Assimilation of¹⁵N₂and¹⁵NO₃⁻by Partially Nitrate-Tolerant Nodulation Mutants of Soybean

Photoassimilate partitioning in hypernodulation mutant of soybean (Glycine max(L.) Merr.) NOD1-3 and its parent williams in relation to nitrate inhibition of nodule growth

“…1), as previously reported (Gremaud and Harper 1989;Ohyama et al 1993;Sato et al 1999). As for the individual nodule growth under the 0 mM nitrate conditions, the average nodule size in NODI-3 and Williams was about 2.0 and 2.2 mm at 14 DAP, respectively, and the difference increased to 2.6 (NODI-3) and 3.0 mm (Williams) at 18 DAP (Fig.…”

“…For example, plant growth at the early growth stage is less vigorous than that of the parents. Especially, root growth in the mutant is much less vigorous than that of the parents (Gremaud and Harper 1989;Ohyama et al 1993;Sato et al 1999). This phenomenon can be ascribed to the very strong competition for carbon sources between roots and nodules.…”

“…However, the less vigorous root growth may not be totally due to competition for carbohydrates by excess nodulation, because the root growth of non-inoculated mutant without nodules was still less vigorous than that of the parent (Gremaud and Harper 1989). Secondly, the mutant shows a low nitrate absorption activity (Ohyama et al 1993), although the nitrate reductase activity in the roots was similar (Gremaud and Harper 1989). The restricted growth of the mutant line by nitrate may be related to the defective nitrate absorption traits of the mutant lines.…”

Nitrogen Utilization in the Supernodulating Soybean Variety “Sakukei 4” and Its Parental Varieties,“Enrei” and “Tamahomare”

“…In the preliminary experiment, the yield of Sakukei 4 was the same as that of Enrei in a green house (data not shown), and in our previous fi eld experiment (Shimamura et al, 2007), it was also almost the same as that of Enrei but was lower than that of Tamahomare. Additionally, although the growth and yield of supernodulating soybeans are generally inferior to the normally nodulating ones (Song et al, 1988;Wu and Harper, 1991;Ohyama et al, 1993;Pracht et al, 1994;Song et al, 1995), the yield of Sakukei 4 was the same as that of the normally nodulating varieties, Enrei and Tamahomare.…”

“…Supernodulation is one way of enhancing N 2 fi xation capability, and several supernodulating soybean lines have been isolated (Carroll et al, 1985a, b;Gremaud and Harper, 1989;Akao and Kouchi, 1992). However, most supernodulating lines are inferior to their normally nodulating parental varieties in growth and yield, and have no agronomical benefi t (Song et al, 1988;Wu and Harper, 1991;Ohyama et al, 1993;Pracht et al, 1994;Song et al, 1995).…”