Auxins

Auxins

Auxins are a type of plant hormone.

• Auxins control the growth rate of plant cells.

• They are made in the tip (meristem) of growing stems.

• Auxins cause cells to elongate (stretch out).

Name the most common auxin

IAA

When will the shoot grow directly upwards?

When the plant is illuminated on all sides:

auxins cause the cells in the shoot to grow at the same rate.

What happens when light shines on one side of the shoot?

• Auxins will accumulate on the shady side of the shoot.

• Cells on the shady side of the shoot will elongate, causing the shoot to bend towards light.

• this is an example of positive phototropism.

What is a clinostat?

A device that slowly and repeatedly rotates, to ensure the roots are evenly exposed to light.