Oliveira T G S, Diamantino I P, Garcia Q S
Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Plant Biol (Stuttg). 2017 Sep;19(5):818-823. doi: 10.1111/plb.12597. Epub 2017 Jul 25.
Dormancy cycles are an important mechanism for avoiding seed germination under unfavourable periods for seedling establishment. This mechanism has been scarcely studied in tropical species. Here, we studied three tropical and perennial species of Xyris, X. asperula, X. subsetigera and X. trachyphylla, to investigate in situ longevity and the existence of seasonal seed dormancy cycles. Seeds of three species of Xyris were buried in their natural habitat, with samples exhumed bimonthly for 18 months. Germination of exhumed seeds was assessed under a 12-h photoperiod over a broad range of temperatures. Seeds of X. trachyphylla were also subjected to treatments to overcome secondary dormancy. Seeds of all species are able to form a persistent seed bank and exhibit seasonal changes in germinability. Secondary dormancy was acquired during the rainy summer and was overcome during the subsequent dry season (autumn/winter). Desiccation partially overcomes secondary dormancy in X. trachyphylla seeds. Soil seed bank persistence and synchronisation of seed germination under favourable conditions for seedling establishment contribute to the persistence and regeneration of X. asperula, X. subsetigera and X. trachyphylla in their natural environment.
休眠周期是一种重要机制，可避免种子在不利于幼苗建立的时期萌发。在热带物种中，这一机制鲜有研究。在此，我们研究了三种热带多年生黄眼草属物种，即糙叶黄眼草、亚柄黄眼草和糙叶黄眼草，以调查其种子的原地寿命以及季节性种子休眠周期的存在情况。三种黄眼草属物种的种子被埋在其自然栖息地，每两个月挖掘一次样本，持续18个月。在广泛的温度范围内，在12小时光周期下评估挖掘出的种子的萌发情况。糙叶黄眼草的种子还接受了克服二次休眠的处理。所有物种的种子都能够形成持久的种子库，并表现出萌发能力的季节性变化。二次休眠在多雨的夏季形成，并在随后的旱季（秋季/冬季）被克服。干燥部分克服了糙叶黄眼草种子的二次休眠。土壤种子库的持久性以及在有利于幼苗建立的条件下种子萌发的同步性，有助于糙叶黄眼草、亚柄黄眼草和糙叶黄眼草在其自然环境中的持久性和再生。
