Marika Doi, K. Higuchi, Akihiro Saito, Takashi Sato, T. Ohyama
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引用次数: 2
摘要
硝态氮在土壤中的浓度是可变的,因此在高硝态氮的土壤中,从根系吸收的氮在缺氮生态位中从茎部再循环到根系。本文以结瘤大豆为材料,研究了15n标记硝酸盐对氮素的吸收、转运和再循环。在5 mM NO3−溶液中,NO3−在根系中积累;而在无氮盆栽中,根系和根瘤中没有检测到NO3−,说明NO3−本身没有从叶片再循环到地下部分。在2 ~ 4 d内,不含氮的对侧半根植株吸收15NO3−的总量比两个半根都吸收NO3−的植株快40%。这一结果可能是由于半根对N需求的补偿可以吸收NO3−。在吸收的15N中,约有2-3%被循环到对面半根,与无N或NO3−溶液无关,这表明从叶片到根系的N循环不受NO3−存在与否的影响。在提供NO3−的半根中,天冬酰胺的浓度增加,而在无N的半根中则没有,这表明天冬酰胺可能不是氮状态的系统信号。
N Absorption, Transport, and Recycling in Nodulated Soybean Plants by Split-Root Experiment Using 15N-Labeled Nitrate
Nitrate concentration is variable in soils, so the absorbed N from roots in a high-nitrate site is recycled from shoots to the root parts in N-poor niche. In this report, the absorption, transport, and recycling of N derived from 15N-labeled nitrate were investigated with split-root systems of nodulated soybean. The NO3− accumulated in the root in 5 mM NO3− solution; however, it was not detected in the roots and nodules in an N-free pot, indicating that NO3− itself is not recycled from leaves to underground parts. The total amount of 15NO3− absorption from 2 to 4 days of the plant with the N-free opposite half-root accelerated by 40% compared with both half-roots that received NO3−. This result might be due to the compensation for the N demand under one half-root could absorb NO3−. About 2–3% of the absorbed 15N was recycled to the opposite half-root, irrespective of N-free or NO3− solution, suggesting that N recycling from leaves to the roots was not affected by the presence or absence of NO3−. Concentrations of asparagine increased in the half-roots supplied with NO3− but not in N-free half-roots, suggesting that asparagine may not be a systemic signal for N status.