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Asked by to Amelia, Izzy, Sarah on 19 Mar 2014. This question was also asked by .
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Isabel Webb answered on 19 Mar 2014:
Caffeine (the main active chemical in coffee) has an effect on animal brains which perks us up and makes us feel more awake. I think I speak for a lot of scientists when I say we like to drink a lot of it!
Caffeine also has an effect on something other than the brain – calcium. Calcium, which you probably know as being good for healthy bones and teeth, play an important role in cells for other reasons. It is a key signal molecule used to send signals between neighbouring cells. Caffeine triggers plant to release lots of calcium inside themselves. This can have major effects if a lot of caffeine is present.
There is a lot of contrasting evidence out on the internet and a lot of different suggestion. One suggests that too much coffee would mess with the calcium so much that a plant could not germinate. Another says that there is a massive increase in likelihood of mutations that would kill the plant. The changing calcium levels could possibly lead to shorter or strange growing plants that are not healthy.
The only suggestion of coffee helping plants to grow comes from a suggestion that potassium in the coffee is good for plants – potassium is another important signal chemical in cells, so plants need to get it from somewhere – usually fertilisers or just in the soil.
Overall, I’d suggest probably not watering your plants with coffee. It probably messes the calcium signalling up.
Maybe you could suggest an experiment to your science teacher? Grow plants with different amounts of coffee – for example 3 with no coffee, 3 with weak coffee (1/2 teaspoon in a mug of water) and 3 with strong coffee (2 teaspoons in a mug of water). Or even more different variables.
I say do 3 plants of each because real science experiments need to have multiple results showing the same result in order to be properly trustworthy.
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Amelia Frizell-Armitage answered on 20 Mar 2014:
The active chemical in coffee is caffeine. For us when we drink caffeine it has a stimulant effect. This means it can make us feel more awake and able to do things faster than we normally would. However the extent that caffeine effects people like this varies between individuals. Some people only need to drink one cup of coffee to feel super awake, whilst other people have to drink 2 or 3 to get the same effect. Coffee can even make some people feel quite ill.
Plants are basically the same as us. If you water a plant with coffee, or sprinkle a few coffee grounds on the soil every day, you will find that this can help some plants grow faster! However, in some plants caffeine has no effect and grow rate doesn’t change when coffee is added, and like humans, some plants get quite ill when you water them with coffee. The caffeine can stop them growing properly so they grow much slower and end up shorter than normal plants.
As well as direct effect on the plant, if you put your coffee grounds in the soil they will actually break down and add nutrients to the soil. In addition the coffee will attract worms which feed on it. The more worms are in the soil the healthier it is, as worms break down nutrients, and add oxygen to the soil. Both of these things are really good for plant growth.
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anon answered on 20 Mar 2014:
This is the kind of question experimental botanists ask.
I do not know off hand what effect coffee would have on plants….
but it would be interesting to water 2 plants of the same species, one with coffee and one with water for a week and see what happens.
You would then look at what happens, and then look at what we know coffee is made of, and what water does for plants
From here you can attempt to draw conclusions about the effect coffee has on plants!
That’s Science!
If you try this PLEASE let me know!
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