For plants inhabiting unpredictable environments, scheduling germination can be challenging. Various responses to environmental conditions have been evolved by plants; these responses combine with variation in local climate to construct germination niche. Germination process may be regulated by a number of factors, among them, the type of seed dormancy and dormancy cycling play an important role in promoting survival after dispersal. In the present study, seeds of Brassica napus were tested for primary conditional dormancy (CD). Dormancy changes were quantified through seed population thermal germination parameters to test whether different genotypes of B. napus seeds (944, 966, Alestrom, Danube, Okanto and Rohan) are non-dormant (ND) at the maturity or if they present primary dormancy (D or CD). In a burial experiment, B. napus seeds dormancy cycling in the natural soil seedbank was investigated. Germination of all genotypes decreased at 5 and > 20°C, showing narrower breadth of thermal niche for germination. Dormancy-breaking treatments lead to the widening of thermal range permissive for germination. The lower limit (T_l(50)) and higher limit (T_h(50)) temperatures for germination decreased and increased, respectively, for non-dormant (after-ripened seeds treated with GA₃) seeds compared with fresh seeds in all genotypes. In fresh seeds, the T_l(50) and T_h(50) for various genotypes ranged from 3.61 to 6.5°C and 25.0 to 29.0°C, respectively and ranged from 0.2 to 1.8°C and 35 to 41.0°C in non-dormant seeds. Thus, fresh seeds of B. napus are dormant at dispersal and adopt delayed germination strategies to avoid summer drought. In the burial experiment, the results indicated that B. napus must have D/ND cycle in which fresh seeds first become dormant and then the cycle begins (CD→D↔CD↔ND), thus adopting both risk-prone and risk-adverse strategies to spread the likelihood of survival over time.

中文翻译：

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甘蓝型油菜种子初休眠及埋藏期休眠变化的定量分析

对于居住在不可预测环境中的植物，安排发芽可能具有挑战性。植物已经进化出对环境条件的各种反应；这些反应与当地气候的变化相结合，构建了发芽生态位。萌发过程可能受多种因素调控，其中，种子休眠的类型和休眠周期对扩散后的存活率起着重要作用。在本研究中，对欧洲油菜种子进行了初级条件休眠 (CD) 测试。通过种子群体热萌发参数量化休眠变化，以测试不同基因型的欧洲油菜种子（944、966、Alestrom、Danube、Okanto 和 Rohan）在成熟时或如果它们呈现初级休眠（D 或 CD）时处于非休眠状态 (ND)。在埋葬实验中，研究了欧洲油菜种子在天然土壤种子库中的休眠循环。所有基因型的发芽在 5°C 和 > 20°C 下均下降，显示发芽的热生态位宽度变窄。打破休眠的处理导致允许发芽的温度范围扩大。对于非休眠（用 GA ₃处理的后熟种子），发芽的下限（T _{l (50)}）和上限（T _{h (50)}）温度分别降低和升高) 种子与所有基因型的新鲜种子相比。在新鲜种子中，各种基因型的T _{l (50)}和T _{h (50)}范围分别为 3.61 至 6.5°C 和 25.0 至 29.0°C，而在非种子中，范围为 0.2 至 1.8°C 和 35 至 41.0°C。 - 休眠种子。因此，欧洲油菜的新鲜种子在传播时处于休眠状态，并采用延迟发芽策略来避免夏季干旱。埋藏实验结果表明，欧洲油菜必须有D/ND循环，其中新鲜种子先休眠，然后开始循环（CD→D↔CD↔ND），因此采用风险倾向和风险不利的方式随着时间的推移传播生存可能性的策略。