Seed dormancy and germination in Gymnocladus assamicus: An endemic legume tree from Northeast India

Gymnocladus assamicus Kanj. ex P.C. Kanjilal (Caesalpinoideae) is a critically endangered tree species and endemic to northeast India. Several extrinsic and intrinsic regeneration constraints have been identified in the species of which seed-coat imposed dormancy was found crucial. Seeds have an extremely hard and water impermeable testa. Electron microscopic observation revealed densely cuticulated seed surface in G. assamicus. Freshly collected mature seeds showed very high viability percentage (90%) through TTZ test. Orthodox type of seeds retains 11.35% moisture at the end of one year under normal storage condition. Mechanical scarification and hot water treatment showed significant improvement in germination percentage and was found most suitable for breaking seed coat imposed dormancy of the species.