6.16B Describe the commercial uses of auxins, gibberellins and ethene in…

The idea

Plant hormones have many commercial applications in agriculture and horticulture. Auxins are used in selective weedkillers, where high concentrations disrupt growth of broad-leaved weeds, and in rooting powders to encourage cuttings to form roots. Gibberellins are used to promote seed germination, to stimulate fruit and flower formation, and to produce seedless fruit by encouraging fruit growth without fertilisation. Ethene is used to ripen fruit, for example speeding up ripening of tomatoes or bananas during transport and storage. Each use exploits the natural role of the hormone, applied at controlled concentrations to achieve a desired commercial outcome.

What earns the marks

• Auxins are used in weedkillers, where high concentrations disrupt the growth of weeds, and in rooting powders to encourage root formation in cuttings.
• Gibberellins are used to promote seed germination, to stimulate fruit and flower formation, and to produce seedless fruit.
• Ethene is used to ripen fruit, controlling the timing of ripening during transport and storage.
• Each commercial use exploits the natural hormonal role, applied at controlled concentrations to achieve a desired outcome.

Common mistakes and how to put them right

• Mixing up hormones and their uses, for example saying ethene promotes germination.

  Put it right: Gibberellins promote germination, while ethene ripens fruit.

• Thinking rooting powders contain gibberellins.

  Put it right: Rooting powders contain auxins to stimulate root growth.

• Believing seedless fruit is produced by ethene.

  Put it right: Gibberellins are used to produce seedless fruit.

Exam tips

• Match each hormone to its specific commercial use and give a brief reason linked to its natural role.
• Use precise terms such as selective weedkiller, rooting powder, germination and ripening.
• When asked to describe, give the hormone, the use and the effect in one clear sentence.