Interactions between desiccation and dark nitrogen fixation in tropical Nostoc commune



Colonies of Nostoc commune in tropical Oahu have normally become desiccated and inactive in nitrogen fixation by between noon and 2 p.m. On rehydration, the desiccated colonies fix nitrogen at the same rate in the dark and the light for at least 2 h. When rewetted in the dark, desiccated colonies fix nitrogen at more than twice the rate of non-desiccated colonies taken from the light and placed in the dark. The capacity of desiccated colonies to fix nitrogen in the dark when rehydrated is lost during storage for several months, but is rapidly regained after a short period of moist incubation in the light.

This ability to fix nitrogen on rewetting in the dark is well suited to a tropical climate where rainfall is mainly at night and when metabolic activity during the day is restricted by the rapid onset of desiccation.