Role of Melatonin and Lighting Conditions in Improving the Growth Traits of Gardenia jasminoides Ellis Cultured in Vitro

• Khitam Falih Abdulhassan & Mohammed J.H. Al-shareefi

  Author

This study was conducted at the Plant Tissue Culture Laboratory, Department of Horticulture and Landscape Gardening, College of Agriculture, Al-Qasim Green University, Iraq, from September 2025 to June 2026 to evaluate the effects of lighting conditions and melatonin concentrations on the growth characteristics of Gardenia jasminoides shoots cultured in vitro. The experiment consisted of two factors with ten replicates: three lighting conditions (white fluorescent, blue LED, and combined red–blue LED) and four melatonin concentrations (0, 0.6, 0.8, and 1.0 mg L⁻¹). Melatonin significantly improved most of the studied growth characteristics; 1.0 mg L⁻¹ produced the highest shoot length, shoot number, and leaf number, whereas 0.8 mg L⁻¹ resulted in the highest dry matter percentage and 0.6 mg L⁻¹ gave the highest chlorophyll content. Lighting conditions also significantly affected plant growth, with the combined red–blue LED treatment producing the highest shoot length, shoot number, leaf number, and dry matter percentage, while red LED light alone resulted in the highest chlorophyll content. Significant interaction effects were observed between melatonin and lighting conditions for all growth characteristics. The combination of 1.0 mg L⁻¹ melatonin with red–blue LED light produced the highest shoot length, shoot number, and leaf number, whereas 0.8 mg L⁻¹ melatonin combined with red–blue LED light resulted in the highest dry matter percentage, and 0.6 mg L⁻¹ melatonin combined with red LED light produced the highest chlorophyll content compared with the control.

• pdf