May not function as an oxygen storage or transport protein, but might act as an oxygen sensor or play a role in electron transfer, possibly to a bound oxygen molecule. Has an unusually high affinity for O(2) because of a very low dissociation constant. Homodimer. Expressed in coleoptiles, embryos, leaves and roots. By flooding and etiolating but not by oxidative, nitrosative or hormonal stresses. Belongs to the plant globin family.