Effect of Plant Growth Regulators on Seed Germination in Walla Patta (<em>Gyrinops walla</em>)

Abstract

Walla patta (Gyrinops walla Gaertn.) belongs to family Thymelaeaceae, is a valuable endemic plant in Sri Lanka. Recently, this species has become a topic of wide interest due to its ability to produce highly valuable agarwood resin. Commercial cultivation of the species is yet to start, thus natural habitats are tremendously under pressure due to illegal harvest. The seeds of G. walla are recalcitrant and loose the viability within a shorter period of time. Due to the limited availability of information, the present study was aimed at evaluating the effect of plant growth regulators on seed germination. The experiment was conducted in a protected plant house at the Faculty of Agriculture, University of Ruhuna from September 2019 to January 2020. A completely randomized design (CRD) was used with three replicates. The influence of gibberellic acid (GA3), indole-3-acetic acid (IAA), and indol-3-butyric acid (IBA) at 800 ppm, 1000 ppm, and 1200 ppm concentrations on seed germination of the G. walla were investigated. Seeds soaked in nine different hormone solutions for 24 hours were placed in disinfected sand media and germinations were recorded daily up to 60 days. Seeds treated with water served as the control. Final germination percentage, mean germination time, mean daily germination, germination rate index and average time taken to start the germination were recorded. Hormone treatments except IBA at 1000 ppm, significantly increased (p<0.05) the seed germination, when compared with the control. GA3 at 1200 ppm showed the highest (65%) germination followed by IAA at 1000 ppm (53.33%) and 800 ppm (50%). GA3 treatments showed a significantly (p<0.05) faster germination rate than IAA and IBA. Based on the results, GA3 at 1200 ppm can be recommended to enhance the seed germination of G. walla.