defense in plants

• Physical Defense

  • Dermal covering secretes waxy substance (cutin/cuticle) for water conservation and prevention of attacks
  • Trichomes, barks, spines, and thorns are physical defense structures
• Bacteria and fungi that are beneficial

  • Rhizobium (nitrogen-fixing bacterium)
  • Azospirillium (provide plant growth hormones like gibberellic acid)
• Systematic response to invaders


  Initiates the production of proteinase inhibitor, reminiscent of the immune system
• Production of toxins

  Kill their enemies
• Chemical Defense


  • Secondary metabolites help drive away predators (herbivores)
  • Alkaloids found in plants such as Caffeine, cocaine, nicotine, and morphine
  • Chemical toxins are released to the ground to prevent seed germination
  • Allelopathy helps drive away neighboring trees and results in spacing to minimize shading and overcrowding among plants
  • Cyanides contain cyanogenic glycosides that break down into manihotoxin in cassava
  • Hemlock plant contains neurotoxins that can paralyze and kill a person
  • Castor beans produce a very potent toxin called ricin
• Production and storage of toxins occur in vacuoles