Within and Between Population Variation in Saraca asoca Seed Mass and Shape Affects Seed Germinability

Saraca asoca is a highly traded medicinal tree in India. Due to heavy harvesting of the bark for traditional medicine, the demand for quality planting stock for large-scale plantations to protect the species is high. Medicinal industries and forest departments are popularising this species, but several factors affect its establishment. Being recalcitrant, seeds of the species cannot be stored for long period of time. Hence, available seeds have to be effectively used. Further, significant variations were observed in seeds from different provenances for seed attributes and germination. The present study aimed at understanding the influence of seed morphology on seed germination and seedling vigour of S. asoca seeds collected from three naturally occurring regions in Kerala, Karnataka and Tamil Nadu. Regression analysis showed that roundness was positively correlated with germination (r = 0.433). Synchrony in germination was observed to associate with seed weight (r = 0.613), roundness (r = 0.577), perimeter (r = 0.611) and curve width (r = 0.662). Therefore, roundness could be a reliable trait to identify the seeds’ potential to germinate. Results revealed that smaller and medium-size seeds (Karnataka and Kerala, respectively) produced better seedlings than seeds with maximum seed area from Tamil Nadu. Seedlings raised from small seeds had a vigour index on par with larger seeds. Roundness also revealed better germination synchrony. Therefore, grading should be attempted only within a provenance and not in bulked seed lots.