Fire is a widespread disturbance that affects plant individuals and populations. In fire-prone environments, such as Mediterranean-type ecosystems, many species are stimulated to germinate by fire-related cues, for example heat and smoke. However, little is known about the effect of fire on seed germination of species from herbaceous communities like temperate grasslands. In this study we assessed the germination response to direct (heat shock and smoke) and indirect (light intensity) fire-related cues of five herbaceous and one shrubby species that occur in natural grasslands of eastern Uruguay. All species are native and belong to the Poaceae (2 species) and Asteraceae (4 species) families. Seeds were subjected to smoke and heat shock treatments (50°C, 100°C) under two light intensities (high-light and low-light). We found that direct fire-related cues did not stimulate germination in any of the species studied. Most of the species showed a reduced percentage of germination or a delayed mean germination time, relative to the control treatment, when exposed to heat shock at 100°C or smoke. However, the seeds survived the exposure to high temperatures, indicating that they can tolerate a fire event. Light was found to be a key germination cue. Treated seeds responded to fire-related cues mainly when we simulated the high-light environment after fire. Our results contribute to the growing body of evidence that many species of South American grasslands do not rely on recruitment by seeds after a fire event, but rather on the ability to resprout by means of subterranean or protected basal buds.

中文翻译：

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光照强度触发温带草原物种对火相关线索的不同发芽反应

火灾是一种影响植物个体和种群的广泛干扰。在容易发生火灾的环境中，例如地中海型生态系统，许多物种受到与火灾相关的线索（例如热量和烟雾）的刺激而发芽。然而，人们对火对温带草原等草本群落物种种子萌发的影响知之甚少。在这项研究中，我们评估了发生在乌拉圭东部天然草原的五种草本和一种灌木物种对直接（热冲击和烟雾）和间接（光强度）火灾相关线索的发芽反应。所有物种都是本地物种，属于禾本科（2 种）和菊科（4 种）。在两种光照强度（高光和低光）下对种子进行烟熏和热休克处理（50°C、100°C）。我们发现直接与火相关的线索不会刺激任何研究物种的发芽。与对照处理相比，当暴露于 100°C 的热激或烟雾时，大多数物种的发芽百分比或平均发芽时间延迟。然而，种子在高温下存活下来，表明它们可以忍受火灾事件。发现光是一个关键的发芽线索。当我们模拟火灾后的高光环境时，处理过的种子主要对与火灾相关的线索做出反应。我们的研究结果有助于越来越多的证据表明，许多南美草原物种不依赖于火灾事件后种子的补充，而是依赖于通过地下或受保护的基芽重新发芽的能力。与对照处理相比，当暴露于 100°C 的热激或烟雾时，大多数物种的发芽百分比或平均发芽时间延迟。然而，种子在高温下存活下来，表明它们可以忍受火灾事件。发现光是一个关键的发芽线索。处理过的种子主要在我们模拟火灾后的高光环境时对与火灾相关的线索做出反应。我们的研究结果有助于越来越多的证据表明，许多南美草原物种不依赖于火灾事件后种子的补充，而是依赖于通过地下或受保护的基芽重新发芽的能力。与对照处理相比，当暴露于 100°C 的热激或烟雾时，大多数物种的发芽百分比或平均发芽时间延迟。然而，种子在高温下存活下来，表明它们可以忍受火灾事件。发现光是一个关键的发芽线索。处理过的种子主要在我们模拟火灾后的高光环境时对与火灾相关的线索做出反应。我们的研究结果有助于越来越多的证据表明，许多南美草原物种不依赖于火灾事件后种子的补充，而是依赖于通过地下或受保护的基芽重新发芽的能力。当暴露于 100°C 的热冲击或烟雾时。然而，种子在高温下存活下来，表明它们可以忍受火灾事件。发现光是一个关键的发芽线索。当我们模拟火灾后的高光环境时，处理过的种子主要对与火灾相关的线索做出反应。我们的研究结果有助于越来越多的证据表明，许多南美草原物种不依赖于火灾事件后种子的补充，而是依赖于通过地下或受保护的基芽重新发芽的能力。当暴露于 100°C 的热冲击或烟雾时。然而，种子在高温下存活下来，表明它们可以忍受火灾事件。发现光是一个关键的发芽线索。当我们模拟火灾后的高光环境时，处理过的种子主要对与火灾相关的线索做出反应。我们的研究结果有助于越来越多的证据表明，许多南美草原物种不依赖于火灾事件后种子的补充，而是依赖于通过地下或受保护的基芽重新发芽的能力。