¹⁵N acquisition by <i>Sarracenia purpurea</i> pitchers supplied with multiple forms of nitrogen.

<p>Nitrogen was provided to pitcher leaves as ammonium nitrate (¹⁵NH₄¹⁵NO₃), uniformly-labeled (U-) ¹³C-¹⁵N-glycine or U-¹³C-¹⁵N-phenylalanine (IN, U-Gly, and U-Phe, respectively) or in combination (IN+, U-Gly+, U-Phe+, respectively) at Fort Albany, Ontario, Canada (left, panels A, C) and at Tom Swamp, Massachusetts, U S A (right, panels B, D). Uptake was measured after 3 hours (top, panels A, B) and 72 hours (bottom, panels C, D) in a pulse-chase experiment. The total amount of N provided to pitchers at Fort Albany was 0.022 mg, and was 0.101 mg N at Tom Swamp. Pitchers with and without the invertebrate food webs were pooled for these analyses because there were no significant differences in ¹⁵N uptake in the two food-web treatments (Fort Albany F_1,96 = 0.137, <i>P</i> = 0.71; Tom Swamp F_1,94 = 1.68, <i>P</i> = 0.20).