Uses of plant hormones

  1. Selective Weedkillers *

    • Although auxins are normally growth-promoting, in high enough concentrations they can cause such rapid growth that plant tissues (e.g. the roots) become distorted and damaged, allowing pathogens to enter the plant

    • Synthetic auxins can be used for this purpose and are applied to plants in concentrations 100 times greater than the natural hormones that are found in plants

    • This treatment is effective against weeds that occur in fields of cereal crops or grass lawns, as grasses are significantly less sensitive to these selective weed killers than broadleaved weeds and so remain behind as the weeds die

  2. Rooting Powder *

    • At low doses, auxins can be used to stimulate cuttings to grow new roots

    • These auxins, present at the correct dosage, are sold commercially in the form of rooting powders

    • The lower end of the cutting is dipped in the powder before being planted in compost and with the correct environmental conditions, roots begin to grow shortly afterwards

    • This technique is often used by florist businesses

  3. Seedless fruit

    • Auxins and gibberellins can be used to make unpollinated flowers develop fruit (in nature, this can only normally occur once a flower has been pollinated and fertilised)

    • This is often used in the production of seedless fruits (e.g. seedless grapes)

    • These are known as parthenocarpic fruits (fruits formed without fertilisation)

  4. Fruit Ripening +

    • Ethene can be used to stimulate fruit to ripen

    • This is often used for fruits that are delicate and soft when they are rupe (e.g. bananas and tomatoes) and that can be easily damaged during transport as a result

    • instead, these fruits can be harvested when unripe (and therefore harder), transported and then ripened artificially using ethene during transport or when they have arrived at their destination