Uses of Plant Hormones
- Plant hormones can be extracted or artificially made and used by gardeners and farmers in horticulture and agriculture to usefully control plant growth to obtain larger yields for example
- The use of auxins, ethene and gibberellins commercially has been very beneficial is helping producing food and plants for decoration
- However the everyday use of hormones as weed killers can have a negative effect on biodiversity; as the growth of unwanted but natural plants such as weeds is inhibited
- Many different species of plants are classed as weeds commercially, but to other organisms they are a food source and potential habitat, so destroying them can have negative effects on other organisms in the ecosystem
Auxins
- Auxins can be used as selective weed killers; negatively affecting the growth of broad-leaved plants which are weeds in comparison to the narrow-leaved grasses and cereals grown as crops for food production (which are desired)
- The growth of weeds is controlled by farmers who don’t want their yields to be smaller as a result of competition between crops and weeds for space and nutrients from the soil
- Selective weedkillers disrupt the growth of weeds only, causing them to die
- However once applied to a crop their spread cannot be controlled, and they could affect other plant species negatively
- If a gardener or farmer wants to easily and cheaply produce lots of clones of a desirable plant, then they can take cuttings of the plant and dip the tips in auxins which are sold as ‘rooting powders’ as they encourage the rapid development of roots
- The same principle as above can be used to clone plants in the lab; auxins in this way are used to promote growth in tissue culture where scrapings of cells can be taken from a desirable plant and used to produce clones in a petri dish that are then planted and allowed to grow in soil
Ethene
- Ethene is used in the food industry to control ripening of fruit during storage and transport
- It is far more effective to transport unripe fruit, as ripe fruit is softer and therefore more easily damaged and spoiled
- The production of ethene can be inhibited to delay ripening of fruits in storage; this can either be achieved directly by adding chemicals that prevent ethene from being produced, or by reacting ethene in the air around fruit with substances that can remove it
- When ripening needs to be encouraged (eg. when fruit is in the supermarket), artificially produced ethene gas can be released to speed up the process
Gibberellins
- Gibberellins can be used to:
- End seed dormancy, as a high concentration of gibberellin promotes seed germination. Gibberellin levels naturally rise after a period of dormancy (exposure to cold and dry conditions) – usually, dormancy ends with an intake of water into the seed and warmer weather
- Promote flowering regardless of the weather conditions the plant is in
- Increase fruit size – higher levels of gibberellin promote the development and growth of fruit
