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Wind-dispersed plants have evolved ingenious ways to lift their seeds1,2. The common dandelion uses a bundle of drag-enhancing bristles (the pappus) that helps to keep their seeds aloft. This passive flight mechanism is highly effective, enabling seed dispersal over formidable distances3,4; however, the physics underpinning pappus-mediated flight remains unresolved. Here we visualized the flow around dandelion seeds, uncovering an extraordinary type of vortex. This vortex is a ring of recirculating fluid, which is detached owing to the flow passing through the pappus. We hypothesized that the circular disk-like geometry and the porosity of the pappus are the key design features that enable the formation of the separated vortex ring. The porosity gradient was surveyed using microfabricated disks, and a disk with a similar porosity was found to be able to recapitulate the flow behaviour of the pappus. The porosity of the dandelion pappus appears to be tuned precisely to stabilize the vortex, while maximizing aerodynamic loading and minimizing material requirements. The discovery of the separated vortex ring provides evidence of the existence of a new class of fluid behaviour around fluid-immersed bodies that may underlie locomotion, weight reduction and particle retention in biological and manmade structures.
Assuntos
Dispersão de Sementes , Sementes/anatomia & histologia , Sementes/fisiologia , Taraxacum/anatomia & histologia , Taraxacum/fisiologia , Vento , Movimento (Física) , PorosidadeRESUMO
Savage et al. and Mehr et al. provide well-substantiated arguments that the evolution of musicality was shaped by adaptive functions of social bonding and credible signalling. However, they are too quick to dismiss byproduct explanations of music evolution, and to present their theories as complete unitary accounts of the phenomenon.
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Música , Evolução Biológica , HumanosRESUMO
The degree of shoot branching in Arabidopsis is determined by the activation of axillary buds. Bud activity is regulated by diverse environmental and developmental signals, often mediated via plant hormones, including auxin, strigolactone and cytokinin. The transcription factor BRANCHED1 (BRC1) has been proposed to integrate these regulatory signals. This idea is based on increased branching in brc1 mutants, the effects of bud-regulating hormones on BRC1 expression, and a general correlation between BRC1 expression and bud growth inhibition. These data demonstrate the important role of BRC1 in shoot branching, but here we show that in Arabidopsis this correlation can be broken. Buds lacking BRC1 expression can remain inhibited and sensitive to inhibition by strigolactone. Furthermore, buds with high BRC1 transcript levels can be active. Based on these data, we propose that BRC1 regulates bud activation potential in concert with an auxin transport-based mechanism underpinning bud activity. In the context of strigolactone-mediated bud regulation, our data suggest a coherent feed-forward loop in which strigolactone treatment reduces the probability of bud activation by parallel effects on BRC1 transcription and the shoot auxin transport network.
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Proteínas de Arabidopsis/genética , Arabidopsis/embriologia , Arabidopsis/genética , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Brotos de Planta/embriologia , Brotos de Planta/genética , Fatores de Transcrição/genética , Arabidopsis/efeitos dos fármacos , Proteínas de Arabidopsis/metabolismo , Epistasia Genética/efeitos dos fármacos , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Ácidos Indolacéticos/farmacologia , Lactonas/farmacologia , Mutação/genética , Brotos de Planta/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Fatores de Transcrição/metabolismoRESUMO
Plant dispersal mechanisms rely on anatomical and morphological adaptations for the use of physical or biological dispersal vectors. Recently, studies of interactions between the dispersal unit and physical environment have uncovered fluid dynamic mechanisms of seed flight, protective measures against fire, and release mechanisms of explosive dispersers. Although environmental conditions generally dictate dispersal distances, plants are not purely passive players in these processes. Evidence suggests that some plants may enact informed dispersal, where dispersal-related traits are modified according to the environment. This can occur via developmental regulation, but also on shorter timescales via structural remodelling in relation to water availability and temperature. Linking interactions between dispersal mechanisms and environmental conditions will be essential to fully understand population dynamics and distributions.
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Dispersão de Sementes/fisiologia , Animais , Fenômenos Biomecânicos , Meio Ambiente , Modelos Biológicos , Desenvolvimento VegetalAssuntos
Ácido Abscísico/metabolismo , Etilenos/metabolismo , Proteínas F-Box/metabolismo , Frutas/crescimento & desenvolvimento , Frutas/metabolismo , Musa/crescimento & desenvolvimento , Musa/metabolismo , Transdução de Sinais/efeitos dos fármacos , Produtos Agrícolas/crescimento & desenvolvimento , Produtos Agrícolas/metabolismo , Regulação da Expressão Gênica de PlantasRESUMO
Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.
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Highlights from the Science family of journals.