effect of paclobutrazol and cycocel on vegetative growth and

abstract growth retardants are new chemical organic compounds that increase period of flowering, leave chlorophyll, lateral shoot number, flower number and decrease vegetative growth. they also increase dry, cold and heat tolerance. paclobutrazol and cycocel are examples of these compounds. this study was conducted to evaluate the effect of paclobutrazol and cycocel on some quantitative and qualitative traits of rudbeckia. plants transplanted at horticulture department farm, college of agriculture, isfahan university of technology. the experiment was conducted based on randomized completed block design with 3 replications. traits were studied included height, leaf and flower number, lateral shoot number, flower diameter, lateral shoot length, leave chlorophyll, the period of flowering , root fresh and dry weight, leaf area, root number, diameter and length, root and shoot carbohydrate. results showed that paclobutrazol 30 ppm reduced leaf number. cycocel 2000 ppm produced the most leave chlorophyll, the period of the flowering and root diameter. paclobutrazol 5 ppm and cycocel 500 ppm reduced flower number. all treatments except cycocel 500 ppm significantly reduced leaf area. there were no significant difference between treatments related to height, lateral shoot number, lateral shoot length, flower diameter, root fresh and dry weight and root and shoot carbohydrate.