[Effects of applying different nitrogen form on cherry tomato nitrogen metabolism during fruit development].

ABSTRACT

A hydroponic experiment was conducted to study the effects of applying 100% NO3- -N, 100% NH4+ -N, and 75% NO3- -N+25% NH4+ -N on the nitrogen metabolism and the nitrate reductase (NR) and glutamine synthetase (GS) gene expression of cherry tomato during its fruit development. Applying 75% NO3- -N+25% NH4+ -N slightly increased the single fruit mass, and increased the fruit NH4+ -N, total amino acid, and total N contents and N accumulation significantly, compared with applying 100% NO3- -N. In treatments 100% NO3- -N and 75% NO3- -N + 25% NH4+ -N, the fruit NR activity and its gene expression had no significant difference, but were higher than those in treatment 100% NH4+ -N. The fruit GS activity was significantly higher in treatment 75% NO3--N+25% NH4+ -N than in treatment 100% NO3- -N. In the three treatments, isozyme GS1 (Cytosolic type GS) and GS2 (Chloroplast type GS) expression was inconsistent with GS activity, suggesting that the effects of applied N on GS activity could be mainly reflected at posttranscriptional level.