Summary
Legume roots form nodules housing nitrogen-fixing rhizobia after exchanging signalling molecules.
In depth
Roots release flavonoids; rhizobia respond with Nod factors, causing root hair curling and infection thread formation. Nodule cells become bacteroids that fix nitrogen. Plants get ammonia while bacteria get sugars.
The plant limits nodule number by autoregulation. Leghaemoglobin gives nodules a pink colour and buffers oxygen. Nitrogen fixation costs about 16 ATP per N2, a heavy energy investment.
Example: alder trees use actinobacteria (Frankia) for nitrogen fixation.
Frequently asked questions
What is Root Nodules and Symbiosis?
Legume roots form nodules housing nitrogen-fixing rhizobia after exchanging signalling molecules.
Which area of biology covers Root Nodules and Symbiosis, and how advanced is it?
Root Nodules and Symbiosis is one of the 56 topics in Plant Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Plant Defence Responses, Abscisic Acid and Drought, Mycorrhizal Networks.
Can you give an example of Root Nodules and Symbiosis?
Crop rotation with clover or beans improves soil.
What should I learn before Root Nodules and Symbiosis?
Work through the Beginner topics in Plant Biology first, such as Plant Kingdom, Photosynthesis, Chlorophyll, then return to Root Nodules and Symbiosis. Advanced topics assume the Intermediate vocabulary.
What topics are related to Root Nodules and Symbiosis?
The closest topics to Root Nodules and Symbiosis are Plant Defence Responses, Abscisic Acid and Drought, Mycorrhizal Networks, Stomata. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Root Nodules and Symbiosis?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Root Nodules and Symbiosis. To practise the whole of Plant Biology, use the Plant Biology quiz.
How is Root Nodules and Symbiosis different from Plant Defence Responses?
Root Nodules and Symbiosis: Legume roots form nodules housing nitrogen-fixing rhizobia after exchanging signalling molecules. Plant Defence Responses: Plants use thorns, toxins, jasmonate signalling and systemic acquired resistance against herbivores and pathogens. Read both side by side and note what each one explains.
How should I study Root Nodules and Symbiosis step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Plant Defence Responses and explain the difference aloud. Finally, take the Plant Biology quiz and come back to this page for any question you miss.