Department of Botany, University of Peradeniya, Peradeniya, Sri Lanka.
Postgraduate Institute of Science, University of Peradeniya, Peradeniya, Sri Lanka.
Plant Biol (Stuttg). 2018 Sep;20(5):916-925. doi: 10.1111/plb.12846. Epub 2018 Jun 27.
Fruiting season of many Sri Lankan tropical montane species is not synchronised and may not occur when conditions are favourable for seedling establishment. We hypothesised that species with different fruiting seasons have different seed dormancy mechanisms to synchronise timing of germination with a favourable season for establishment. Using six species with different fruiting seasons, we tested this hypothesis. Germination and imbibition of intact and manually scarified seeds were studied. Effect of GA on germination was examined. Embryo length:seed length (E:S) ratio of freshly matured seeds and of those with a split seed coat was determined. Time taken for radicle and plumule emergence and morphological changes of the embryos were recorded. The radicle emerged from Ardisia missionis, Bheza nitidissima and Gaetnera walkeri seeds within 30 days, whereas it took >30 days in other species. Embryos grew in seeds of B. nitidissima and G. walkeri prior to radicle emergence but not in Microtropis wallichiana, Nothapodytes nimmoniana and Symplocos cochinchinensis. A considerable delay was observed between radicle and plumule emergence in all six species. Warm stratification and/or GA promoted germination of all species. All the tested species have epicotyl dormancy. Seeds of B. nitidissima and G. walkeri have non-deep simple morphophysiological epicotyl dormancy, and the other four species have non-deep physiological epicotyl dormancy. Differences in radicle and epicotyl dormancy promote synchronisation of germination to a favourable time for seedling development. Therefore, information on dormancy-breaking and germination requirements of both radicle and epicotyl are needed to determine the kind of dormancy of a particular species.
许多斯里兰卡热带山地物种的结实期不同，可能不会在有利于幼苗建立的条件下发生。我们假设具有不同结实期的物种具有不同的种子休眠机制，以将萌发时间与有利于建立的季节同步。使用六个具有不同结实期的物种，我们检验了这一假设。研究了完整种子和手动划痕种子的萌发和吸胀。检查了 GA 对萌发的影响。测定了刚成熟种子和种子分裂的种子的胚长度与种子长度（E：S）比。记录了胚根和胚芽的出现时间以及胚胎形态变化。Ardisia missionis、Bheza nitidissima 和 Gaetnera walkeri 的种子的胚根在 30 天内出现，而其他物种则需要超过 30 天。在 B. nitidissima 和 G. walkeri 的种子中，胚在胚根出现之前生长，但在 Microtropis wallichiana、Nothapodytes nimmoniana 和 Symplocos cochinchinensis 中则不然。在所有六种物种中，胚根和胚芽的出现之间都观察到了相当大的延迟。温层积和/或 GA 促进了所有物种的萌发。所有测试的物种都具有上胚轴休眠。B. nitidissima 和 G. walkeri 的种子具有非深简单形态生理上胚轴休眠，而其他四个物种具有非深生理上胚轴休眠。胚根和上胚轴休眠的差异促进了萌发与幼苗发育有利时间的同步。因此，需要了解胚根和上胚轴休眠的打破和萌发要求，以确定特定物种的休眠类型。
