How do shoots respond to gravity and light?
Reveal answer
Negative geotropism, positive phototropism.
Key words: geotropism · phototropism
3(j) CO-ORDINATION AND RESPONSE · RECALL
3.34 Geotropic and phototropic responses
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How do roots respond to gravity?
Reveal answer
Positive geotropism (grow downwards).
Key words: positive
What does a clinostat do?
Reveal answer
Rotates seedlings so gravity (or light) acts equally on all sides.
Key words: rotates
Why does a root on a rotating clinostat grow straight?
Reveal answer
Gravity acts equally all round → no uneven growth → no bending.
Key words: equally
How do you measure a phototropic response?
Reveal answer
Angle of bending with a protractor after a fixed time.
Key words: angle
What is meant by the term phototropism?
Reveal answer
Directional growth response to light.
Key words: phototropism
What is meant by the term geotropism?
Reveal answer
Directional growth response to gravity; also called gravitropism.
Key words: geotropism
What is meant by the term clinostat?
Reveal answer
Device rotating a plant to prevent a constant one-sided gravity stimulus.
Key words: clinostat
Root and shoot tropisms: for Shoot + light, give the response and the growth direction.
Reveal answer
Response: Positive phototropism. Growth direction: Toward light.
Key words: Shoot + light
Root and shoot tropisms: for Root + light, give the response and the growth direction.
Reveal answer
Response: Usually negative phototropism. Growth direction: Away from light.
Key words: Root + light
Root and shoot tropisms: for Root + gravity, give the response and the growth direction.
Reveal answer
Response: Positive geotropism. Growth direction: With gravitational pull.
Key words: Root + gravity
Root and shoot tropisms: for Shoot + gravity, give the response and the growth direction.
Reveal answer
Response: Negative geotropism. Growth direction: Against gravitational pull.
Key words: Shoot + gravity
True or false, and why? “Roots grow down because gravity pulls them like falling objects.”
Reveal answer
False. Gravity is detected and causes differential growth.
True or false, and why? “Shoots are always negatively geotropic and therefore ignore light.”
Reveal answer
False. Several stimuli interact; both responses can influence growth.
True or false, and why? “A clinostat removes gravity.”
Reveal answer
False. It continually changes its direction relative to the organ, reducing a directional response.