Tendrils coil around a support

The idea

Tendrils are sensitive to touch: the part in contact with a support grows less rapidly than the part away from it, so the tendril circles around the support and clings to it.

A pea plant climbs

A pea plant climbs up fences by means of parts called tendrils.

How do you think a tendril curls around a fence?

• The side touching the fence grows less than the side away from it
• The side touching the fence grows faster than the other side
• Muscles in the tendril pull it round

Meet the support

Press Next step to watch what happens to the tendril.

Uneven growth makes a curl

If one side of a thing grows longer than the other, it curves towards the shorter side. That shorter side is the one touching the support.

Tendrils are sensitive to touch. The part in contact with a support grows less rapidly than the part away from it, so the tendril circles around the support and clings to it.

Notes

Tendrils are sensitive to touch: the part in contact with a support grows less rapidly than the part away from it, so the tendril circles around the support and clings to it.

Check yourself

A tendril touches a support. Which part grows less rapidly?

What does the tendril do as a result?

What are tendrils sensitive to?

• The part away from the support. The part away from the support grows more rapidly.
• Both parts grow equally. Because the two sides grow unequally, the tendril circles around the support.
• The part in contact with the support — correct. Yes!
• It circles around the support and clings to it — correct. Yes!
• It grows straight away from the support. Unequal growth makes it circle around the support.
• It folds up and droops like the sensitive plant. That movement involves no growth. A tendril circles because of unequal growth.
• Gravity. Gravity changes the direction of roots and shoots in geotropism. Tendrils are sensitive to touch.
• Touch — correct. Yes!
• Taste. Gustatory receptors in animals detect taste. Tendrils are sensitive to touch.