| environ. |
nitrogen An essential nutrient in the food supply of plants and the diets of animals. Animals obtain it in nitrogen-containing compounds, particularly amino acids. Although the atmosphere is nearly 80% gaseous nitrogen, very few organisms have the ability to use it in this form. The higher plants normally obtain it from the soil after micro-organisms have converted the nitrogen into ammonia or nitrates, which they can then absorb (一种在食品供应的植物和动物饮食中必要的营养物质。动物从含氮的化合物中获得的，特别是氨基酸。虽然空气中差不多80%的是气态氮，但非常少的生物体有能力以这种形式使用它。在微生物体已经把氮转变成之后能被吸收的氨或者硝酸盐后，更高等的植物通常能从土壤中获得它。) |
