AQA GCSE Using Plant Hormones(Biology)

Using Plant hormones

Humans can use plant hormones to control how plants grow and develop. These hormones are used in farming, gardening, and the food industry to improve plant growth, increase crop yields, and control processes such as fruit ripening.

Auxins

There are 3 commercial uses for auxin.

-Selective weed killers

-Rooting powder

-Tissue culture

Auxin and selective weed killers.

Auxins are used to kill broad-leaved weeds (like dandelions) without killing grasses.

Most of our food crops have narrow leaves.

The weeds with their broad leaves have a larger surface area, so they absorb more of the auxin causing them to overgrow and die.

The narrow leaf food crops cannot absorb as much auxin, so they survive.

Lawn weed killers that remove weeds but leave grass behind.

Farmers spray auxin herbicides (weed killers) to increase crop yields.

Auxin in rooting powders.

Auxins stimulate root growth.

Used for: Plant cuttings

Example: A gardener dips a cutting into rooting powder containing auxin to help it grow roots faster.

1.A knife is used to cut off a leaf or a side stem of a plant.

2. The base of the leaf or side stem is dipped into auxin rooting powder to encourage root growth

3. The leaf or side stem is potted into compost and a root system will develop, allowing for a new plant to grow.

Auxin in tissue culture

Auxins are used to promote growth of plant cells in tissue culture.

This allows:

-cloning plants

-producing large numbers of genetically identical plants quickly

Ethene and ripening of fruit.

Ethene is a plant hormone gas that controls fruit ripening.

Fruit is often picked unripe so it doesn’t spoil during transport and is less easily damaged

Then on arrival at the fruit’s destination ethene is used to control when fruit ripens.

Example:

Bananas transported green then ripened in storage using ethene.

Key idea:

Ripening can be controlled during storage and transport.

Gibberellins

There are three uses for gibberellins

-End seed dormancy

-Promote flowering

-Increase fruit size

Ending seed dormancy and Gibberellins.

Some seeds will not germinate naturally.

Gibberellins can trigger germination

Used by farmers to make seeds grow at the right time.

In brewing process barley seeds are made to germinate by spraying gibberellins onto the seeds. This will cause the conversion of starch in the seed into sugars for fermentation.

Promoting flowering and Gibberellins

Gibberellins can make plants flower earlier or flower in conditions where they normally wouldn’t

Useful for commercial flower production for florists.

Increasing fruit size using Gibberellins.

Gibberellins stimulate cell elongation and bigger fruits

Example:larger grapes.

Biodiversity and weed killers

Using weed killers can:

-kill many plant species

-reduce plant diversity

-reduce habitats for insects and animals

Therefore:Biodiversity may decrease