Effect of gibberellic acid on some fluorescence and chlorophyll characteristics of Cyclamen persicum Mill. seedlings under different light regimes

The use of growth regulators and light quality change are two methods to improve plant performance. Therefore, a factorial experiment was conducted in a completely randomized design. Factors included three light modes (greenhouse light (control) and LED combination light of white: red: blue as 70: 10: 20 and 40: 40: 20 ratios) and gibberellic acid in four concentrations (0, 20, 40 and 60 mg/l). At the stage of cotyledon emergence, the seedlings were exposed to LED and greenhouse light for 4 months. Gibberellic acid was sprayed on the leaves three times from the end of the third growing month. Based on the results, in the 6- to 8-leaf stage, the highest amount of trapped energy flux (TR0 / RC) was related to greenhouse light and the highest electron transfer flux in each reaction center (ET0 / RC) was observed at the lowest concentration of gibberellic acid (zero) in greenhouse light. The lowest light fluorescence intensity at 50 μs and 2 milliseconds (F0 and Fj) at the lowest gibberellic acid concentration under 40: 40: 20 and the lowest light fluorescence intensity at 60 ms, variable and maximum fluorescence (Fi, FV and Fm) were obtained in the same light regime. The highest content of chlorophyll b and total chlorophyll was obtained in 40: 40: 20 light mode and the highest amount of root fresh and dry weight, root length and volume in the greenhouse and the highest leaf area in the greenhouse and a concentration of 40 mg/l gibberellic acid were observed. Although the use of LED light regimes and high concentrations of gibberellic acid was beneficial in improving some physiological traits and fluorescence indices, in general, natural greenhouse light was sufficient for growing Cyclamen in the seedling production stage.