Effect of pre-sowing seed treatments on germination behaviors of Saraca asoca (Roxb.) Willd

Saraca asoca (Roxb.) Willde. is a globally vulnerable tropical tree species with immense medicinal and aesthetic value. High demand for its bark in pharmacological industry resulted in severe reduction of its population in wild, thus paving way to adulteration. The declining population can only be restored and multiplied through both in situ and ex situ conservation efforts. The seeds of the species were reported with less germination. The present study was therefore an attempt to improve the seed germination of the species with mechanical, water based and chemical based presowing treatments, which significantly improved the germination as compared to no presowing treatments (55%) except with boiling water based treatments (11.6618.33%) which significantly reduced germination. Exposing the plumule by rubbing the seed coat with sand paper and soaking the seeds in hot water (70°C) for 12 h significantly enhanced germination. Chemical based presowing treatments with salicylic acid and thiourea also enhanced germination by 1.67–15% and 13.33–31.66%, respectively over control. Higher the concentration of thiourea improved germination than salicylic acid. Temperature of water and exposure time to water also influenced germination. Increasing the temperature of water from room temperature to 70°C increased germination but further increasing the temperature significantly reduced germination over control. Increasing soaking time by 12–24 h, however reduced germination. In terai region of West Bengal, for faster, higher and smoother germination of S. asoca, adaptation of presowing seed treatment may be recommended especially via soaking the seeds in hot water for 12 h.