Influence of Zeatin, Kinetin, and Gibberellic Acid Doses on Growth and Biochemical Responses of Melissa officinalis L. (Lemon Balm) Seedlings

This study aimed to assess the impact of Zeatin, Kinetin, and gibberellic acid biostimulant doses key regulators of plant growth and development on the growth and biochemical properties of Melissa officinalis (lemon balm). Conducted under greenhouse conditions using a Completely Randomized Experimental Design with three replicates, the research measured parameters such as seedling and root lengths, fresh and dry weights of seedlings and roots, total phenolic content, and antioxidant activities (CUPRAC and FRAP). The findings revealed that biostimulant treatments significantly improved growth parameters compared to the control, with the exception of root length. The 200 ppm gibberellic acid treatment yielded the highest fresh and dry weights for both seedlings and roots. For biochemical effects, the highest antioxidant activity was recorded in Zeatin40 treatments, while the greatest phenolic content was observed in Zeatin20, highlighting Zeatin’s effectiveness in enhancing total secondary metabolite content.