Detecting karrikinolide responses in seeds of the Poaceae

The Cerrado (Brazilian savanna) is a biodiversity hotspot with a history of fire that goes back as far as 10 million years. Fire has influenced the evolution of several aspects of the vegetation, including reproduction and life cycles. This study tested how fire by‐products such as heat and smoke affect the germination of six species common to two Cerrado open physiognomies: wet grasslands and the campo sujo (grassland with scattered shrubs and dwarf trees). We subjected seeds collected in northern Brazil to heat shock and smoke treatments, both separately and combined, using different temperatures, exposure times, and smoke concentrations in aqueous solutions. High temperatures and smoke did not break seed dormancy nor stimulate germination of the Cerrado study species. However, seeds were not killed by high temperatures, indicating that they are fire‐tolerant. Our findings differed from those of other fire‐prone ecosystems (mostly of Mediterranean vegetation), where fire stimulates germination. Moreover, we provide important information regarding germination strategies of non‐woody Cerrado plants, showing the importance of considering the tolerance of seeds to high temperatures when evaluating fire‐related traits in fire‐prone ecosystems.

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“…However, responses to smoke solutions are complex and may also depend on other factors, such as temperature and light (Long et al . ).…”

Section: Discussionmentioning

confidence: 97%

Does Fire Trigger Seed Germination in the Neotropical Savannas? Experimental Tests with Six Cerrado Species

et al. 2016

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“…The preincubation experiments also indicated higher sensitivity of caryopses to KAR 1 than to GA 3 . Previously, it was also demonstrated that KAR 1 (Daws et al 2007;Kępczyński et al 2010;Kępczyński and Van Staden 2012;Long et al 2011;Stevens et al 2007) and GA 3 (Adkins et al 1986; Daws et al 2007; Kępczyński et al 2006;Stevens et al 2007) stimulated germination of dormant and partially dormant A. fatua caryopses. Dry storage (after-ripening), is commonly used to remove seed dormancy in many plant species, including A. fatua caryopses.…”

Section: Discussionmentioning

confidence: 99%

Necessity of gibberellin for stimulatory effect of KAR1 on germination of dormant Avena fatua L. caryopses

2012

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Avena fatua L. florets (caryopses enclosed by lemma and palea) were partially dormant at 10-20°C and did not germinate at temperatures outside this range. Afterripening florets at 25°C for 12 weeks completely removed dormancy. Caryopses (florets without lemma and palea) were able to germinate totally at 20°C. Karrikinolide (KAR 1 ) and gibberellic acid (GA 3 ) applied at 10-25°C partially or markedly induced germination of dormant florets and caryopses, respectively. Both florets and caryopses were more sensitive to KAR 1 than to GA 3 . To obtain similar effects, 1,000 to 10,000 times lower concentrations of KAR 1 than GA 3 were required. After-ripening with time gradually increased sensitivity of caryopses to these regulators. Likewise, after-ripened, non-dormant caryopses were sensitive to KAR 1 and GA 3 . Inhibitors of gibberellin biosynthesis, ancymidol, paclobutrazol and flurprimidol inhibited the effect of KAR 1 . This inhibition was reversed by GA 3 . Caryopses pre-incubated in water with ancymidol or paclobutrazol in the presence or absence of KAR 1 germinated completely but with different rates after transfer to GA 3 . KAR 1 probably requires gibberellin biosynthesis to stimulate germination of dormant Avena fatua L. caryopses. Both KAR 1 and GA 3 increased a-amylase, b-amylase and dehydrogenases activities during imbibition before visible germination occurred.

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“…moisture, temperature, light) and chemical (see examples below) environment. The roles of moisture and temperature in alleviating physiological dormancy are particularly well studied, and the following naturally occurring processes may contribute to dormancy loss: ( i ) dry after‐ripening (sustained dry conditions) (Foley, ; Chauhan & Johnson, ; Iglesias‐Fernández, del Carmen Rodríguez‐Gacio & Matilla, ); ( ii ) cold and warm stratification (wet conditions below or above 10°C, respectively) (Schütz & Rave, ; Turner et al , ; Footitt et al , , ); ( iii ) wet‐dry cycling (alternating periods of wetting and drying) (Gallagher, Steadman & Crawford, ; Batlla & Benech‐Arnold, ; Hoyle et al , 2008 a ; Long et al , 2011 b ); and ( iv ) alternating temperatures (Batlla & Benech‐Arnold, ; Footitt et al , ; Long et al , 2011 c ).…”

Section: Seed Characteristics That Influence Persistencementioning

confidence: 99%

The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demise

et al. 2014

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Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long-term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed-bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance-exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments.

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Detecting karrikinolide responses in seeds of the Poaceae

Cited by 37 publications

References 32 publications

Does Fire Trigger Seed Germination in the Neotropical Savannas? Experimental Tests with Six Cerrado Species

Does Fire Trigger Seed Germination in the Neotropical Savannas? Experimental Tests with Six Cerrado Species

Necessity of gibberellin for stimulatory effect of KAR1 on germination of dormant Avena fatua L. caryopses

The ecophysiology of seed persistence: a mechanistic view of the journey to germination or demise

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