Effect of different ammonium to total nitrogen ratios on vegetative growth and flowering of pot plants of poinsettia (Euphorbia pulcherrima

Poinsettia (Euphorbia pulcherrima) is a potted plant، which its colorful bracts appear in short days. In this experiment، effect of different ammonium to total nitrogen ratios on quantitative and qualitative traits of poinsettia was studied. The experiment was conducted as a complete randomized design with three replicates. The plants were irrigated with water containing of different ammonium to total nitrogen ratios of 0، 0. 05، 0. 1 and 0. 16. At the end of experiment، vegetative traits، fresh and dry weight of shoot and root، chlorophyll index and mineral elements concentration were assessed. Overall study results revealed that quality and quantity characteristics of poinsettia were significantly affected by various ammoniums to total nitrogen ratios. So that، the maximum bract area and leaf area achieved for the ratio 0. 05 meq/l and the minimum achieved for the ratio 0. 16 meq/l. Bract productions in plants delayed and its longevity decreased by ratios higher than 0. 05 meq/l. In addition، effect of treatments on fresh and dry weight of bract، leaf، stem، and root and leaf nitrogen level was significant. According to the results، adjustment of ammonium to total nitrogen in the nutrient solution with ratio of 0. 05 meq/l likely makes improving in the production characteristics of poinsettia.