis
what are the two most important ions to a plant
- nitrate
- magnesium
