Sugar Water vs Salt Water in Plant Growth

[deleted-777813]

I have a science project due on December 2nd, and I received my consent form and started to experiment. My experiment is about plant growth. More specifically, whether salt water or sugar water grows plants faster. For the experiment I used two organic, and authentic house plants. I also made 10 ounces of both sugar and salt water and used one ounce of each liquid on the plant(s)everyday. After using only two ounces of sugar water on one plant and salt water on the other, I noticed my salt water plant began to cripple. I am giving both plants an equal amount of sunlight each day (about 4-5 hours). Please help me understand what is wrong. Also, what is the best decision in order to move forward with the experiment? Please respond ASAP.

p.s, stan talent, stan loona

- STANLOONA

[probiotics]

Hi, stanloona!

This is a great and interesting project! While the results you are getting might be startling, they are exactly what will happen when you add saltwater to a plant. This is caused by something known as osmosis. Osmosis, put simply, is the movement of a solution from an area of high concentration to an area of low concentration until equilibrium is reached. Normally, plants use osmosis to absorb water from the soil. However, when you use salt water to water a plant, the plant is unable to perform osmosis because the water is too dense. What ends up happening is that water is actually drawn out of the plant, dehydrating it, and causing it to cripple. I hope this makes sense.

Since these are the expected results, I would recommend continuing with your project. Do you have a control plant (regular water)? If not, I would recommend adding one.

thanks, probiotics

[deleted-739703]

Hey Stanloona!

This is a really cool experiment!

probiotics pretty much got it spot on -- osmosis is what allows plants to absorb water from the soil because it moves water (and other substances) from a place of high concentration to low concentration. Plant roots are specially designed to allow osmosis to occur and are very permeable, allowing substances to move freely in and out of the plant. However, the water isn't really too dense for the plant to absorb. What happens when you use saltwater on plants is that the soil suddenly has a much greater salt content than the plant, so in order to even out the plant and the soil, saltwater is absorbed by the plant and freshwater is absorbed from the plant by the soil. This dehydrates the plant.

That may be a little tricky to understand, so you could imagine it like this: two friends each have a bucket of 5 cups of water. One bucket has 5 cups of fresh tap water and the other has 1 cup of salt and 4 cups of water. The friends want the water in their buckets to be more equal, so they each dip a cup into their own bucket and pour it into the other friend's bucket. The bucket that had fresh water now has more salt and less water, and the bucket that had saltwater now has less salt and more water.

In specific amounts, salt is actually necessary for plant life. They get this salt from the soil around them (the same way they get water). However, extreme amounts of salt are not healthy for the plant (just like extreme amounts of salt are not good for humans).

I agree with probiotics that you should continue with the experiment and, if you don't have one, obtain a control plant using just water. Don't give up! Although the crippling plant may seem like "bad" or "failed" results, it's actually a sign that your project is going just as planned

Don't hesitate to ask any more questions!

--Emma

[NehaK6]

Hi Stanloona,

Probiotics and Emma did a great job explaining the concept of osmosis, but if you would like a visual representation of what they're talking about, I would recommend watching the Amoeba Sisters's video on Osmosis ([Link: https://www.youtube.com/watch?v=L-osEc07vMs). It's super informative and gives multiple examples on why saltwater can be dangerous to some organisms, including plants.

Hope this helps with your experiment. And remember, science is all about discovery, so have fun as you learn more about this topic and figure out what happened with your results. Good luck and let us know if you have any more questions!

Neha