Abiotic Stress

• affect of daylight sensitivity

  photoperiodism - plants sensitive to lack of light

  due to light sensitive pigments, that can absorb different types of light, ratio depends on light levels
• abscission

  less light means lower auxin concentration, so ethene produced

  ethene weakens cell wall in abscission zone (separating layer)

  vascular bundles are then sealed off, fatty deposits to protect site where leaf will fall

  cells may retain more water and swell, other external abiotic factors will then finish process
• preventing freezing

  cytoplasm and vacuole sap contain solutes to lower freezing point

  organic molecules may act as antifreeze, or protect if frozen

  chemicals usually only produced in wintry months
• stomatal closure

  ABA

  if water levels falls, transpiration at risk, ABA produced and binds to receptors on stomatal guard cells