16.5 the commercial use of plant hormones

how are plant hormones used to control ripening

• the gaseous hormone ethene is involved in the ripening of chimacteric fruits (fruits which continue to ripen after they have been harvested)

• after harvesting, these fruits produce ethene which triggers a series of chemical reactions including increased resipitation

• ethene is widely used commerically to generate perfectly ripe fruit for sale for the public

• these fruitd are harvested once fully grown, but long before they are ripe. They are cooled, stores and transported around the world (they are far less likely to be damaged when not ripe). Once they enter the right location for sale, the fruit are exposed to ethene to made them ripen rapidly

hormone rooting powders

• auxins affect the growth of both shoots and roots

• if auxins are powdered and applied to cut shoot, they stimulate production of new roots

• this allows us to propagate new plants from plant cuttings

• the new plants are clones of the parent plant

hormonal weedkillers

• interactions between different plant hormones are finely balanced to enable a plant to grow. If this balance is disrupted that the plant may die.

• This is exactly what we want to do in the case of weeds

• most crops are narrow leaved monocots which most weeds are broad leaves dicots

• the auxins increase the growth rate of the weeks until it is unsustainable and the plant dies

• these synthetic auxins do not affect crop plants or animal species

other uses of auxins

production of seedless fruit

other uses of ethene

• promotes fruit dropping eg. cherries

other uses of cytokinins (useful plant hormone)

• prevent ageing of ripened fruit and vegetables eg. lettuce

• controls tissue development in micropropagation

other uses of gibberellins

• delays ripening and ageing in fruit

• speeds up the malting process in brewing