effect of different ammonium to total nitrogen ratios on vegetative growth and flowering of pot plants of poinsettia

poinsettia (euphorbia pulcherrima) is a potted plant, which its colorful bracts appear in short days. in thisexperiment, effect of different ammonium to total nitrogen ratios on quantitative and qualitative traits ofpoinsettia was studied. the experiment was conducted as a complete randomized design with threereplicates. the plants were irrigated with water containing of different ammonium to total nitrogen ratiosof 0, 0.05, 0.1 and 0.16. at the end of experiment, vegetative traits, fresh and dry weight of shoot androot, chlorophyll index and mineral elements concentration were assessed. overall study results revealedthat quality and quantity characteristics of poinsettia were significantly affected by various ammoniumsto total nitrogen ratios. so that, the maximum bract area and leaf area achieved for the ratio 0.05 meq/land the minimum achieved for the ratio 0.16 meq/l. bract productions in plants delayed and its longevitydecreased by ratios higher than 0.05 meq/l. in addition, effect of treatments on fresh and dry weight ofbract, leaf, stem, and root and leaf nitrogen level was significant. according to the results, adjustment ofammonium to total nitrogen in the nutrient solution with ratio of 0.05 meq/l likely makes improving in theproduction characteristics of poinsettia.keywords: ammonium, bract, chlorophyll