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Plant responses to herbivory - Coggle Diagram
Plant responses to herbivory
Physical
Includes thorns and spines, fibrous/inedible tissue, hairy leaves and stings
Protects plant from herbivory by damaging anything that tries to eat it
Chemical
Alkaloids
Bitter tasting nitrogenous compounds
Include caffeine, nicotine, cocaine and morphine
Caffeine is toxic to fungi and insects
Nicotine is a toxin released when a leaf is eaten
Terpenoids
Often toxins for fungi and insects
Pyrethrin is an insect neurotoxin
Citronella is an insect repellant
Tannins
Bitter taste
Toxic to insects
Tea and red wine are high in tannins
Pheromones and Volatile Organic Compounds (VOCs)
If maple trees are attacked by insects, they release a pheromone which causes nearby cells to produce callose and other similar chemicals to protect themselves
When cabbages are attacked by the caterpillars of the white cabbage butterfly, they produce a chemical signal which attracts a parasitic wasp. This wasp lays its eggs in the caterpillars so that they are eaten alive, protecting the plant in the process. they produce a different signal to attract a different wasp if they are attacked by the mealy cabbage greenfly
When apple trees are attacked by spider mites, they produce VOCs that attract predatory mites to kill the pests
Some wheat seedling produce VOCs when attacked by aphids which repel other aphids
Touch sensetivity
Mimosa pudica
When this plant's leaves are touched, they fold down and collapse very quickly
Touching the leaves causes the active transport of potassium ions to the other side of the leaf
this changes the water potential, and water follows the potassium ions, causing one side to become more turgid, and the other to become more flaccid
This may be in order to scare herbivores or dislodge small insects
Over about 12 minutes, the potassium ions move back, and so does the water, restoring the shape of the leaf
They collapse in a few seconds, and are restored in around 10-12 minutes