Pedosphere 14(2): 159--164, 2004
ISSN 1002-0160/CN 32-1315/P
©2004 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Tomato growth and organic acid changes in response to partial replacement of NO3--N by NH4+-N
DONG Cai-Xia, SHEN Qi-Rong and WANG Ge
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China). E-mail:
      A hydroponic experiment was conducted to study the efiect of partial replacement of NO3--N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill). A completely randomized design was established with three replications and five treatments, i.e., NO3--N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.
Key Words:  NH4+-N, nitrogen forms, NO3--N, organic acid, tomiato (Lycopersicon esculentum Mill.)
Citation: Dong, C. X., Shen, Q. R. and Wang, G. 2004. Tomato growth and organic acid changes in response to partial replacement of NO3--N by NH4+-N. Pedosphere. 14(2): 159-164.
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