Plant Growth Responses: Tropisms and the Hormones Behind Them · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

How shoots bend without moving

Science · Organisms & Life Processes · ages 17-18
Name ______________________   Date ____________

  1. A chemical made in the shoot tip tells the shoot how to bend. Which one is it?

    • Chlorophyll
    • Auxin
    • Glucose

  2. A young shoot by a window curves toward the glass. What is this response called?

    • Phototropism
    • Gravitropism
    • Wilting

  3. Phototropism means the plant walks toward the light on tiny roots.

    Circle one:   True   False

  4. You lay a potted plant on its side. By morning the stem points up again. What happened?

    • The roots dragged the pot upright
    • The stem stopped growing for good
    • The stem curved up against gravity

  5. Light shines on the left side of a shoot only, and the shoot bends left. Which side grew faster?

    • Both sides equally
    • The lit left side
    • The shaded right side

  6. Removing a shoot tip stops the bending, and replacing it restores bending. What does this show?

    • Leaves do the sensing, not the tip
    • The tip senses light and signals downward
    • The tip shades the stem from all light

  7. A tiny cap covers a shoot tip while one-sided light hits the stem. Will the shoot bend?

    • Yes, the lit stem senses light itself
    • No, the covered tip cannot sense the light
    • Yes, but it will bend away from the light

  8. A friend claims growers spray weed hormones to make weeds grow faster for easy pulling. What is wrong?

    • Weed hormones check weeds instead of boosting them
    • Auxin works only on roots, never on shoots
    • Sprays slide off, so hormones never work
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Answer key

For grown-ups. Fold this page away before handing over the rest.

How shoots bend without moving W1-mt_q1N7OG2_6j-s1

  1. Auxin · Auxin is made in the tip and directs the uneven growth.
  2. Phototropism · The shoot bends toward light by uneven growth, which is phototropism.
  3. False · Plants cannot walk. They bend by growing longer on one side.
  4. The stem curved up against gravity · Shoots answer gravity by curving upward, which is gravitropism.
  5. The shaded right side · The shaded side stretches more, pushing the tip toward the light.
  6. The tip senses light and signals downward · The tip senses the light and sends a chemical message down the shoot.
  7. No, the covered tip cannot sense the light · Covering just the tip stops the response, so no bending follows.
  8. Weed hormones check weeds instead of boosting them · Growers use those hormones to keep weeds in check, not to boost them.
Worksheet · LightMySky