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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
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, ie, 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 + 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 affec ted. Only pyruvate