Uses of plant hormones (HT ONLY)

Plant growth hormones are used in agriculture and horticulture.
Auxins: used to promote growth in tissue culture.
- Selective weed killers: broad-leaved weeds, such as dandelions, have a larger surface area to absorb more weed killer, which causes uncontrollable growth of some cells and inhibits growth in others, killing the plant.
- Rooting powders: plant cuttings are taken, and the cut end of the stem is dipped in rooting powder and placed into the soil where auxin helps the cutting form roots.
Ethene causes the ripening of fruit by controlling cell division. It is involved in the opening of flowers and dropping of leaves.
- Fruit is often picked before it is ripe to prevent rotting during the long journey to supermarkets, so ethene is sprayed on fruit before arriving so it ripens as it is placed on the shelves.
Gibberellins are involved in plant growth as they initiate seed germination and stem elongation, forming flowers and fruit.
- This can be used to end seed dormancy to trigger germination, promote flowering, or increase the size of fruit.

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