Comparative Studies on Physiological and Ecological Characteristics of Solanaceous Fruit Vegetables (8)

The influence of change of various concentration ratios of NO3-N to NH4-N on the plant growth, fruit development and chemical composition of xylem exudate in tomato (cv. Fukuzyu No. 2), eggplant (cv. Hayabusa) and sweet pepper (cv. Shinsakigakemidori) grown in sand culture under glasshouse conditions were investigated.1. Plant growth and fruit development were promoted by the concentration ratio of 7 NO3-N: 3 NH4-N applied in sand culture, but they were inhibited by the high ammonium ratios (0: 10 and 3: 7), especially in tomato. These inhibitions by the high ammonium ratios were reversible by changing the concentration ratios of NO3-N: NH4-N from 0: 10 or 3: 7 to 10: 0 or 7: 3 (0: 10 → 10: 0 or 3: 7 → 7: 3) at early stage (50th day after planting) and conversely growth and fruit development were suppressed by increasing the ammonium nitrogen ratio.2. The increase in ammonium nitrogen ratio resulted in lower exudation rate, followed by the decrease in the concentrations of NO3-N, K, Ca, Mg, Fe, Mn, Cu and Zn and the increase in the amino acids, NH4-N and P in the xylem exudate, especially in tomato plants.3. It may be concluded that growth and fruit development in eggplant and sweet pepper were promoted by application of concentration ratio of 7 NO3-N: 3 NH3-N at every stage, and only in tomato NO3-N nutrition can induce the promotion of fruit development with low incidence of blossom-end rot.