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. Dimer. Expressed in roots and rosette leaves. By low oxygen levels but not by cold, dehydration, heat shock, wounding or oxidative stress. Belongs to the plant globin family.