Peas, beans, and peanuts are all examples of legumes. Legumes are a specific type of plant which possess nodules on their roots, as shown below.
What is the purpose of these nodules?
The purpose of these nodules is to convert atmospheric nitrogen into ammonia.
Hope that helps! ★ If you have further questions about this question or need more help, feel free to comment below or leave me a PM. -UnicornFudge aka Nadia
