Seed dormancy, germination and seedling characteristics of Elaeocarpus prunifolius Wall. ex Müll. Berol.: a threatened tree species of north-eastern India

Abstract

Background: Elaeocarpus prunifolius Wall. ex Müll. Berol. is a threatened tree species of north-eastern India. The present study was undertaken to investigate the type of dormancy prevailing in seeds of E. prunifolius, explore seed dormancy breaking techniques and assess seedling fitness. Methods: Ripe fruits of E. prunifolius were harvested from Jaintia hills, and seeds were subjected to various physical, manual and chemical treatments. The effect of plant growth regulators, viz gibberellic acid (GA3) and potassium nitrate (KNO3), were tested. Seedling vigour and survival based on seed weight were examined. Results: Germination took 6 months to initiate after seed dispersal and natural germination percentage of fresh seeds was 24%. Physical pre-germination treatments such as surface and acid scarification failed to overcome dormancy. Cracked seeds promoted germination (46%) with a mean germination time of 146 days (time to 50% germination, T50 = 144 days). Among the GA3 treatments, split seeds treated with GA3 (3000 mg/L−1) yielded the highest germination (24%) with a T50 of 55 days whereas KNO3 did not promote germination. A combination of GA3 and KNO3, however, increased the germination to 31%. Between the seed weight classes, the highest percentage of germination was observed in heavy seeds (25%) and the lowest in light seeds (20%). There was no significant variation between seed weight and germination time (p > 0.05). Seed weight had a significant effect on the shoot height, number of leaves and dry weight of seedlings (p < 0.05). Conclusion: Based on the seed tests, E. prunifolius seeds exhibits ‘combined’ dormancy (physical and physiological) as splitting seed coat and application of GA3 effectively broke dormancy. Splitting the seed coat is a cost-effective method for accelerating germination of seeds. Heavy-weight seeds produced better performing seedlings compared to their counterparts which may be viewed as an important reproductive strategy of the species.