In an experiment investigating plant growth responses, an intact coleoptile tip is exposed to directional light coming strictly from the west. After several hours, the coleoptile bends towards the light source. Which physiological mechanism directly accounts for this directional bending?
- Lateral translocation of auxin to the shaded eastern side, causing cell elongation to occur faster on the shaded side than on the lit side.Cevap
- BConcentration of auxin on the illuminated western side, stimulating rapid cell division towards the light source.
- CComplete destruction of auxin on the shaded eastern side, allowing the illuminated side to grow uninhibitedly.
- DSecretion of gibberellins on the illuminated western side, which directly repels the shoot tip away from the shadow.
Cevap
Lateral translocation of auxin to the shaded eastern side, causing cell elongation to occur faster on the shaded side than on the lit side.
Unilateral illumination induces phototropin activation, which promotes the lateral transport of auxin (indole-3-acetic acid) from the lit side to the shaded side of the shoot apex. The elevated auxin concentration on the shaded side stimulates greater cell elongation compared to the illuminated side, causing differential growth that bends the shoot toward the light.
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Phototropism and Auxin Redistribution
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