Effects of different doses of zeatin, kinetin, and gibberellic acid biostimulants on growth and biochemical parameters during the seedling development stage of Istanbul Oregano (Origanum vulgare L. ssp. hirtum)

This research was conducted to determine the effects of different doses of zeatin, kinetin, and gibberellic acid biostimulants, which are plant growth and development regulators, on the growth parameters and some biochemical parameters of Istanbul oregano (Origanum vulgare L. ssp. hirtum). The experiment was carried out in a greenhouse setting according to the "Completely Randomized Experimental Design" with three replications. In the study, seedling and root lengths, seedling and root fresh weights, seedling and root dry weights, chlorophyll a, chlorophyll b, total carotenoid content, total phenolic content, and antioxidant activity (CUPRAC and FRAP) parameters were examined. The results of the study showed that all biostimulants increased the growth and biochemical parameters compared to the control, except for seedling dry weight. The highest plant height was obtained from the 200 ppm dose of gibberellic acid, while the highest values in growth parameters, except for root dry weight, were obtained from the 50 and 100 ppm doses of kinetin. The highest values for chlorophyll a, total chlorophyll, total carotenoid, and FRAP antioxidant activity were found at the 40 ppm dose of zeatin, while the highest values for total phenolics and CUPRAC antioxidant activity were observed at the 100 ppm dose of kinetin.