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1. The consumption of steroids has psychological and social impacts. Explain.
2. Discovery of synthetic steroid hormones has changed human life. Comment.
3. Steroids, such as synthetic hormones to avoid pregnancy, are largely banned in Bhutan. Comment.
Function of the plant hormones
Students clicks on the link provided to measure the learning on the plant hormones.
The provided link is on the uses of plant hormones for the commercial purpose.
Commercial Uses
Auxins can be used in the production of seedless fruit.
Ethene can be used to cause fruit to fall.
Cytokinins are used to prevent ripe fruit from ageing, and to control tissue development in micropropagation.
Gibberellins can delay ripening and ageing in fruit, to create larger produce.
Controlling Ripening
Ethene is a gaseous plant hormone important in ripening climacteric fruit.
A climacteric fruit is one which requires a burst of ethene to ripen, triggering a series of greatly increased respiration reactions. This includes bananas, mangos, tomatoes and avocadoes, as well as many other fruits which ripen rapidly after picking.
The effect of ethene can be seen when a ripe banana is put in a bag with green bananas. The ethene in the ripe banana will trigger rapid ripening of the others.
Ethene is used commercially to produce perfectly ripened produce in stores. They are picked when fully formed, but not ripened, and then cooled until after transportation and storage. The harder unripened fruit is easier to transport.
When ready for sale, they are introduced to ethene gas in controlled conditions, ensuring they all ripen at the same rate.
This prevents wastage during transport, and increases shelf life.
Hormone Rooting Powders
Auxin is a plant hormone which causes cell elongation, and therefore growth.
The application of auxin to cut shoots causes growth of new roots. If this is then planted either hydroponically or in an orthodox compost planter then the plant is cloned.
This discovery has made propogation (to create a new plant through asexual/sexual reproduction) much easier for horticulturalists.
This is done on a large scale by agriculturalists, who use micropropagation and rooting powders containing auxin to use the cells from a parent plant to many thousands of clones.
Hormonal Weedkillers
If the fine balance of plant hormones is lost, then the plant will die.
In some cases, people such as gardeners can use this to their advantage.
Synthetic auxins can be sprayed onto unwanted plants, causing an increase in metabolism and as a result rapid growth. This soon becomes unsustainable, and the plant dies.
Synthetic auxins are simple to use and cost effective, have low toxicity to animals, and can be selective.
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