Why are healthy root nodules pink in colour?
- Healthy root nodules are pink due to the presence of leghaemoglobin. (like haemoglobin in mammalian blood).
- This leghaemoglobin helps the plant by absorbing oxygen, which inhibit the enzymes in the nodule that 'fix' nitrogen into soluble forms.
- Root nodules without pink colour are likely to be parasitic on the host plant, rather than symbiotic.