plant responses

• How do plants respond to their environment?

  Like all living things
• How do plant responses compare to animal responses?

  They are slower and less obvious
• What factors do plants respond to?

  Water, light, gravity, and touch
• Which plant reacts very quickly to stimuli?

  Venus flytrap
• What are the external factors affecting plant responses?

  1. Temperature
  2. Day Length
  3. Light Intensity
  4. Gravity
  5. CO2 Concentration
  6. Water
• What happens to enzyme activity in colder temperatures?

  It is low and growth is minimal
• What occurs if temperatures exceed 40 degrees Celsius?

  Enzymes can become denatured
• What can happen if winter is unusually warm?

  Plants may start to grow and get frost damage
• What does an increase in day length signal to plants?

  To prepare for growth and reproduction
• What does decreasing day length in autumn signal to plants?

  To produce seeds and ripen fruit
• How does light intensity affect photosynthesis?

  More light increases the rate of photosynthesis
• What is the growth direction of plant roots and shoots?

  Roots grow downwards, shoots grow upwards
• Why do roots grow towards gravity?

  To absorb water and minerals
• How does carbon dioxide concentration affect photosynthesis?

  More CO2 increases the rate of photosynthesis
• What happens to a plant if it cannot obtain enough water?

  It wilts and closes its stomata
• How can plants communicate water shortage to neighbors?

  By signaling to close their stomata
• What are the main internal factors that regulate plant growth?

  • Growth regulators (plant hormones)
  • Auxins
  • Gibberellins
  • Cytokinins
  • Ethylene
  • Abscisic acid

  
• What is a tropism?

  A growth change in response to a stimulus
• What is a positive growth response in plants?

  Growth towards the stimulus
• What is phototropism?

  Growth in response to light
• How do shoots respond to light?

  They bend towards the light
• How do roots respond to light?

  They grow away from the light
• What is geotropism?

  Growth in response to gravity
• How do roots respond to gravity?

  They grow towards gravity
• How do shoots respond to gravity?

  They grow against gravity
• What is thigmotropism?

  Growth in response to touch
• How do tendrils of pea plants respond to touch?

  They grow around objects they touch
• What is hydrotropism?

  Growth in response to water
• How do roots respond to water?

  They grow towards water
• How do shoots respond to water?

  They grow away from water
• What is chemotropism?

  Growth in response to chemicals
• How does the pollen tube respond during reproduction?

  It grows towards the ovary

  
• What is a growth regulator?

  A chemical that controls plant growth
• What are the two categories of growth regulators?

  1. Growth Promoters – increase growth
  2. Growth Inhibitors – inhibit growth
• How are plant growth regulators transported?

  Via the vascular system, phloem
• How do plant growth regulators compare to animal hormones?

  Similar in chemical nature and function
• What is the most common natural auxin?

  Indole acetic acid (IAA)
• Where is IAA produced?

  In apical meristems, young leaves, seeds
• What are the effects of auxins?

  Stem elongation, root and shoot growth

  
• How do auxins cause phototropism?

  By diffusing to the shaded side of the shoot