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Open AccessArticle

Urea Addition Promotes the Metabolism and Utilization of Nitrogen in Cucumber

1
College of Horticulture, Gansu Agricultural University, Anning District, Lanzhou 730070, Gansu, China
2
Institute of Horticulture, Guizhou Academy of Agricultural Science, Xiaohe District, Guiyang 550006, Guizhou, China
3
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; https://doi.org/10.3390/agronomy9050262
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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