Probably the same as any other major... probably even shorter than some (such as pre-med), so 4 years. For my school, you need Intro, Research Methods, Stats, 6 electives and 3 courses from another social science (I chose anthropology, but you can do political science, economics, psychology, etc).
1 Rubisco, the enzyme that is responsible for carbon fixation (combining CO2 with RuBP), can also add O2 to RuBP. 2  When the O2 concentration within a leaf becomes greater than the CO2 concentration, rubisco will add O2 to RuBP instead of CO2.  The resulting molecule cannot be used in the Calvin cycle.
Nitrogenase is an enzyme involved in nitrogen fixation and requires anaerobic conditions. Membranes within root nodules are able to provide these conditions. The rhizobacteria require oxygen to metabolize therefore oxygen is provided by a hemoglobin protein called leghemoglobin which is produced within the nodules.