Plant Hormones + Their Uses

What are the three plant hormones studied at GCSE?

Auxins, gibberellins and ethene.

What is the main function of auxins?

To control plant growth responses, including cell elongation.

What is the main function of gibberellins?

To stimulate seed germination, stem growth and flowering in certain plants.

What is the main function of ethene?

To control fruit ripening.

What is ethene?

A gaseous plant hormone involved in fruit ripening.

How are auxins used as selective weedkillers?

They cause uncontrolled growth in certain weeds, killing them while leaving many grasses relatively unaffected.

Why are selective weedkillers useful?

They can kill broad-leaved weeds without killing the grass or cereal crop.

How are auxins used in rooting powders?

They stimulate root formation in plant cuttings.

Why are rooting powders useful?

They increase the chance of successful root development in cuttings.

How can auxins be used in tissue culture?

They help control cell growth and root formation.

What is plant tissue culture?

Growing new plants from small groups of plant cells or tissues under controlled conditions.

Why is tissue culture useful?

It allows many genetically identical plants to be produced quickly.

How are gibberellins used in agriculture?

To end seed dormancy, promote germination, increase fruit size and stimulate flowering.

What is seed dormancy?

A state in which a viable seed does not germinate despite some suitable conditions.

How can gibberellins affect seed dormancy?

They can break dormancy and stimulate germination.

How can gibberellins affect fruit growth?

They can increase fruit size in some crops.

How can gibberellins affect flowering?

They can promote flowering in certain plants.

How is ethene used commercially?

To control the ripening of fruit during storage and transport.

Why might fruit be picked before it is fully ripe?

To reduce damage and spoilage during transport.

How can ethene be used after transport?

It can be applied to stimulate more uniform fruit ripening.

Why is controlling fruit ripening economically useful?

It helps reduce waste and manage when fruit is ready for sale.

What is one disadvantage of using plant hormones commercially?

Incorrect concentrations or timing can cause undesirable growth or ripening effects.

Why must plant hormones be used carefully?

Their effects depend on concentration, plant species and developmental stage.