Multiple environmental cues may break seed physical dormancy (PY) in fire-prone ecosystems, but disentangling the roles of such cues remains challenging. Current research has mostly focused on the role of high temperatures (heat shocks) in PY alleviation, while post-fire environmental conditions are less understood. Here, we examined the role of post-fire temperature fluctuation on seed germination and viability of Cerrado legume shrubs. Specifically, we investigated (1) whether PY is broken by temperature fluctuation; (2) whether seed viability is affected by temperature fluctuations; and (3) micromorphological changes in the seed coat following exposure to temperature fluctuation. Seeds of nine legume species were collected in frequently burned Cerrado savannas. We simulated post-fire temperature fluctuation in germination chambers, with daily temperature fluctuation ranging from 18 to 55 °C for 90 days; controls consisted of untreated seeds (room temperature). We conducted germination trials with unblocked and blocked hilar region of seeds. In addition, seed samples were fixed and subjected to micromorphological analysis. Instead of dormancy break, three species showed decreased seed germination for both unblocked and blocked hilar regions, while other two species showed decreased germination in blocked seeds only. Nevertheless, random cracks formed across the seed coat were found in control and treated seeds, which displayed a proportion of nondormant seeds. Within nondormant seeds, both hilar and extra-hilar regions (such as the pleurogram) may take part on water uptake. Despite the lack of dormancy break, most Cerrado legume seeds persisted viable after post-fire temperature fluctuation, thus avoiding establishment under hazardous conditions. Seed tolerance to heat shocks and post-fire temperature fluctuation likely drives regeneration from seed in burned Cerrado areas.

多种环境提示可能会破坏易火生态系统中的种子物理休眠（PY），但要弄清此类提示的作用仍然具有挑战性。当前的研究主要集中在高温（热冲击）在减轻PY中的作用上，而对火后环境条件的了解却很少。在这里，我们检查了火后温度波动对塞拉多豆科灌木种子萌发和生存能力的作用。具体来说，我们研究（1）PY是否因温度波动而破裂；（2）种子的活力是否受到温度波动的影响；（3）暴露于温度波动后种皮的微观形态变化。在经常燃烧的Cerrado稀树草原中收集了九种豆科植物的种子。我们模拟了发芽室内火灾后的温度波动，每天的温度波动范围是18至55°C，持续90天；对照包括未经处理的种子（室温）。我们对种子的未阻塞和阻塞的肺门区域进行了发芽试验。另外，将种子样品固定并进行微观形态分析。除了休眠中断，三个物种在未阻塞和阻塞的肺门区域均显示出降低的种子发芽，而其他两个物种仅在阻塞的种子中呈现出降低的发芽。但是，在对照和处理过的种子中发现了种皮上形成的随机裂纹，显示出一定数量的非休眠种子。在非休眠的种子内，肺门和肺门外区域（例如胸膜）都可能参与水分吸收。尽管没有休眠中断，火后温度波动后，大多数豆科植物豆科植物种子仍能存活，从而避免在危险条件下定殖。种子对热冲击的耐受性和燃烧后的温度波动可能会推动Cerrado燃烧地区的种子再生。