Details

Autor(en) / Beteiligte

• Sah, R. N.
• Goyal, S. S.
• Rains, D. W.
• Paige, D. F.

Titel

Evaluation of isotopic dilution method for measuring N2 fixation in azolla: comparison with other methods

Ist Teil von

• Journal of plant nutrition, 1989-03, Vol.12 (3), p.341-362

Ort / Verlag

Philadelphia, NJ: Taylor & Francis Group

Erscheinungsjahr

1989

Beschreibungen/Notizen

• An isotopic dilution method that overcomes the drawbacks of commonly used methods for measuring N 2 fixation by aquatic N-fixers such as Azolla pinnata-Anabaena azollae association (Azolla) is presented. The method was compared with 15 N 2 gas (while maintaining CO 2 ) and the difference methods of measuring N 2 fixation. The isotopic dilution method was used for two conditions: a. For 15 N-free growth medium, Azolla was pre-enriched with 15 N, and N 2 fixation was determined by measuring the dilution of 15 N in the tissue. b. For the growth medium containing N, N 2 fixation was determined by providing 15 N enriched ammonium sulfate in the growth medium and measuring 15 N to 14 N ratio in the tissue. An airtight chamber, necessary for 15 N 2 gas and acetylene reduction methods, was not representative of the growing environment of Azolla. Temperature in the airtight chamber was far from uniform and CO 2 was rapidly depleted. The isotopic dilution method is simpler, relatively inexpensive, subject to fewer errors and applicable to more diverse conditions, and yet was as accurate as 15 N 2 -gas method.