plant response and adaptation to the environment

• Plants


  • Respond to the environment
  • Common plant hormones and how they influence plant physiology
  • Mechanisms by which plants defend themselves
• All living organisms respond to the environment
• Plant responses and adaptations


  • Evolved to suit a stationary life
  • Bending of a seedling/leaves toward light
  • Branching of roots in nutrient-rich soil
  • Herbivore defense

  
• Plant hormones


  • Chemical signals that modify or control physiological (or behavioral) processes
  • Produced in low concentrations, but minute amount can have drastic effects
  • Regulate plant growth by affecting the division, elongation, and differentiation of cells
• Plant hormones


  • Auxin (e.g. indoleacetic acid)
  • Gibberellins
  • Abscisic acid
  • Ethylene
• Auxin


  Promotes shoot elongation and 'bending'; apical dominance
• Gibberellins


  Promote stem elongation, fruit growth, and seed germination
• Abscisic acid


  Seed dormancy, stomatal closure
• Ethylene


  'triple response' in stems, leaf abscission, and fruit ripening
• Many hormones involved in plant defense against pathogens and herbivores
• Auxin: apical dominance


  Ensures that the plant grows taller at the top and branches laterally only at the base
• Plants respond to a variety of stimuli
• Stimuli to which plants respond


  • Light
  • Temperature
  • Mechanical stimuli
  • Chemicals
  • Gravity
• Phototropism


  Growth in response to light
• Plant defenses - pathogens


  • Plants have evolved immune responses against pathogens (viruses, bacteria, fungi)
  • e.g. hypersensitive response: formation of a ring of local cell death around infected site
• Plant defenses - herbivores


  • Herbivore: an animal that feeds on plants
  • Plants have evolved a variety of defenses against herbivores
• Plant defenses against herbivores


  • Mechanical
  • Chemical
  • Biotic
• Mechanical defense


  • Cuticle: dermal tissue
  • Trichomes: leaf "hairs"
  • Spines
• Biotic defense


  • Myrmecophytes: 'ant-plants'
  • Volatiles and tritrophic interactions