Rate of ¹⁵N  vs. ¹⁴N Incorporation

• ¹⁴NH₄⁺  --> ¹⁵NH₄⁺ had the highest rate of
  ¹⁵N incorporation (ratio slopes ¹⁵N/¹⁴N = 19)
  
• ¹⁴NO₃^-  --> ¹⁵NH₄⁺ had the lowest rate of
  ¹⁵N incorporation (ratio slopes ¹⁵N/¹⁴N = 5)