Departamento de Botânica, Universidade de Brasília/Brasil.
Brazilian Corporation of Agricultural Research/Embrapa, Brasília, Brazil.
Am J Bot. 2019 Sep;106(9):1190-1201. doi: 10.1002/ajb2.1345. Epub 2019 Aug 26.
Although fire cues (high temperatures and smoke) influence seed germination in numerous species from fire-prone environments, their effects on seed germination of species from neotropical savannas are poorly understood.
We exposed seeds of eight grass species from the Cerrado, the Brazilian savanna to heat-shock (80°C or 110°C for 5 min) and/or smoke water, and then set them to germinate in light or dark, at either summer (28°C/18°C) or winter (27°C/14°C) temperature regimes in an incubator. In addition, we evaluated the effects of smoke water on seedling root and shoot growth for four of the species.
Smoke interacted with the dark treatment to increase germination from 28% to 93% in Aristida recurvata and 77% to 95% in Aristida riparia. Smoke had no effect on germination of either of these species in the light. Heat-shock alone also promoted seed germination in A. recurvata. For Digitaria lehmanniana, smoke interacted with heat-shock to improve germination from 5% to 16%. In contrast, the fire treatments did not have any effect on the seed germination of the remaining five species. Smoke water stimulated root growth for A. riparia, A. recurvata, and Ctenium cirrosum but had no effect on their shoot growth.
The strong promotive effect of smoke on Aristida germination suggests that these species are fire-adapted. Aristida species have an active awn system, which facilitates seed burial, and the smoke and dark interaction would ensure buried seeds germinated post-fire. The species that showed no response to fire cues may either have adapted via alternative strategies or require different concentrations of smoke or levels of heat. This study is one of very few examples showing a positive germination and seedling growth response to smoke for species from neotropical savannas.
尽管火刺激物（高温和烟雾）会影响来自易发生火灾环境的众多物种的种子萌发，但它们对来自新热带草原的物种的种子萌发的影响还知之甚少。
我们将来自巴西塞拉多草原的 8 种草种的种子暴露于热冲击（80°C 或 110°C 持续 5 分钟）和/或烟雾水中，然后将它们在光照或黑暗下在培养箱中于夏季（28°C/18°C）或冬季（27°C/14°C）温度条件下进行萌发。此外，我们还评估了烟雾水对其中 4 个物种的幼苗根和芽生长的影响。
烟雾与黑暗处理相互作用，使 Aristida recurvata 的萌发率从 28%提高到 93%，Aristida riparia 的萌发率从 77%提高到 95%。在光照下，烟雾对这两个物种的萌发均没有影响。单独的热冲击也促进了 A. recurvata 的种子萌发。对于 Digitaria lehmanniana，烟雾与热冲击相互作用，使萌发率从 5%提高到 16%。相比之下，这些处理对其余 5 个物种的种子萌发没有任何影响。烟雾水刺激了 A. riparia、A. recurvata 和 Ctenium cirrosum 的根生长，但对其芽生长没有影响。
烟雾对 Aristida 萌发的强烈促进作用表明这些物种具有适应火灾的能力。Aristida 物种具有活跃的芒系统，这有助于种子的埋藏，而烟雾和黑暗的相互作用将确保火灾后埋藏的种子萌发。对火灾信号没有反应的物种可能通过替代策略适应，或者需要不同浓度的烟雾或不同的热量水平。本研究是为数不多的几个表明新热带草原物种对烟雾具有积极的萌发和幼苗生长反应的例子之一。
