Plant Growth Hormones

• What do plant hormones control in plants?

  They control and coordinate a plant's growth and development.
• What are auxins?

  Auxins are plant hormones that accumulate at the tips of shoots and roots.
• How do auxins influence plant growth?

  They influence the rate of cell elongation in plants.
• Where do auxins accumulate in a plant?

  At the tips of shoots and roots.
• What is cell elongation in plants?

  Cell elongation occurs in the cells just behind the tip of the plant.
• What growth responses are auxin-induced growth responsible for?

  Phototropism and gravitropism.
• How do shoots respond to light?

  Shoots are positively phototropic and grow towards light.
• What happens to auxin distribution when a shoot is exposed to light?

  More auxin accumulates on the side that is in more light.
• How does auxin affect the growth of a shoot in light?

  It causes the cells on the shaded side to elongate faster, bending the shoot towards the light.
• How do shoots respond to gravity?

  Shoots are negatively gravitropic and grow away from gravity.
• What occurs when a shoot is growing sideways?

  Auxin produces an unequal distribution, with more auxin on the lower side.
• What effect does auxin have on the lower side of a sideways-growing shoot?

  It causes the lower side to grow faster, bending the shoot upwards.
• How do roots respond to gravity?

  Roots are positively gravitropic and grow towards gravity.
• What happens to auxin distribution in a root growing sideways?

  More auxin accumulates on its lower side.
• How does auxin affect root growth?

  In roots, auxin inhibits growth, causing the cells on the top to elongate faster.
• How do roots respond to light?

  Roots are negatively phototropic and grow away from light.
• What happens when a root is exposed to light?

  More auxin accumulates on the shaded side of the root.
• What effect does auxin have on the shaded side of a root?

  It inhibits cell elongation on the shaded side, causing the root to bend downwards.
• What is a practical way to investigate plant growth responses to light using cress seeds?

  1. Place 10 cress seeds in three Petri dishes with moist filter paper.
  2. Shine light on one dish from above and two from different directions.
  3. Observe the seedlings after one week.
  4. Control variables like temperature and distance from the lamp.
• What should be controlled in the experiment with cress seeds to ensure accurate results?

  Variables such as temperature, distance from the lamp, type of seeds, and number of seeds should be the same.
• What is a part of a plant that is positively gravitropic?

  The root.