氮的主要作用首先在于它是生命物质——蛋白质的主要成分，蛋白质含氮16-18%;氮也是核酸的成分;这些都是细胞的重要组成成分。植物的生长发育实际上是细胞的增长，缺少氮元素新细胞就难以形.成，植物的生育就会停滞。所以，氮对根系和枝叶生长表现出明显的影响。

The main function of nitrogen is that it is the main component of protein, which contains 16-18% nitrogen; nitrogen is also a component of nucleic acid; these are important components of cells. The growth and development of plants is actually the growth of cells. Without nitrogen, new cells are difficult to form, and the growth and development of plants will be stagnant. Therefore, nitrogen had a significant effect on the growth of roots and branches.

氮也是叶绿素的重要成分，缺氮时叶绿素形成受阻，使叶片颜色变淡变黄，光合作用减弱甚至停止。氮还是许多酶的成分，没有酶许多代谢过程无法进行。此外，氮也是许多维生素的成分，某些生物碱(如烟碱、茶碱)中也含有氮。

Nitrogen is also an important component of chlorophyll. When nitrogen is deficient, chlorophyll formation is blocked, which makes leaves turn pale and yellow, and photosynthesis weakens or even stops.Nitrogen is also a component of many enzymes, without which many metabolic processes cannot take place.In addition, nitrogen is also a component of many vitamins and is found in certain alkaloids (e.g., nicotine and theophylline).

总之，氮是植物体中许多重要化合物的主要成分。

In a word, nitrogen is the main component of many important compounds in plants.

氮对作物栽培无疑是.重要的。氮素供应适量时，作物生长旺盛，叶子的光合作用功能加强，结实率高，产量高。氮的供应不足;由于蛋白质形成少，导致细胞分裂少，细胞小而壁厚，使之生长缓慢，植株矮小，植株早衰，谷粒不饱满;如是当年缺氮会影响下年果树的萌芽、开花结果。

Nitrogen is undoubtedly the most important for crop cultivation. When the nitrogen supply is appropriate, the crops grow vigorously, the photosynthesis function of leaves is strengthened, the seed setting rate is high, and the yield is high. The lack of nitrogen supply; due to the lack of protein formation, resulting in less cell division, small cells and thick wall, so that it grows slowly, the plant is short, the plant premature senescence, the grain is not full; if the lack of nitrogen in the current year will affect the germination, flowering and fruiting of fruit trees in the next year.

作物缺氮的外观症状各种作物有所差异，但比较一致的表现为：①植株矮小瘦弱，分枝或分蘖短少，花絮小，果小或谷粒不满;②叶小而窄，色淡绿至黄色，首先是老叶或下部叶子出现症状，然后向上部叶片或嫩叶发展;③某些作物(如番茄、烟草等)叶片呈现紫红色。

The appearance symptoms of crop N deficiency are different in different crops, but the most consistent manifestations are: (1) short and emasculated plants, short branches or tillers, small tidbits, small fruits or grain dissatisfaction;(2) small and narrow leaves, pale green to yellow color, the first is the old leaves or lower leaves appear symptoms, and then the upper leaf or young leaf development;Some crops (such as tomatoes, tobacco, etc.) have purple leaves.