Effect of Seed Size on Germination and Seedling Fitness in Four Tropical Rainforest Tree Species

Abstract

Dipterocarpus macrocarpus, Canarium strictum, Beilschmiedia assamica and Ostodes paniculata are important tree species of tropical humid forests of northeast that have significant value for timber and various other uses. Little is known about their germination behaviour particularly in relation to the effect of intra-specific variation in seed-size. The present study describes seed weight, days to germination, seedling viability and seedling growth as affected by seed weight variation for the above-mentioned species. Significant variation was recorded in seed weight for all the studied species (p<0.001). Seed weight was strongly correlated with days to germination (P<0.001). High germination was recorded with increase in seed size for O. paniculata (P<0.01) and D. macrocarpus (p<0.01), though it decreased slightly in heavier seeds for C. strictum and B. assamica (p<0.05). Lighter seeds showed earlier germination, however heavier seeds had higher germination percentage. Effect of seed mass on growth performance of seedlings for all investigated species showed a strong positive correlation. The seed weight significantly affected seedling-growth until 180 days after germination and thereafter the differences were not significant.The study highlights that seed weight plays an important role in rapid germination and early seedling establishment in forest stand.