TY - JOUR
T1 - Low concentrations of nitrate and ammonium stimulate nodulation and N2 fixation while inhibiting specific nodulation (nodule DW g-1 root dry weight) and specific N2 fixation (N2 fixed g-1 root dry weight) in soybean
AU - Gan, Y.
AU - Stulen, I.
AU - van Keulen, H.
AU - Kuiper, P.J.C.
PY - 2004
Y1 - 2004
N2 - Nitrate N is a major inhibitor of the soybean/Bradyrhizobium symbiosis in legumes and although this inhibition has been studied for many years, as yet no consensus has been reached on the specific and quantitative interactions between nitrate and ammonium supply and N2 fixation. The effect of nitrate and ammonium supply on plant growth, nodulation and N2 fixation capacity during the full growth cycle was investigated in both greenhouse and growth chamber experiments with three soybean genotypes. The results show that a high concentration of mineral N (10 mM), either as nitrate or ammonium or ammonium nitrate significantly suppressed nodule number, nodule dry weight and total N2 fixed per plant of nodulated soybeans. However, lower mineral N concentrations, either 1 mM or 3.75 mM significantly enhanced nodule number, nodule dry weight and total N2 fixed per plant, while specific nodulation (nodule dry weight g-1root DW, SNOD) and specific N2 fixation (total N2 fixed g-1root DW, SNF) were significantly reduced, particularly at the early vegetative growth stage V4, compared to the treatment with N2 fixation as the only N source, in both growth chamber and greenhouse experiments. Therefore, we suggest that SNOD or SNF might be better indicators to express the suppressing effect of mineral N addition on nodule performance and N2 fixed. Our studies also showed that ammonium alone was the more efficient N source than either ammonium nitrate or nitrate for soybean, as it resulted in higher biomass accumulation, nodule dry weight, total N accumulation and total N2 fixed by 23, 20, 18 and 44°respectively, compared to NO3-as the N source
AB - Nitrate N is a major inhibitor of the soybean/Bradyrhizobium symbiosis in legumes and although this inhibition has been studied for many years, as yet no consensus has been reached on the specific and quantitative interactions between nitrate and ammonium supply and N2 fixation. The effect of nitrate and ammonium supply on plant growth, nodulation and N2 fixation capacity during the full growth cycle was investigated in both greenhouse and growth chamber experiments with three soybean genotypes. The results show that a high concentration of mineral N (10 mM), either as nitrate or ammonium or ammonium nitrate significantly suppressed nodule number, nodule dry weight and total N2 fixed per plant of nodulated soybeans. However, lower mineral N concentrations, either 1 mM or 3.75 mM significantly enhanced nodule number, nodule dry weight and total N2 fixed per plant, while specific nodulation (nodule dry weight g-1root DW, SNOD) and specific N2 fixation (total N2 fixed g-1root DW, SNF) were significantly reduced, particularly at the early vegetative growth stage V4, compared to the treatment with N2 fixation as the only N source, in both growth chamber and greenhouse experiments. Therefore, we suggest that SNOD or SNF might be better indicators to express the suppressing effect of mineral N addition on nodule performance and N2 fixed. Our studies also showed that ammonium alone was the more efficient N source than either ammonium nitrate or nitrate for soybean, as it resulted in higher biomass accumulation, nodule dry weight, total N accumulation and total N2 fixed by 23, 20, 18 and 44°respectively, compared to NO3-as the N source
KW - cowpea vigna-unguiculata
KW - max l merr
KW - nitrogen-fixation
KW - white clover
KW - xylem sap
KW - growth
KW - plants
KW - yield
KW - assimilation
KW - nutrition
U2 - 10.1023/B:PLSO.0000016558.32575.17
DO - 10.1023/B:PLSO.0000016558.32575.17
M3 - Article
SN - 0032-079X
VL - 258
SP - 281
EP - 292
JO - Plant and Soil
JF - Plant and Soil
IS - 1
ER -