Ebrahim Alami - Department of Horticultural Sciences, Faculty of crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
Mahnaz Karimi - Department of Horticultural Sciences, Faculty of crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

One of the important objectives during the production cycle of ornamental plants is to regulate and control their growth. Hence, application of some plant growth regulators such as uniconazole (UN) and cycocel (CCC) is considered as an efficient method for reaching to this objective. To investigation the effect of uniconazole and cycocel on some morphological and biochemical characteristics of zinnia, a factorial experiment was conducted in a completely randomized design with five replications. Application of UN (0, 5 and 10 mg L-1) and CCC (0, 1000 and 1500 mg L-1) as growth retardants, was considered as the first and their application method (leaf spraying and soil application) was considered as the second factor. The effect of growth retardants on plant height, Time of flowering, peroxidase activity, endogenous gibberellins and leaf area were significant. The lowest plant height was observed in soil application of 10 mg L-1 UN. The tallest plant was observed in the control treatment. Growth retardants had significant effects on endogenous gibberellins and leaf chlorophyll contents. Highest activity of peroxidase enzyme was detected in plants treated by 10 mg L-1 UN. The highest and lowest numbers of leaves (21.6 and 16.4 leaves, respectively) were counted in control and 5 mg L-1 UN, respectively. According to the obtained results, the use of growth retardants is recommended to reduce the height and improve the qualitative and quantitative characteristics of zinnia flower.

Enzyme activity, gibberellin, ornamental plants, Plant morphology, Growth retardant