Science Buddies: "Ask an Expert"

Hello. I am conducting an experiment about whether using hydrogen peroxide (an ingredient found in pesticides) will help or hurt the plant itself when used on its own. People have many different opinions about which is true. I have run into some problems, though, like how many days it will take to have any effect, because I am on my third day of my experiment and still nothing has really happened. I would also like to know how much hydrogen peroxide I should use to get an effect faster. I am currently only using a total of 120 mL of hydrogen peroxide per day, none on lily A, 20 mL on lily B, 40 mL on lily C, and 60 ml on lily D. I use this small an amount per day because I only have so much H2O2, but I can buy more if I need to.

Thank you.

Hi Jacob,

Plants can be pretty sturdy when it comes to resisting environmental pollutants. H2O2 is an oxidizing agent and it will kill bacteria and viruses directly, but its effects on higher organisms like plants can take a lot longer. The changes would appear at the cellular level first and only later might there be some differences in flowering or seeding. When you say nothing has happened what you mean is nothing you SEE with your unaided eyes. If you looked at the plants through a microscope, especially the roots, there might be some visible differences.

So, what should you do? I would get enough H2O2 to water the plants just as you are doing now and continue for as long as you have time. Observe the plants every day and write down what you see. I can't tell you what to expect because I have no idea what it will do. A plant could wilt or the leaves could become paler green. Just make note of anything unusual. Also, take photos every couple of days of the whole plants and also close ups of leaves and flowers (if they have flowers).

At the end of your experiment, take lots of photos (make sure you know which photo goes with which plant!) then carefully loosen the soil around the plants, pull them out and examine and photograph the roots. I suspect that the H2O2 may alter the root and corm structure in some visible way. Take close-ups of the roots and corm so you can do a detailed, side-by-side comparison later. You can replant the lilies in some fresh dirt and enjoy their flowers again later on.

The next time you plan a science project, do the research first to make sure you are asking a question that is answerable. Most of the changes we see in the lab, whether they are in plants or mice occur first at the cellular level. We have to take samples of the cells, stain them and examine them under the microscope. Gross changes may occur eventually or they may not. Also, the organism you choose is important. For example, lichens, those cool green things that grow on tree bark and rocks are very sensitive to environmental pollutants and may have responded more quickly and visibly to H2O2 than your lilies.

Scientists do a lot of reading, thinking, talking to other scientists and planning before they start an experiment. We still make mistakes but we try hard to improve the odds in our favor!

Best wishes,

Sybee