Collection, germination and storage of seeds of Saraca asoca (Roxb.) Willd

Abstract

Saraca asoca (Roxb.) Willd. is an important tropical medicinal and ornamental species which has been threatened due to over-exploitation. Developmental changes, germination, and longevity of seeds were studied to ensure better collection, germination and storage of seeds to assist propagation of this species. Seeds were harvested at different developmental stages and fresh and dry mass, moisture content, germination and desiccation tolerance were evaluated to determine the best collection time. Fresh seeds were allowed to germinate at 15–55 °C to find out the optimum temperature for their germination. Seeds were stored to evaluate their longevity at different conditions. During maturation, dry weight of seed reached the maximum at 89 days after anthesis (DAA) after that no change in dry weight was observed till its shedding at 112 DAA. The seeds achieved mass maturity at 89 DAA following a short maturation drying phase. All seeds germinated at 79 DAA when about 64% dry weight was accumulated in seed. They were desiccation sensitive at all stages of maturity, but maximum drying tolerance was achieved 105 DAA onwards. The seeds showed no dormancy. It could germinate at 15–50 °C, and completed germination within 25 days at 30–50 °C. The time required to complete germination increased, if the seeds germinated below 30 °C. Not only temperature, maturity level, and seed moisture content also affected germination period. Storage trials indicated that longevity of seeds could be extended for 4 years at 15 °C, if stored at shedding moisture content. Partially dried mature seeds and immature brownish white seeds collected at 105 DAA also retained viability at 15 °C for 3 years. So, collection can be made a few days before dispersal (105–112 DAA) without much harm to the seed quality. The seeds at this stage of maturity turn brownish white color, a visual indicator of seed collection time.