Alteration in Intra-plant Distribution of δ^<15>N in Response to Shading in Legumes

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    • TATSUMI Jiro
    • Graduate School of Bioagricultural Sciences, Nagoya University


The intra-plant distribution of <SUP>15</SUP>N in common bean, cowpea and soybean having different levels of responses to shading and N<SUB>2</SUB>-fixing ability were analyzed under shaded and non-shaded conditions. Maize was used as a reference (non N<SUB>2</SUB>-fixing) plant. Seedlings were grown in pot soils for 3 weeks then transferred to shaded (55% of control) and non-shaded (control) conditions in a greenhouse, and sampled at 13 days and 24 days after shading. The proportion of plant N derived from N<SUB>2</SUB>-fixation (%Ndfa) estimated by the natural <SUP>15</SUP>N abundance method was higher in cowpea and soybean (74−91%) than in common bean (37−38%). Shade treatment reduced %Ndfa significantly in cowpea and soybean. The difference in δ<SUP>15</SUP>N between shoot and root (Δδ<SUP>15</SUP>N<SUB>s-r</SUB>) was the highest in maize followed by common bean, cowpea and soybean. Shading increased Δδ<SUP>15</SUP>N<SUB>s-r</SUB> in each legume species, particularly in cowpea and soybean. A significant negative correlation was found between Δδ<SUP>15</SUP>N<SUB>s-r</SUB> and %Ndfa in all legumes at both sampling dates (R<SUP>2</SUP> = 0.67−0.96, P<0.1). The slope and Y-intercept of the regression line was similar at the sampling dates, but varied with the species. The slope was −0.05 in cowpea, −0.06 in common bean, and −0.11 in soybean. The Δδ<SUP>15</SUP>N<SUB>s-r</SUB> value estimated by extrapolation of the regression line was 2.9, 2.5 and 8.6‰ at 0 %Ndfa, and −3.2, −2.8 and −2.6‰ at 100 %Ndfa, in common bean, cowpea and soybean, respectively. The consistent relationships between Δδ<SUP>15</SUP>N<SUB>s-r</SUB> and %Ndfa found among legume species suggest that Δδ<SUP>15</SUP>N<SUB>s-r</SUB> could be used as a parameter for estimating %Ndfa without using a reference plant, although the component of regression line was characteristically different among legume species.


  • Plant Production Science

    Plant Production Science 9(3), 219-227, 2006-07-01

    The Crop Science Society of Japan

References:  33


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