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Open AccessArticle

Urea Addition Promotes the Metabolism and Utilization of Nitrogen in Cucumber

College of Horticulture, Gansu Agricultural University, Anning District, Lanzhou 730070, Gansu, China
Institute of Horticulture, Guizhou Academy of Agricultural Science, Xiaohe District, Guiyang 550006, Guizhou, China
Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 12 Zhongguancun S. St., Beijing 100081, China
Authors to whom correspondence should be addressed.
Agronomy 2019, 9(5), 262;
Received: 25 April 2019 / Revised: 20 May 2019 / Accepted: 21 May 2019 / Published: 23 May 2019
(This article belongs to the Special Issue Nutrition Management of Hydroponic Vegetable Crops)
Nitrogen (N) forms include ammonium [NH4+-N], nitrate [NO3-N], and urea [CO(NH2)2]. Urea is the most common nitrogen fertilizer in agriculture due to its inexpensive price and high N content. Although the reciprocal influence between NO3-N and NH4+-N is well known, CO(NH2)2 interactions with these inorganic N forms have been poorly studied. We studied the effects of different nitrogen forms with equal nitrogen on dry matter, yield, enzyme activity, and gene expression levels in cucumber. NO3-N treatment with equal CO(NH2)2 promoted nitrate reduction, urea utilization, and the GS/GOGAT cycle but reduced the nitrate content. UR-2, NR-2, NR-3, NiR, GOGAT-1-1, and GS-4 were upregulated in response to these changes. NH4+-N treatment with equal CO(NH2)2 promoted nitrogen metabolism and relieved the ammonia toxicity of pure NH4+-N treatment. UR-2, GOGAT-2-2, and GS-4 were upregulated, and GDH-3 was downregulated in response to these changes. Treatment with both NO3-N with added equal CO(NH2)2 and NH4+-N with added equal CO(NH2)2 enhanced the activities of GOGAT, GS, and UR and the amino acid pathway of urea metabolism; manifested higher glutamate, protein, chlorophyll, and nitrogen contents; and improved dry matter weight. A greater proportion of dry matter was distributed to the fruit, generating significantly higher yields. Therefore, the addition of urea to ammonium or nitrate promoted N metabolism and N utilization in cucumber plants, especially treatments with 50% NO3-N + 50% CO(NH2)2, as the recommended nitrogen form in this study. View Full-Text
Keywords: nitrogen forms; cucumber; nitrogen metabolism; gene expression nitrogen forms; cucumber; nitrogen metabolism; gene expression
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MDPI and ACS Style

Ma, C.; Ban, T.; Yu, H.; Li, Q.; Li, X.; Jiang, W.; Xie, J. Urea Addition Promotes the Metabolism and Utilization of Nitrogen in Cucumber. Agronomy 2019, 9, 262.

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