Science Buddies: "Ask an Expert"

My topic is on how the dose and method of application affect the activity of a glyphosate-based weed killer, like Roundup. For this project, it says that I'll need plants with well-define leaves. How many plants do I really need for this experiment? Am I going to need alot?

Heytin45,

Welcome to science buddies and thank you for your question. You will need one plant as a control, one that isn't exposed to the weed-killer. Additionally, you will need one for each experiment configuration. For example, if you were to test 3 solution amounts with 2 ways of application, then you would need 6 plants + 1 control = 7 plants total (at a minimum). If you really wanted to do it right, you should have at least 2 of each (7 * 2 = 14 total)...basically a parallel experiment to ensure results are the same given the same conditions.

Please post back if you have other questions.

Hi there,
Thank you for your response. The experiment says that i need 15 plants, though. And it's just for one trial. If i were to test it twice then am im going to need 30 plants?!

Hi again,

Me and two other group members thought 21 plants will be good enough. Each of us will be working with 7 plants. Instead of using 3 solution amounts and 2 ways of application, we will be using 5 solution amounts for 5 plants, so i guess that's only one way of application? With the remainder of the two plants, one will be a controlled variable and the other one will be an extra for now. Also, i need to find some current experiments/classic experiments based on this project, and i can't find anything online. Do you know of some i can look for? Thank you for your time.