Effects of partial replacing NO3--N with amino acid on yield, quality and root secretion of pakchoi （Brassica chinensis L. ）
Effects of partial （20%） replacing NO3--N with Gly, Glu and mixed amino acids in the nutrient solution on biomass, quality and root secretion of pakchoi （Brassica chinensis L. ） were studied under the partial sterile hydroponics cultivation. Compared to the single nitrate treatment, the 20% partial replacing NO3--N with amino acids could significantly reduce biomass with decreasing of nitrate and soluble starch content in the edible part of pakchoi after 24 day＇ s treatment. The nitrate and soluble starch contents in the treatment of 20% replacing of NO3--N by Glu are lowest at 1490. 8 mg/kg and 1.77 mg/g, while the contents of soluble protein, soluble sugar, free amino acid and total N in leaves and roots are improved. The treatments of partial replacing NO3--N could change the root morphology structure and root activity, and the contents of NH4＋ -N, free amino acids, total organicC, total N and soluble protein are also significantly increased in the treatments of 20% Gly and 20% of mixed amino acid replacing NO~-N. Compared to the treatment of single nitrate, the ratios of organic nitrogen to total nitrogen in the root secretions are increased by 5.6%, 11.2% and 12. 8% in the treatments of 20% Gly, 20% Glu and 20% of mixed amino acids replacing NO3 -N, respectively. Therefore, partial replacement of NO3 by amino acids could improve the quality of pakchoi, there is a negative relationship between the biomass of pakchoiand the root secretion （0. 7 〈 r 〈0. 83 ,P 〈0. 05 ）, and the types of amino acid could significantly affect biomass, root morphology structure and the amount of root secretion.
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维普
