EFFECT OF APPLICATION OF GROWTH REGULATORS ON GROWTH AND FLOWER PERFORMANCE OF Jasminum sambac

Jasminum sambac is the oldest commercial flower belonging to the family Oleaceae. The crop has main flowering seasons, i.e. from March to October and an off-season from November to February. However, the seasonal nature of flowering is one of the serious problems that affect both jasmine growers and consumers. In addition to that the maximum and minimum productive seasons, which affect the price trends of jasmine greatly. At present, the use of growth regulators to develop and increase production has received the uttermost attention. In the light of this situation, current study was conducted at the Royal Botanical Gardens, Peradeniya, on the "Effects of application of growth regulators on growth and flower yield of Jasminum sambac (Geta pichcha)” during the years 2021-2022. The experiment was laid out in a Completely Randomized Design (CRD) with seven different treatments and six replications. Six-month-old Jasminum sambac plants were selected for investigation. Three growth regulators, GA3, IAA, and Paclobutrazol, were selected at 150 ppm and 200 ppm intervals. Among the various treatments, application of IAA at 200ppm (T4) recorded the highest plant height (49.08cm & 66.00cm at 60 and 120 DAP respectively), length of primary shoots (35.33cm & 57.50cm at 60 and 120 DAP respectively), number of leaves (23.91 & 44.13 at 60 and 120 DAP respectively), number of secondary shoots (3.51 & 8.08 at 60 and 120 DAP respectively) and length of flower buds (2.33cm). The maximum yield of flower buds per plant (241.00) and the highest number of primary shoots (7.00) were noticed in PBZ 200ppm (T6). Earliness of flowering (22.92 days) was recorded by GA3 at 200ppm (T2). According to the findings of the preceding studies, IAA at 200ppm could be recommended for enhancing growth, and both PBZ at 200ppm and IAA at 200ppm were found effective for enhancing the yield and yield attributes of Jasminum sambac.