Examkin

Soru

Zorluk: OrtaHormonal Coordination in Plants and Animals

A potted bean seedling placed vertically receives light strictly from one side horizontally. Over 48 hours, the shoot bends toward the light source. What primary physiological mechanism accounts for this differential growth response?

  1. Auxin translocates laterally to the unlit side of the stem, stimulating increased cell elongation on that side.Cevap
  2. B
    Auxin accumulates predominantly on the illuminated side, promoting rapid cell division facing the light.
  3. C
    Auxin breaks down completely on the unlit side, causing cells on that side to contract and pull the stem toward light.
  4. D
    Auxin remains evenly distributed throughout the apex, but light directly hardens cell walls on the shaded side.

Cevap

Auxin translocates laterally to the unlit side of the stem, stimulating increased cell elongation on that side.
The correct answer accurately states that auxin migrates to the unlit (shaded) side of the shoot tip. High concentrations of auxin in stem tissues promote cell elongation, causing the cells on the shaded side to grow longer than those on the lit side, resulting in curvature toward the light.

Adım Adım Çözüm

1
Identify the environmental stimulus and hormone involved
Unilateral light triggers phototropism mediated by indole-3-acetic acid (auxin).
Auxin is the plant growth substance responsible for tropic responses to light and gravity.
2
Determine the direction of hormone movement across the shoot apex
Auxin moves laterally from the illuminated side to the shaded (unlit) side of the shoot.
Light receptors at the shoot tip induce lateral transport of auxin away from the light source.
3
Relate hormone concentration to cellular growth response
Higher auxin concentration on the shaded side causes greater cell elongation, bending the shoot toward light.
In shoot tissues, higher concentrations of auxin promote cell wall loosening and elongation.

Anahtar Kavram

Phototropic response and lateral auxin redistribution in plant shoots
Bu soruyu puanla

Konular

Hormonal Coordination in Plants and Animals

Bu konudan daha fazla soru