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Effect of Ntirogen Concentration in Culture Solution on the Growth and Nutrient Uptake by Rose Plants

Rooted cuttings of rose cv. 'Sonia' were grown in culture solution at various concentrations of nitrogen (N) for about a half year, and the optimal range of N concentration for normal growth, and the relationship between growth and N uptake were investigated. The N concentrations in culture solution were adjusted weekly a 50, 100 or 200 ppm. Plant growth (FW) was determined by weighing weekly the cut flowers, the shoots removed by pruning and defoliated leaves (excised parts), and the other parts, i. e. roots, trunks and old leaves (remaining parts), separately.The plant FW increased with decreasing N concentration in the culture solution. The yield (number and weight) and quality of cut flowers were higher in the solution at low rather than high N concentration. The N uptake per 100 g growth in FW decreased with decreasing the N concentration; plants in 50 ppm N absorbed about 0.7 g N per 100 g growth in FW. Thus, we conclude that for normal growth of rose plants, the N concentration in the nutrient solution should be maintained relatively low.The weight ratio of cut flowers to whole plant in solution at 50 ppm N, where the plant growth and cut flower yield were highest, was 47%. Therefore, to yield 1 kg cut flowers, the plant must increase 2.1 kg in FW and absorb 15 g N.