Abstract
BackgroundElaeocarpus 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.MethodsRipe 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.ResultsGermination 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).ConclusionBased 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.
Highlights
The results presented here form part of a larger study to assess the causes of the species rarity in nature by understanding the species phenology, mode of dispersion, predation, seed physiology, germination pattern, seedling characteristics and factors debilitating seedling establishment
The objectives of the current work were to: (i) understand the type of dormancy present in the seeds of E. prunifolius by subjecting the seeds to a set of physical and chemical treatments; (ii) test if total germination and germination rate were influenced by seed weight; and (iii) examine if the seedling growth and survival were influenced by seed weight
The mean number of days required for germination of control seeds was 213 ± 5 days (T50 = 174 ± 9 days)
Summary
Studies on germination have emerged as an important tool for conservation of many species. Such studies aid understanding of natural regeneration processes as well as identifying possible causes of species decline, persistence or spread in changing landscapes and their response to global climate change 2000; Gill et al 2013; Tanaka-Oda et al 2017) Such studies enable the development of suitable protocols for species conservation and management. The International Union for Conservation of Nature and Natural Resources (IUCN) have identified 38 Elaeocarpus species under various threat categories. 3 species are critically endangered, 4 endangered, 20 vulnerable, 2 near threatened, 8 conservation dependent and 1 data deficient (IUCN 2017). In India, Iralu and Upadhaya New Zealand Journal of Forestry Science (2018) 48:16
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