Impact of Growth Regulators and Light Intensity on the Yield and Steviol Glycosides Content of Stevia (Stevia rebaudiana Bertoni)

The field experiment was conducted at the agricultural research station of the College of Agricultural Engineering Sciences, University of Baghdad, during the 2022 growing season. The study aimed to assess the impact of growth regulators, including Gibberellin (GA3) and Goltar Super (Paclobutrazol 25%), on the growth and yield of Stevia rebaudiana Bertoni, with an emphasis on leaf production and sweetness content. The experiment was conducted under two light - intensity conditions to evaluate the plant's response to these variables. The results revealed that plants attained their maximum height under E2 (92.67 cm); in contrast, plants cultivated in open field conditions demonstrated superior performance in terms of dry weight, leaf weight, and overall yield, registering 171.1 g, 101.7 g per plant, and 6.77 tons per hectare, respectively. Furthermore, plants treated with GA3 at 400 mg L-1 and 200 mg L-1 exhibited the greatest heights, reaching 87.85 cm and 84.83 cm, respectively. The highest dry weight (172.0 g) was recorded in plants treated with GA3 at 200 mg L-1, while the maximum leaf weight and yield were observed with Goltar at 1000 mg L-1 (88.6 g per plant and 5.89 tons per hectare) and GA3 at 200 mg L-1 (87.7 g per plant and 5.83 tons per hectare), respectively. However, none of the treatments led to significant differences in the percentages of Sativoside or Rebaudioside.