Question

Where are auxins synthesized? How do they promote phototropism?

Answer 1

Step 1: Auxin Synthesis Location:
Auxins originate primarily in the plant's apical meristem, specifically at the shoot and root tips. They are generated in actively growing areas, including stem, leaf, and flower tips. Subsequently, auxins translocate throughout the plant to regulate growth and development.

Step 2: Auxins' Function in Phototropism:
Phototropism is the directional growth of plant organs in response to light. Auxins are central to this process via the following mechanism:
- Unilateral light exposure causes auxins to concentrate on the stem or shoot's shaded side.
- Elevated auxin levels on the shaded side promote greater cell elongation compared to cells on the illuminated side.
- Consequently, the plant bends towards the light source (positive phototropism), optimizing light capture for photosynthesis.

Step 3: Summary:
Auxins, synthesized in the apical meristem, are instrumental in phototropism. Their accumulation on the shaded side of the plant drives differential cell elongation, resulting in the plant's phototropic bending towards light.