The Mechanics of Seed Expulsion in Acanthaceae

Witztum, A.; Schulgasser, K.

doi:10.1006/jtbi.1995.0219

Cited by 75 publications

(52 citation statements)

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“…Os frutos são secos, do tipo cápsulas loculicidas, que amadurecem em ca. de 30-40 dias e abrem explosivamente (ver Witztum & Schulgasser 1995 Tabela 2. Visitantes das flores de Ruellia brevifolia, sua freqüência de visitas, categoria dos visitantes e recursos florais utilizados.…”

Section: Resultsunclassified

Ruellia brevifolia (Pohl) Ezcurra (Acanthaceae): fenologia da floração, biologia da polinização e reprodução

Sigrist¹,

Sazima²

2002

Rev. bras. Bot.

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-(Ruellia brevifolia (Pohl) Ezcurra (Acanthaceae): flowering phenology, pollination biology and reproduction). The reproductive biology of Ruellia brevifolia was studied in two populations of southeastern Brazil. R. brevifolia is a shrublet that grows in dense clumps in open but shaded areas. This Acanthaceae blooms all year round and produces chasmogamous (CH) and cleistogamous (CL) flowers during the rainy and the dry season, respectively. Cleistogamy is of the "clymatic" type, and produces seeds in the most stressful period of the year. CH flowers are tubular, red and odourless, protogynous, and may be herkogamous or not; anthesis is diurnal, and they last two days. Nectar is produced in small amounts (5.2 µl ± 2.36) and its concentration is about 30%. CL flowers resemble CH buds, except for their pale color. Pollen/ovule ratio of CL flowers is 60% lesser than that of CH flowers because of the small amount of pollen grains. This Ruellia is self-compatible, but protogyny and herkogamy favour allogamy; spontaneous self-pollination in CH flowers seems to be related to the non herkogamous flowers. The hummingbird Amazilia lactea and the butterflies Heliconius etilla narcaea and Phoebis argante are the major pollinators of R. brevifolia. The hummingbirds visit R. brevifolia only during flowering peaks, when there is a high number of flowers. It seems plausible that both the small nectar volume per flower and the trap-line foraging strategy of A. lactea promote mainly outcrossing. The butterflies visit flowers mainly in the same plant group, but during low floral density periods they fly greater distances also favouring outcrossing.RESUMO -(Ruellia brevifolia (Pohl) Ezcurra (Acanthaceae): fenologia da floração, biologia da polinização e reprodução). A biologia reprodutiva de Ruellia brevifolia foi estudada em populações naturais do sudeste brasileiro. R. brevifolia é um subarbusto que forma agrupamentos densos em áreas abertas mas sombreadas e floresce o ano todo, produzindo flores casmógamas (CH) e cleistógamas (CL) nas estações úmida e seca, respectivamente. A cleistogamia é do tipo climática, originando sementes no período de maior estresse ambiental. Flores CH são inodoras e possuem corola tubulosa e vermelha, sendo hercogâmicas ou não; apresentam protoginia, antese diurna e duram dois dias. Néctar é o principal recurso floral, sendo produzido em baixa quantidade (5,2 µl ± 2,36) e com concentração de açúcares em torno de 30%. Flores CL assemelham-se a botões jovens de flores CH e apresentam redução de tamanho principalmente no androceu e na corola. A razão pólen/óvulo das flores CL é ca. de 60% menor que a das flores CH devido a menor quantidade de grãos de pólen. R. brevifolia é autocompatível embora alogamia seja favorecida pela protoginia e pelas flores hercogâmicas. Autopolinização espontânea parece estar relacionada às flores CH não hercogâmicas. Beija-flores, principalmente Amazilia lactea, e borboletas, em especial Heliconius etilla narcaea e Phoebis argante, são os polinizadores de R. brevifoli...

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Section: Resultsunclassified

Ruellia brevifolia (Pohl) Ezcurra (Acanthaceae): fenologia da floração, biologia da polinização e reprodução

Sigrist¹,

Sazima²

2002

Rev. bras. Bot.

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“…The actuating tissue is often built of two parts: an active part that is able to contract and a resistance part that stabilizes the stress or torsion developed during drying. In some devices designed for explosive seed expulsion, where the movement of the active part is restricted, there is an intermediate tissue that maximizes the energy stored in the device (Witztum and Schulgasser, 1995).…”

Section: Introductionmentioning

confidence: 99%

Structures in the cell wall that enable hygroscopic movement of wheat awns

Elbaum

Gorb²,

Fratzl

2008

Journal of Structural Biology

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“…The mechanism of hygroscopic movement is a consequence of wetting and drying of tissue, which results in different anisotropic swelling in different regions of the tissue. Humidity-driven movement is not only shown in wheat awns, it is also reported for various other species [5][6][7][8][9]. This movement is interesting for the (bio)materials engineer as the movement occurs without an active metabolism and as such is controlled solely by the architectural arrangement of the different swellable tissues.…”

Section: Introductionmentioning

confidence: 53%

Finite Element Modeling of the Cyclic Wetting Mechanism in the Active Part of Wheat Awns

et al. 2012

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Many plant tissues and organs are capable of moving due to changes in the humidity of the environment, such as the opening of the seed capsule of the ice plant and the opening of the pine cone. These are fascinating examples for the materials engineer, as these tissues are non-living and move solely through the differential swelling of anisotropic tissues and in principle may serve as examples for the bio-inspired design of artificial actuators. In this paper, we model the microstructure of the wild wheat awn (Triticum turgidum ssp. dicoccoides) by finite elements, especially focusing on the specific microscopic features of the active part of the awn. Based on earlier experimental findings, cell walls are modeled as multilayered cylindrical tubes with alternating cellulose fiber orientation in successive layers. It is shown that swelling upon hydration of this system leads to the formation of gaps between the layers, which could act as valves, thus enabling the entry of water into the cell wall. This supports the hypothesis that this plywood-like arrangement of cellulose fibrils enhances the effect of ambient humidity by accelerated water or vapor diffusion along the gaps. The finite element model shows that a certain distribution of axially and tangentially oriented fibers is necessary to generate sufficient tensile stresses within the cell wall to open nanometer-sized gaps between cell wall layers.

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The Mechanics of Seed Expulsion in Acanthaceae

Cited by 75 publications

References 0 publications

Ruellia brevifolia (Pohl) Ezcurra (Acanthaceae): fenologia da floração, biologia da polinização e reprodução

Ruellia brevifolia (Pohl) Ezcurra (Acanthaceae): fenologia da floração, biologia da polinização e reprodução

Structures in the cell wall that enable hygroscopic movement of wheat awns

Finite Element Modeling of the Cyclic Wetting Mechanism in the Active Part of Wheat Awns

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