Department of Environmental, Population and Organismic Biology, University of Colorado, 80309-0334, Boulder, CO, USA.
Umeå Plant Science Center, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83, Umeå, Sweden.
Oecologia. 2001 Aug;128(3):305-316. doi: 10.1007/s004420100693. Epub 2001 May 17.
The recently recognized importance of organic nitrogen (ON), particularly amino acids, to plant nutrition in many types of agricultural and natural ecosystems has raised questions about plant-microbe interactions, N availability in soils, and the ecological implications of ON use by plants in the light of climate change and N pollution. In this review we synthesize the recent work on availability and plant uptake of amino acids with classic work on ON in soils. We also discuss recent work on the use of natural abundance levels of (15)N to infer N sources for plants. Reliance on ON is widespread among plants from many ecosystems. Authors have reached this conclusion based on laboratory studies of amino acid uptake by plants in pure culture, amino acid concentrations in soils, plant uptake of isotopically labeled amino acids in the field and in plant-soil microcosms, and from plant natural abundance values of (15)N. The supply of amino acids to plants is determined mainly by the action of soil proteolytic enzymes, interactions between amino acids and the soil matrix, and competition between plants and microbes. Plants generally compete for a minor fraction of the total amino acid flux, but in some cases this forms a significant N resource, especially in ecosystems where microbial biomass undergoes large seasonal fluctuations and contributes labile ON to the soil. A quantitative understanding of ON use by plants is confounded by incomplete data on partitioning of ON between plants, mycorrhizal fungi, and competing soil microbes. Further research is needed to predict the ecological implications of ON use by plants given the influence of climatic change and N pollution.
最近人们认识到有机氮（ON），特别是氨基酸，对许多类型的农业和自然生态系统中植物营养的重要性，这引发了关于植物-微生物相互作用、土壤中 N 的有效性以及植物在气候变化和 N 污染背景下利用 ON 的生态影响的问题。在这篇综述中，我们综合了最近关于氨基酸在土壤中的有效性和植物吸收的研究，以及经典的 ON 在土壤中的研究。我们还讨论了最近关于利用天然（15）N 丰度水平推断植物氮源的工作。许多生态系统中的植物广泛依赖 ON。作者根据实验室研究、土壤中氨基酸浓度、同位素标记氨基酸在田间和植物-土壤微宇宙中的植物吸收、以及植物天然（15）N 丰度值得出了这一结论。氨基酸向植物的供应主要取决于土壤蛋白酶的作用、氨基酸与土壤基质的相互作用以及植物和微生物之间的竞争。植物通常竞争总氨基酸通量的一小部分，但在某些情况下，这形成了一个重要的氮源，尤其是在微生物生物量经历大的季节性波动并向土壤提供不稳定 ON 的生态系统中。由于缺乏关于 ON 在植物、菌根真菌和竞争土壤微生物之间分配的完整数据，对植物利用 ON 的定量理解受到了阻碍。需要进一步研究，以预测植物利用 ON 的生态影响，考虑到气候变化和 N 污染的影响。
