Journal Article

Weather and nodule mediated variations in δ<sup>13</sup>C and δ<sup>15</sup>N values in field‐grown soybean (<i>Glycine max</i> L.) with special interest in the analyses of xylem fluids

Tadakatsu Yoneyama, Hideshi Fujiwara and Willem M.H.G. Engelaar

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 51, issue 344, pages 559-566
Published in print March 2000 | ISSN: 0022-0957
Published online March 2000 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jexbot/51.344.559
Weather and nodule mediated variations in δ13C and δ15N values in field‐grown soybean (Glycine max L.) with special interest in the analyses of xylem fluids

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The nodulating soybean (Enrei) and its non‐nodulating mutant (EN 1282) were grown in outdoor plots for 2 years (1994: extraordinary dry, high temperature, 1995: ordinary year). Carbon and nitrogen accumulation, δ13C and δ15N values in plant parts and xylem fluids and δ15N values in the water‐extractable soil N were analysed throughout the growing period. Plant growth in 1994 was rapid during the early growth stages, but no pods were produced. In 1995, plant growth was normal and pods were formed. The δ13C values of the leaves were less negative in 1994 than in 1995 and the nodulated plants showed less negative δ13C values than non‐nodulated plants in both years. The δ13C values of the leaves during the vegetative phase were positively correlated to the leaf N concentrations. Leaf N concentrations in their turn were influenced by nodulation and weather conditions and/or soil available N. The δ15N values in the plants and xylem fluids were lower in the nodulated soybean than in non‐nodulated soybean in both years, and estimates of the contribution of N2 fixation in nodulated plants based on plant top δ15N values were 7–14% in 1994 and 37–63% in 1995. The δ13C values of xylem fluids did not differ between nodulated and non‐nodulated plants. Thus, the expected contribution by phosphopenolpyruvate carboxylase‐mediated CO2 fixation in the root nodules to plant C‐incorporation could not have been significant.

Keywords: δ13C; δ15N; nodule CO2 fixation; N2 fixation; soybean.

Journal Article.  4751 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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