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Glutamine Nitrogen and Ammonium Nitrogen Supplied as a Nitrogen Source Is Not Converted into Nitrate Nitrogen of Plant Tissues of Hydroponically Grown Pak-Choi (Brassica chinensis L.)

Authors

  • H.-J. Wang,

    1. Authors Wang, Wu, and Tao are with Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang Univ., Hangzhou 310029 China. Author Miller is with Dept. of Food Science, the Cornell Univ., Ithaca, NY 14853-7201, U.S.A. Author Welch is with US Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853-2901, U.S.A. Author Wang is also with College of Geography and Resource Sciences, Sichuan Normal Univ., Chengdu 610068, China. Direct inquires to author Wu (E-mail: lhwu@zju.edu.cn).
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  • L.-H. Wu,

    1. Authors Wang, Wu, and Tao are with Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang Univ., Hangzhou 310029 China. Author Miller is with Dept. of Food Science, the Cornell Univ., Ithaca, NY 14853-7201, U.S.A. Author Welch is with US Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853-2901, U.S.A. Author Wang is also with College of Geography and Resource Sciences, Sichuan Normal Univ., Chengdu 610068, China. Direct inquires to author Wu (E-mail: lhwu@zju.edu.cn).
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  • Q.-N. Tao,

    1. Authors Wang, Wu, and Tao are with Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang Univ., Hangzhou 310029 China. Author Miller is with Dept. of Food Science, the Cornell Univ., Ithaca, NY 14853-7201, U.S.A. Author Welch is with US Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853-2901, U.S.A. Author Wang is also with College of Geography and Resource Sciences, Sichuan Normal Univ., Chengdu 610068, China. Direct inquires to author Wu (E-mail: lhwu@zju.edu.cn).
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  • D.D. Miller,

    1. Authors Wang, Wu, and Tao are with Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang Univ., Hangzhou 310029 China. Author Miller is with Dept. of Food Science, the Cornell Univ., Ithaca, NY 14853-7201, U.S.A. Author Welch is with US Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853-2901, U.S.A. Author Wang is also with College of Geography and Resource Sciences, Sichuan Normal Univ., Chengdu 610068, China. Direct inquires to author Wu (E-mail: lhwu@zju.edu.cn).
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  • R.M. Welch

    1. Authors Wang, Wu, and Tao are with Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang Univ., Hangzhou 310029 China. Author Miller is with Dept. of Food Science, the Cornell Univ., Ithaca, NY 14853-7201, U.S.A. Author Welch is with US Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853-2901, U.S.A. Author Wang is also with College of Geography and Resource Sciences, Sichuan Normal Univ., Chengdu 610068, China. Direct inquires to author Wu (E-mail: lhwu@zju.edu.cn).
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Abstract

ABSTRACT:  Many vegetables, especially leafy vegetables, accumulate NO3-N in their edible portions. High nitrate levels in vegetables constitute a health hazard, such as cancers and blue baby syndrome. The aim of this study was to determine if (1) ammonium nitrogen (NH+4-N) and glutamine-nitrogen (Gln-N) absorbed by plant roots is converted into nitrate-nitrogen of pak-choi (Brassica chinensis L.) tissues, and (2) if nitrate-nitrogen (NO3-N) accumulation and concentration of pak-choi tissues linearly increase with increasing NO3-N supply when grown in nutrient solution. In experiment 1, 4 different nitrogen treatments (no nitrogen, NH+4-N, Gln-N, and NO3-N) with equal total N concentrations in treatments with added N were applied under sterile nutrient medium culture conditions. In experiment 2, 5 concentrations of N (from 0 to 48 mM), supplied as NO3-N in the nutrient solution, were tested. The results showed that Gln-N and NH+4-N added to the nutrient media were not converted into nitrate-nitrogen of plant tissues. Also, NO3-N accumulation in the pak-choi tissues was the highest when plants were supplied 24 mM NO3-N in the media. The NO3-N concentration in plant tissues was quadratically correlated to the NO3-N concentration supplied in the nutrient solution.

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