Effect of nitrogen forms on vegetative growth and flower development at hydroponically grown geraniums (Pelargonium zonale × Pelargonium peltatum)

Nitrogen is an essential macronutrient that greatly influences plant metabolism, growth and development. In plants, nitrogen is taken up in the form of nitrate (NO₃⁻) or ammonium (NH₄⁺), which affect plant physiology, root and shoot growth and the transition to generative phase differently. In this study we investigated the effect of nitrate and ammonium nitrogen forms on growth and development of hydroponically grown geranium plants. Rooted cuttings were cultivated in a floating hydroponic system with four treatments, differing in the nitrate-to-ammonium ratio in the nutrient solution. Treatment with an equal ratio of nitrate and ammonium resulted in greatest increase in shoot and root biomass, together with higher concentrations of chlorophyll a, and ammonium nitrogen in leaves. Treatment with 80:20 ratio (NO₃⁻: NH₄⁺) also had a positive effect on biomass production. Higher nitrate ratios (90%, 100%) promoted higher flowering intensity compared to the 50% nitrate treatment. These findings suggest that a proper ratio of nitrate and ammonium can positively influence growth by increasing shoot and root biomass and enhancing leaf production. The quality of hydroponically grown geraniums can be improved through the optimization of nitrogen form ratios in the nutrient solution.