Commercial Uses for Plant Hormones

• Plant hormones can be extracted, or atificial copies can be made. They can then be used to do all kinds of useful things, including killing weeds, growing cuttings and ripening fruit
• Auxins are useful for controlling plant growth:

  • Killing weeds - most weeds growing in fields of crops or in a lawn are broad-leaved, in contrast to grases and cereals which have very narrow leaves. Selective weedkillers have been developed using auxins, which only affect the broad-leaved plants. They totally disrupt their normal growth patterns, which soon kills them, whilst leaving the grass and crops untouched
• Auxins are useful for controlling plant growth:

  • Growing from cuttings with rooting powder - A cutting is part of the plant that has been cut off it, like the end of a branch with a few leaves on it. Normally, is you stick cuttings in the soil they won't grow, but if you add rooting powder, which contains auxins, they'll produce roots rapidly and start growing as new plants. This enables growers to produce lots of clones of a really good plant quickly
• Auxins are useful for controlling plant growth:

  • Growing cells in tissue culture - tissue culture can be used to grow clones of a plant from a few of its cells. To do this, hormones such as auxins need to be added to the growth medium (along with nutrients) to stimulate the cells to divide to form both roots and shoots
• Seed germination is when a seed starts to grow into a plant
• Gibberellin stimulates plant stems to grow
• Gibberellin is a type of plant growth hormone. It stimulates seed germination, stem growth and flowering
• Uses of gibberellin:

  • Controlling dormancy - lots of seeds won't germinate until they've been through certain conditions (e.g. a period of cold or of dryness). This is called dormancy. Seeds can be treated with gibberellin to alter dormancy and make them germinate at times of the year that they wouldn't normally. It also helps to make sure all the seeds in a batch germinate at the same time
• Uses of gibberellin:

  • Inducing flowering - some plants require certain conditions to flower, such as longer days or low temperatures. If these plants are treated with gibberellin, they will flower without any changes in their environment. Gibberellin can also be used to grow bigger flowers
• Uses of gibberellin:

  • Growing larger fruit - seedless varieties of fruit (e.g. seedless grapes) often do not grow as large as seeded fruit. However, if gibberellin is added to these fruits, they will grow larger to match the normal types
• Ethene stimulates ripening of fruit
• Ethene is a gas produced by aging parts of a plant. It influences the growth of the plant by controlling cell division. It also stimulates enzymes that cause fruit to ripen
• Some fruit will produce more ethene as it ripens
• Commercially, it can be used to speed up the ripening of fruits - either while they are still on the plant, or during transport to the shops. This means that fruits can be picked while it's still unripe (and therefore firmer and less easily damaged. The gas is then added to the fruit on the way to the supermarket so that it will be perfect just as it reaches the shelves
• Ripening can also be delayed while the fruit is in storage by adding chemicals that block ethene's effect on the fruit or reduce the amount of ethene that the fruit can produce. Alternatively, some chemicals can be used that react with ethene to remove it from the air