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.
These reactions occur in the stroma of the chloroplasts. Most plants use the Calvin (C3) cycle to fix carbon dioxide. C3 refers to the importance of 3-carbon molecules in the cycle. Some plants, known as C4 plants and CAM plants, differ in their initial carbon fixation step.