Control and co-ordination in plants

Auxin is produced in the apical meristem of the stem. Production of auxins is affected by sunlight. Light causes auxin to move laterally to the shaded side in the apical meristem. The shaded side will have a higher concentration of auxin than the lighted side. Certain receptors absorb blue light and helps transport auxin to the unlighted side where cells respond by elongating.

When growing plants detect light, auxin synthesised at the root tips, help the cells to grow longer. Also, if light comes from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light