The Physiological impact of some plant growth regulators and spraying dates on the vegetative and root characteristics of myrtle (Myrtus communis L.)

This study was conducted in the lathhouse of the Department of Horticulture and Landscape Design,College of Agriculture,University of Kirkuk,Agricultural Research and Experiment Station at Al-Sayyada,during the period from Sept ,2024,to July 2025.The aim was to investigate the physiological effects of foliar application of different plant growth regulators,namely benzyl adenine(BA),gibberellic acid(GA₃),and indole-3-butyric acid (IBA),each applied at three concentrations(0,100,and 150mg L⁻¹),at two spraying dates:October1(first date)and November1(second date),with two applications for each date, on selected vegetative and floral traits of myrtle(Myrtus communis L.).The experiment was arranged in a Randomized Complete Block Design(R.C.B.D.)using a split-plot arrangement, with three replications and three plants per experimental unit. Data were analyzed using the SAS statistical software, and mean comparisons were performed using Duncan’s Multiple Range Test at the 5%probability level. The results showed that The growth regulators exhibited differential physiological effects. Foliar spraying with IBA at100 mg L⁻¹ significantly increased the number of roots(34.50 roots)and the length of the primary root(35.50 cm).IBA at150mg L⁻¹ significantly enhanced branch length(21.83 cm)and root dry matter percentage(45.83%).GA₃ at100mg L⁻¹ significantly increased total chlorophyll content(134.35 mg g⁻¹),while GA₃at150mg L⁻¹ significantly enhanced leaf number(604.67 leaves plant⁻¹)compared with the control.Spraying dates had a clear impact,with the first date(October1)being significantly superior for all studied traits.At this date,leaf number reached604.81leaves,branch length 21.57cm,total chlorophyll content141.87mg g⁻¹,root number25.04,primary root length31.19cm,and root dry matter percentage74.36%,compared with the second date(November1).The interaction between growth regulators and spraying dates revealed significant effects. Spraying BA at150mg L⁻¹ on the first date significantly increased branch length(27.50 cm).GA₃at150mg L⁻¹ on the first date significantly enhanced leaf number(682.67 leaves plant⁻¹).IBA at100mg L⁻¹ led to a significant increase in root number(36.00roots at the second date and primary root length(36.33 cm at the first date).Moreover, IBA at150mg L⁻¹ significantly increased total chlorophyll content(158.94 mg g⁻¹)and root dry matter percentage(47%).Overall, these treatments outperformed the control in most measured traits.