Phototropism in plants occurs as a growth response to light, where the plant grows towards the light source, typically the sun. This process is regulated by a plant hormone called auxin. When light shines on one side of a plant, auxin redistributes itself by accumulating more on the shaded side of the plant. This uneven distribution causes the cells on the shaded side to elongate more than those on the lighted side, resulting in the plant bending towards the light. This mechanism helps the plant maximize light absorption for photosynthesis and better growth. Key steps in phototropism include:
- Light perception by photoreceptors (mainly phototropins).
- Redistribution of auxin to the shaded side of the stem.
- Increased cell elongation on the shaded side due to higher auxin concentration.
- Bending of the plant stem or shoot toward the light source.
This type of growth is called positive phototropism, commonly seen in shoots, whereas roots often show negative phototropism by growing away from light.
