Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora

Moreira, Bruno; Tormo, Jaume; Estrelles, Elena; Pausas, Juli G.

doi:10.1093/aob/mcq017

Cited by 194 publications

(216 citation statements)

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“…Keeley et al 2011). Several species from Mediterranean ecosystems show fire-related cues to germi- nation (see Moreira et al 2010), being fire-dependent, while other species can germinate after temperature fluctuations (gap-dependent, Ooi et al 2014). Our study showed that only seeds of Stylosanthes montevidensis had a fire-related increase in germination after the exposure to 120ºC, showing breakage of physical dormancy of at least 20% of the seeds.…”

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confidence: 54%

“…Fire-related germination is found in different types of vegetation, but most studies describe this relationship in Mediterranean ecosystems (see Reyes & Trabaud 2009;Moreira et al 2010) and in Australia (see Auld & O'Connell 1991;Ooi et al 2014). Keeley et al (2011) concluded thus, that breaking the dormancy or stimulating the germination by fire cues should be considered as evidence for selective pressures in plant evolution.…”

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confidence: 99%

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To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

2016

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Fire plays an important role in several grassland ecosystems in the world. Fire can trigger germination in several species, by breaking the physical dormancy of their seeds. Thus, we hypothesized that exposure to high temperatures during fire would break seed dormancy and enhance germination. We tested the effect of high temperatures on the germination of six species of legumes from Brazilian subtropical grasslands. We used heat shock experiments with the following treatments: 60, 90, 120 and 150ºC for one minute. Seeds were then placed to germinate for 60 days in 12/12 hours light/dark and 20/30ºC. Germination was generally low for all study species. Most species was not affected by heat shock treatments. However, Stylosanthes montevidensis was the only species that had its physical dormancy broken when exposed to 120ºC. The seeds of all the other species were neither stimulated nor killed by high temperatures. Although the exposure to high temperatures did not affect the germination of the study species (except for one), it also did not kill seeds, thereby showing that seeds are resistant to fire. Therefore, the rapid passage of fire in these grasslands is not sufficient to break the dormancy of most of the studied species of legumes.

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To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

2016

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“…Temperatures reached during the passage of fire can break physical dormancy of hard-coated seeds, allowing subsequent water imbibition and germination when environmental conditions are suitable (Auld and O'Connell 1991;Keeley 1991;Cocks and Stock 1997;Bell 1999). In addition, smoke can also affect the physiology of seeds and directly stimulate germination (Brown 1993;Dixon et al 1995;Keeley and Fotheringham 1998;Van Staden et al 2000;Moreira et al 2010) or act in combination with heat (Keeley 1991;Keith 1997;Morris 2000;Thomas et al 2003). Other direct fire cues, such as charred wood, can also act to stimulate seed germination in some species (Keeley 1987).…”

Section: Introductionmentioning

confidence: 99%

Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species

et al. 2010

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M. (2010). Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species. Australian Journal of Botany, 58 (7), 539-545.Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species AbstractIn addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0-2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues. © 2010 CSIRO. Abstract. In addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0-2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues.

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“…Heat shock and chemicals derived from smoke, ashes or charred wood are the cues often proposed by ecologists to test and illus-trate fire-stimulated germination (e.g. Keeley, 1987;Moreira et al, 2010;Thomas et al, 2010). Fire-cued germination has been considered to be adaptive in fire-prone environments, since it makes seedling emergence coincide with temporary favourable conditions, where light and soil nutrients increase and negative biotic interactions (e.g.…”

Section: Introductionmentioning

confidence: 99%

Heat shock and plant leachates regulate seed germination of the endangered carnivorous plant <i>Drosophyllum lusitanicum</i>

et al. 2018

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Abstract. In fire-prone ecosystems, many plant species have specialized mechanisms of seed dormancy that ensure a successful recruitment after fire. A well-documented mechanism is the germination stimulated by firerelated cues, such as heat shock and smoke. However, less is known about the role of inhibitory germination signals (e.g. allelopathy) in regulating post-fire recruitment. Plant leachates derived from the unburned vegetation can enforce dormancy by means of allelopathic compounds, acting as a signal of unfavourable (highly competitive) niche for germination in pyrophyte species. Here, we assessed the separate effects of heat shock and plant leachates on seed germination of Drosophyllum lusitanicum, an endangered carnivorous plant endemic to Mediterranean fire-prone heathlands. We performed a germination experiment in which seeds were subjected to three treatments: (1) 5 min at 100 • C, (2) watering with plant leachate, and (3) control. Germination rate and seed viability was determined after 63 days. Heat shock stimulated seed germination in D. lusitanicum while plant leachates had inhibitory germination effects without reducing seed viability. Thus, both positive and negative signals could be involved in its successful post-fire recruitment. Fire would break seed dormancy and stimulate seed germination of D. lusitanicum through high temperatures, but also by eliminating allelochemical compounds from the soil. These results help to understand the population dynamics patterns found for D. lusitanicum in natural populations, and highlight the role of fire in the ecology and conservation of this endangered species. Seed dormancy imposed by plant-derived leachates as an adaptive mechanism should be considered more in fire ecology theory.

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Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora

Abstract: The results suggest that both heat and smoke are important germination cues in a wide range of MB woody species and that fire-cued germination in woody plants of the MB may be as important as in other MTEs.

Cited by 194 publications

References 44 publications

To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species

Heat shock and plant leachates regulate seed germination of the endangered carnivorous plant <i>Drosophyllum lusitanicum</i>

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Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora

Abstract: The results suggest that both heat and smoke are important germination cues in a wide range of MB woody species and that fire-cued germination in woody plants of the MB may be as important as in other MTEs.

Cited by 194 publications

References 44 publications

To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species

Heat shock and plant leachates regulate seed germination of the endangered carnivorous plant &lt;i&gt;Drosophyllum lusitanicum&lt;/i&gt;

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Heat shock and plant leachates regulate seed germination of the endangered carnivorous plant <i>Drosophyllum lusitanicum</i>