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Plant diseases + defences (Symptoms of plant diseases (Stunted growth,…
Plant diseases + defences
Plants need mineral ions, otherwise they will suffer from deficiency symptoms
Nitrates are needed for proteins and therefore growth
Lack of nitrates = stunted growth
Magnesium ions are needed to make chlorophyll so photosynthesis can happen
Lack of magnesium ions = yellow leaves/discolouration
Vectors, such as aphids, transfer diseases between plants
Aphids have sharp mouthparts which penetrate the phloem vessels of the plant to feed on the sugar-rich sap. As they attack in large numbers, this leaves the plant without enough products for photosynthesis, damaging and weakening the plant
Can be destroyed with chemical pesticides or by releasing aphid-eating insects such as ladybirds
Symptoms of plant diseases
Stunted growth
Spots on leaves
areas of decay/rotting
growths
malformed stems and leaves
discolouration
presence of visible pests e.g aphids
Plant diseases can be identified by taking the plant to a laboratory where scientists can find out the pathogen causing the disease
Plant defences
Physical barriers
Cell walls help resist invasion of microorganisms
Tough waxy cuticle
Layer of dead cells around stems (e.g bark) to prevent pathogens from penetrating stem. When these dead cells shed, the pathogens fall of with them
Leaf loss ensures any pathogens living on leaves fall off
Chemical defences
May produce antibacterial chemicals e.g witch hazel
Can produce poisons which deter herbivores
Mechanical defences
Thorns + hairs prevent animals from eating the plant/laying eggs
Some plants have leaves which droop and curl when touched, knocking off any insects and scaring off larger animals, as well as tricking animals into thinking they are unhealthy (to prevent them eating them)
Mimic other organisms e.g some plants develop yellow spots on their leaves that resemble butterfly eggs to prevent butterflies from laying their eggs on them