Maleki Keyvan, Baskin Carol C, Baskin Jerry M, Kiani Mohadeseh, Alahdadi Iraj, Soltani Elias
Department of Agronomy and Plant Breeding Sciences, College of Aburaihan University of Tehran Tehran Iran.
Department of Biology University of Kentucky Lexington Kentucky USA.
Ecol Evol. 2022 Aug 26;12(8):e9240. doi: 10.1002/ece3.9240. eCollection 2022 Aug.
Germination timing is an important determinant of survival and niche breadth of plants. The annual plant occurs in diverse environments along a steep temperature gradient and thus is a suitable model for the study of germination behavior in response to temperature. We used a modeling approach to compare the germination thermal niche of seeds of nine populations of produced in a common garden. Germination time courses were obtained by a newly developed process-based model, and thermal niche was visualized by plotting germination breadth as a function of after-ripening time. Seeds were sampled five times: immature (2 weeks before maturity), mature, and afterripened for 1, 2, and 5 months. Immature and mature seeds had a greater depth of dormancy than afterripened seeds, as estimated by lower values of high-limit temperatures ( ). Afterripening increased germination percentage, synchrony, and thermal niche breadth of all nine populations. The highest asynchrony was for immature and mature seeds, and afterripening enhanced synchrony. Based on the new graphical method, has Type 1 nondeep physiological dormancy, and thus, the germination niche is narrow at seed maturity, leading to a delayed germination strategy that is highly dependent on thermal time accumulated during afterripening. Our findings show that there is considerable variation in the germination thermal niche among populations. Temperature regimes in the natural habitats of have played a significant role in shaping variation in thermal niche breadth for seed germination of this annual species. The models used in our study precisely predict germination behavior and thermal niche under different environmental conditions. The germination synchrony model also can estimate germination pattern and degree of dormancy during the year, suggesting a useful method for quantification of germination strategies.
萌发时间是植物生存和生态位宽度的重要决定因素。这种一年生植物生长在沿陡峭温度梯度的多样环境中，因此是研究温度响应下萌发行为的合适模型。我们采用建模方法比较了在一个共同花园中培育的该植物九个种群种子的萌发热生态位。通过一个新开发的基于过程的模型获得萌发时间进程，并通过绘制萌发宽度作为后熟时间的函数来直观呈现热生态位。种子分五次采样：未成熟（成熟前2周）、成熟以及后熟1个月、2个月和5个月。通过较高极限温度（）的较低值估计，未成熟和成熟种子的休眠深度比后熟种子更深。后熟增加了所有九个种群的萌发率、同步性和热生态位宽度。未成熟和成熟种子的异步性最高，后熟增强了同步性。基于这种新的图形方法，该植物具有1型非深度生理休眠，因此，种子成熟时萌发生态位较窄，导致高度依赖后熟期间积累的热时间的延迟萌发策略。我们的研究结果表明，不同种群间的萌发热生态位存在相当大的差异。该植物自然栖息地的温度状况在塑造这种一年生植物种子萌发热生态位宽度的变异方面发挥了重要作用。我们研究中使用的模型精确预测了不同环境条件下的萌发行为和热生态位。萌发同步性模型还可以估计一年中的萌发模式和休眠程度，这表明它是一种量化萌发策略的有用方法。
