In tropical dry forests, fire is a common disturbance and seed traits may drive regeneration of plant populations during these events. In this study, we aimed to (i) investigate whether the seed coat and/or fruit endocarp impose physical dormancy, (ii) check whether physical dormancy confers seed tolerance to heat shocks and (iii) verify whether heat shocks break physical dormancy among woody species. Seeds were collected from five native species of dry forests occurring within the Argentine Chaco: Aspidosperma quebracho-blanco, Sarcomphalus mistol, Schinopsis lorentzii, Prosopis nigra and Vachellia aroma. Initial seed viability was checked by the tetrazolium test before treatments. Heat shocks of 80, 110, 140, and 170 °C simulating a fire event were applied to the seeds for five minutes. Controls consisted of untreated seeds subjected or not to scarification. After heat shock treatments, the seeds were incubated in a germination chamber set at 30 °C under a photoperiod of 12 h (white light). After 35 days, non-germinated seeds were scarified, and after more 55 days the remaining seeds were checked for their final viability. Seed coat does not arrest germination in seeds of A. quebracho-blanco and showed germination after heat shock of 80 °C. Seeds of S. mistol present a fruit wall-imposed dormancy, but barely tolerated heat shock of 80 °C. S. lorentzii present seed dormancy, but not imposed by the seed coat since scarification was ineffective to promote germination; its seeds do not tolerate heat shock. Seeds of P. nigra present endocarp-imposed dormancy, and they germinate after heat shock of 80 °C. Seeds of V. aroma present coat-imposed physical dormancy, and they tolerate heat shock of 80 and 110 °C, but these treatments did not alleviate dormancy. Seed viability among non-germinated seeds after heat shocks were close to zero, revealing a low tolerance to high temperatures. Overall, seed coats did not protect seeds from the damaging effects of heat shock, and heat shock treatments did not break coat- or endocarp-imposed dormancy among the selected species. The heat sensitivity presented by the diaspores suggests that frequent wildfires may reduce their recruitment rates, compromising the maintenance of genetic diversity and the current distribution of their natural populations over the Chaco region.

在热带干旱森林中，火灾是常见的干扰，在这些事件中，种子性状可能会促使植物种群再生。在这项研究中，我们旨在（i）调查种皮和/或果实内果皮是否具有物理休眠，（ii）检查物理休眠是否赋予种子耐热冲击性，以及（iii）验证热冲击是否破坏了木本植物的物理休眠种类。种子采自阿根廷Chaco内的五种干燥森林原生种：Aspidosperma quebracho-blanco，Sarcomphalus mistol，Schinopsis lorentzii，Prosopis nigra和Vachellia香气。在处理前通过四唑鎓测试检查种子的初始活力。将80、110、140和170°C的热冲击模拟起火事件，将其施加在种子上5分钟。对照包括未处理或未进行疏松处理的种子。热激处理后，将种子在设定为30°C的发芽室中于12 h（白光）的光照下孵育。35天后，未发芽的种子被清除，超过55天后，检查剩余种子的最终生存力。种皮不能阻止A. quebracho-blanco种子发芽，在80°C的热冲击后仍显示出发芽。迷雾链霉菌的种子呈现出果实壁施加的休眠，但是几乎不能耐受80℃的热激。洛伦链霉菌目前种子处于休眠状态，但不是种皮强加的，因为稀疏不足以促进发芽；它的种子不能忍受热冲击。黑假单胞菌的种子呈现出内果皮施加的休眠状态，并且在80°C的热冲击下发芽。种子五香味目前，大衣强加了物理休眠，它们可以承受80和110°C的热冲击，但是这些处理并不能缓解休眠。热激后未发芽种子中的种子活力接近于零，这表明其对高温的耐受性较低。总体而言，种皮不能保护种子免受热激的破坏作用，热激处理也不会破坏所选物种中被皮或内果皮造成的休眠。辉绿岩对热的敏感性表明，频繁的野火可能会降低其招募率，从而损害遗传多样性的维护以及查科地区整个自然种群的当前分布。