Module 5.5 Part 5 (Plants)

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  • Module 5.5 Plant and Animal Responses (part 5)
    • Plant stimuli
      • no  sensory organs
      • Abiotic = non-living stimuli
      • Biotic = living parts of the nevironment
    • Tropism (growth response to a stimuli)
      • Phototropism = light
      • Geotropism = gravity
        • shoots have negative geotropism (grown upwards)
      • Hydrotropism = moisture
      • Thigmotropism = touch
      • Chemotropism = chemicals
    • Nastic movement
      • touch sensitive leaves
      • leaves fold rapidly in
        • caused by rapid uptake of water at the base of each leaflet, adjacent cells lose water and collapse
      • cannot be classed as a tropism
      • non-directional responses aka ' nastic movement
        • caused by bio-electrical signals
    • Responses to Herbivory
      • Tannins
        • water soluble flavonoids
        • stored in vacuole and faital to insects
        • bitter taste to herbivores
      • Alkalolds
        • Nitrogenous compounds from amino acids
        • bitter taste or toxic
        • e.g. caffeine or nicotine
        • capsaicin in chillies
      • Pheromones
        • chemical released by a species to affect another organism in the same species
        • ethene released by plants causes ripening of fruit in nearby plants/leaves
        • oxides of ethene are toxic to insects
        • controls chemical defenses

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