15N isotope dilution to quantify dinitrogen (N2) fixation associated with Canadian and Brazilian wheat

Publisher Website
Google Scholar
Abstract
Putative dinitrogen (N2) fixation associated with wheat (Triticum aestivum L. emend. Thell) has been studied using acetylene reduction and nonisotopic N-balance techniques. Absolute proof of N2 fixation using 15N2 (gas) or 15N isotope dilution procedures has not been reported. This paper presents the first use of the 15N isotope dilution technique to determine in wheat the percent plant N derived from associated N2 fixation. Although inoculation with either Bacillus polymyxa (C-11-25) or Azospirillum brasilense (ATCC 29145) resulted in no significant increase in total plant N in nine Canadian and one Brazilian wheat varieties, isotopic N data showed that N2 fixation did occur. The amounts of plant N derived from atmosphere, fertilizer, and soil varied. A high degree of plant–bacterial specificity existed. In several instances, the substitution of a single chromosome pair in the wheat regulated the amount of N2 fixed. The agreement between this 15N isotope experiment and two previous nonisotopic experiments suggests that the trait supporting N2 fixation in wheat may be consistently expressed in the varietal lines.

This publication has 3 references indexed in Scilit: