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Another Look At The Root Of The Angiosperms Reveals A Familiar Tale, Bryan Drew, Brad Ruhfel, Stephen Smith, Michael Moore, Barbara Briggs, Matthew Gitzendanner, Pamela Soltis, Douglas Soltis Feb 2014

Another Look At The Root Of The Angiosperms Reveals A Familiar Tale, Bryan Drew, Brad Ruhfel, Stephen Smith, Michael Moore, Barbara Briggs, Matthew Gitzendanner, Pamela Soltis, Douglas Soltis

Brad R. Ruhfel

Since the advent of molecular phylogenetics more than 25 years ago, a major goal of plant systematists has been to discern the root of the angiosperms. Although most studies indicate that Amborella trichopoda is sister to all remaining extant flowering plants, support for this position has varied with respect to both the sequence data sets and analyses employed. Recently, Goremykin et al. (2013) questioned the “Amborella-sister hypothesis” using a “noise-reduction” approach and reported a topology with Amborella + Nymphaeales (water lilies) sister to all remaining angiosperms. Through a series of analyses of both plastid genomes and mitochondrial genes, we continue …


Digitization Of Herbarium Specimens, A Collaborative Process, Lawrence Schmidt Jan 2014

Digitization Of Herbarium Specimens, A Collaborative Process, Lawrence Schmidt

Larry O Schmidt

Digital collections in museums, libraries, and other agencies are expanding rapidly. Digitization of books, maps, photographs, and other objects for both preservation and dissemination are changing the way libraries work. Librarians who have, historically, worked with collections in print formats are anxious to move toward digital content as the wave of the future. Rather than stand on the sidelines and watch as the digital movement passes by, librarians need to be proactive and create digital content using both collections within the libraries’ walls and proactively seek opportunities to work collaboratively with stakeholders outside of the libraries’ hallowed halls. The creation …


Combined Morphological And Molecular Phylogeny Of The Clusioid Clade (Malpighiales) And The Placement Of The Ancient Rosid Macrofossil Paleoclusia, Brad Ruhfel, Peter Stevens, Charles Davis Dec 2012

Combined Morphological And Molecular Phylogeny Of The Clusioid Clade (Malpighiales) And The Placement Of The Ancient Rosid Macrofossil Paleoclusia, Brad Ruhfel, Peter Stevens, Charles Davis

Brad R. Ruhfel

Premise of research. The clusioid clade is a member of the large rosid order Malpighiales and contains∼1900 species in five families: Bonnetiaceae, Calophyllaceae, Clusiaceae sensu stricto (s.s.), Hypericaceae, and Podostemaceae. Despite recent efforts to clarify their phylogenetic relationships using molecular data, no such data are available for several critical taxa, including especially Hypericum ellipticifolium (previously recognized in Lianthus), Lebrunia, Neotatea, Thysanostemon, and the second-oldest rosid fossil (∼90 Ma), Paleoclusia chevalieri. Here, we (i) assess congruence between phylogenies inferred from morphological and molecular data, (ii) analyze morphological and molecular data simultaneously to place taxa lacking molecular data, and (iii) use ancestral …


Rocky Mountain Region Digital Herbarium, Larry Schmidt Dec 2012

Rocky Mountain Region Digital Herbarium, Larry Schmidt

Larry O Schmidt

No abstract provided.


Plant Classification And Nomenclature In Ndumba, Papua New Guinea Highlands, Terence Hays Nov 2012

Plant Classification And Nomenclature In Ndumba, Papua New Guinea Highlands, Terence Hays

Terence Hays

Traditionally, the terms "ethnobotany" and "ethnozoology" have designated little more than the study of plant and animal utilization. In the past two decades, however, the ways in which the components of given biological environments are locally perceived and categorized have received increasing attention. Not only has the study of ethnobiological classification been recognized as essential to a wide variety of ethnographic concerns (cf. Frake 1962; Bulmer 1967), but the discovery of possible universals in folk classification systems promises to enrich our understanding of human cognitive processes as well (Berlin et al. 1973; Brown 1977).

The paucity of comprehensive studies of …


Phylogenomics And A Posteriori Data Partitioning Resolve The Cretaceous Angiosperm Radiation Malpighiales, Zhenxiang Xi, Brad Ruhfel, Hanno Schaefer, André Amorim, M. Sugumaran, Kenneth Wurdack, Peter Endress, Merran Matthews, Peter Stevens, Sarah Mathews, Charles Davis Oct 2012

Phylogenomics And A Posteriori Data Partitioning Resolve The Cretaceous Angiosperm Radiation Malpighiales, Zhenxiang Xi, Brad Ruhfel, Hanno Schaefer, André Amorim, M. Sugumaran, Kenneth Wurdack, Peter Endress, Merran Matthews, Peter Stevens, Sarah Mathews, Charles Davis

Brad R. Ruhfel

The angiosperm order Malpighiales includes ∼16,000 species and constitutes up to 40% of the understory tree diversity in tropical rain forests. Despite remarkable progress in angiosperm systematics during the last 20 y, relationships within Malpighiales remain poorly resolved, possibly owing to its rapid rise during the mid-Cretaceous. Using phylogenomic approaches, including analyses of 82 plastid genes from 58 species, we identified 12 additional clades in Malpighiales and substantially increased resolution along the backbone. This greatly improved phylogeny revealed a dynamic history of shifts in net diversification rates across Malpighiales, with bursts of diversification noted in the Barbados cherries (Malpighiaceae), cocas …


Extreme Environments Select For Reproductive Assurance: Evidence From Evening Primroses (Oenothera), Margaret Evans, David Hearn, Kathryn Theiss, Karen Cranston, Kent Holsinger, Michael Donoghue Jun 2012

Extreme Environments Select For Reproductive Assurance: Evidence From Evening Primroses (Oenothera), Margaret Evans, David Hearn, Kathryn Theiss, Karen Cranston, Kent Holsinger, Michael Donoghue

Kent E Holsinger

• Competing evolutionary forces shape plant breeding systems (e.g. inbreeding depression, reproductive assurance). Which of these forces prevails in a given population or species is predicted to depend upon such factors as life history, eco- logical conditions, and geographical context. Here, we examined two such predictions: that self-compatibility should be associated with the annual life history or extreme climatic conditions.

• We analyzed data from a clade of plants remarkable for variation in breeding system, life history and climatic conditions (Oenothera, sections Anogra and Kleinia, Onagraceae). We used a phylogenetic comparative approach and Bayesian or hybrid Bayesian tests to account …


Forisome Performance In Artificial Sieve Tubes, Michael Knoblauch, Mike Stubenrauch, Aart J.E. Van Bel, Winfried S. Peters Mar 2012

Forisome Performance In Artificial Sieve Tubes, Michael Knoblauch, Mike Stubenrauch, Aart J.E. Van Bel, Winfried S. Peters

Winfried S. Peters

In the legume phloem, sieve element occlusion (SEO) proteins assemble into Ca2+-dependent contractile bodies. These forisomes presumably control phloem transport by forming reversible sieve tube plugs. This function, however, has never been directly demonstrated, and appears questionable as forisomes were reported to be too small to plug sieve tubes, and failed to block flow efficiently in artificial microchannels. Moreover, plugs of SEO-related proteins in Arabidopsis sieve tubes do not affect phloem translocation. We improved existing procedures for forisome isolation and storage, and found that the degree of Ca2+-driven deformation that is possible in forisomes of Vicia faba, the standard …


Effect Of Cercosporella Rubi On Blackberry Floral Bud Development, Kenneth Curry Mar 2012

Effect Of Cercosporella Rubi On Blackberry Floral Bud Development, Kenneth Curry

Kenneth J. Curry

Rosette, caused by the fungus Cercosporella rubi, is an important blackberry disease in the southeastern United States. This disease severely reduces fruit production, and its management has been erratic due to a limited understanding of the host-pathogen relationship. In this study, we expand on previous histological investigations of the development of C. rubi on blackberry at tissue and cellular levels from floral bud initiation through senescence of the flower. Symptomatic and asymptomatic floral buds were examined with light microscopy and both scanning and transmission electron microscopy (SEM and TEM, respectively). Fungal development on the surface of floral buds was …


Geometric Constraints And The Anatomical Interpretation Of Twisted Plant Organ Phenotypes, Renate Weizbauer, Winfried S. Peters, Burkhard Schulz Oct 2011

Geometric Constraints And The Anatomical Interpretation Of Twisted Plant Organ Phenotypes, Renate Weizbauer, Winfried S. Peters, Burkhard Schulz

Winfried S. Peters

The study of plant mutants with twisting growth in axial organs, which normally grow straight in the wild-type, is expected to improve our understanding of the interplay among microtubules, cellulose biosynthesis, cell wall structure, and organ biomechanics that control organ growth and morphogenesis. However, geometric constraints based on symplastic growth and the consequences of these geometric constraints concerning interpretations of twisted-organ phenotypes are currently underestimated. Symplastic growth, a fundamental concept in plant developmental biology, is characterized by coordinated growth of adjacent cells based on their connectivity through cell walls. This growth behavior implies that in twisting axial organs, all cell …


Plant-Animal Interactions, W. Abrahamson, T. Taylor Dec 2010

Plant-Animal Interactions, W. Abrahamson, T. Taylor

Warren G. Abrahamson, II

No abstract provided.


Münch, Morphology, Microfluidics – Our Structural Problem With The Phloem [Review Article], Michael Knoblauch, Winfried S. Peters Aug 2010

Münch, Morphology, Microfluidics – Our Structural Problem With The Phloem [Review Article], Michael Knoblauch, Winfried S. Peters

Winfried S. Peters

The sieve tubes of the phloem are enigmatic structures. Their role as channels for the distribution of assimilates was established in the 19th century, but their sensitivity to disturbations has hampered the elucidation of their transport mechanisms and its regulation ever since. Ernst Münch's classical monograph of 1930 is generally regarded as the first coherent theory of phloem transport, but the ‘Münchian’ pressure flow mechanism had been discussed already before the turn of the century. Münch's impact rather rested on his simple physical models of the phloem that visualized pressure flow in an intuitive way, and we argue that the …


Archaeobotany In Australia And New Guinea: Practice, Potential And Prospects, Tim Denham, Jennifer Atchison, Jeremy Austin, Sheahan Bestel, Doreen Bowdery, Alison Crowther, Nic Dolby, Andrew Fairbairn, Judith Field, Amanda Kennedy, Carol Lentfer, Carney Matheson, Sue Nugent, Jeffrey Parr, Matiu Prebble, Gail Robertson, Jim Specht, Robin Torrence, Huw Barton, Richard Fullagar, Simon Haberle, Mark Horrocks, Tara Lewis, Peter Matthews May 2010

Archaeobotany In Australia And New Guinea: Practice, Potential And Prospects, Tim Denham, Jennifer Atchison, Jeremy Austin, Sheahan Bestel, Doreen Bowdery, Alison Crowther, Nic Dolby, Andrew Fairbairn, Judith Field, Amanda Kennedy, Carol Lentfer, Carney Matheson, Sue Nugent, Jeffrey Parr, Matiu Prebble, Gail Robertson, Jim Specht, Robin Torrence, Huw Barton, Richard Fullagar, Simon Haberle, Mark Horrocks, Tara Lewis, Peter Matthews

Jeffrey Parr

Archaeobotany is the study of plant remains from archaeological contexts. Despite Australasian research being at the forefront of several methodological innovations over the last three decades, archaeobotany is now a relatively peripheral concern to most archaeological projects in Australia and New Guinea. In this paper, many practicing archaeobotanists working in these regions argue for a more central role for archaeobotany in standard archaeological practice. An overview of archaeobotanical techniques and applications is presented, the potential for archaeobotany to address key historical research questions is indicated, and initiatives designed to promote archaeobotany and improve current practices are outlined. ,


Legume Phylogeny And The Evolution Of A Unique Contractile Apparatus That Regulates Phloem Transport, Winfried Peters, Claudia Hanakam, Dietmar Haffer, Aart Van Bel, Michael Knoblauch Mar 2010

Legume Phylogeny And The Evolution Of A Unique Contractile Apparatus That Regulates Phloem Transport, Winfried Peters, Claudia Hanakam, Dietmar Haffer, Aart Van Bel, Michael Knoblauch

Winfried S. Peters

Protein bodies called forisomes undergo Ca2+-dependent deformations to occlude sieve tubes reversibly, providing a unique regulatory mechanism of phloem transport. Because forisomes are known exclusively from the Papilionoideae (Leguminosae), the evolution of forisome function may have played a role in the rapid radiation of this huge taxon. The unexpected discovery of a papilionoid species lacking forisomes led us to evaluate a representative set of species covering 33 of the 36 legume tribes traditionally recognized. We found forisomes in Papilionoideae but not in Caesalpinioideae and Mimosoideae. Forisomes were absent from several species of the papilionoid tribe Galegeae. Forisomes with tail-like protrusions …


My Embarrassment At Not Knowing Heinich, Winfried S. Peters Oct 2009

My Embarrassment At Not Knowing Heinich, Winfried S. Peters

Winfried S. Peters

This paper has no abstract; this is the first paragraph. The mechanisms of tissue tension phenomena and their physiological significance are controversial (Vincent and Jeronimidis, 1991; [Peters and Tomos, 1996a] and [Peters and Tomos, 1996b]; Kutschera and Niklas, 2007). Specifically, the apparently spontaneous expansion of inner tissues after removal of the peripheral cell layers is a perpetual bone of contention. We had reported evidence suggesting that inner tissue expansion is driven by water uptake (Peters and Tomos, 2000). Kutschera and Niklas (2007) rejected this interpretation and insisted that inner tissue expansion is an elastic response to the release from compressive …


Life History, Sexual Dimorphism And 'Ornamental' Feathers In The Mesozoic Bird Confuciusornis Sanctus., Winfried S. Peters, Dieter Stefan Peters Sep 2009

Life History, Sexual Dimorphism And 'Ornamental' Feathers In The Mesozoic Bird Confuciusornis Sanctus., Winfried S. Peters, Dieter Stefan Peters

Winfried S. Peters

The life history of Confuciusornis sanctus is controversial. Recently, the species’ body size spectrum was claimed to contradict osteohistological evidence for a rapid, bird-like development. Moreover, sexual size dimorphism was rejected as an explanation for the observed bimodal size distribution since the presence of elongated rectrices, an assumed ‘male’ trait, was uncorrelated with size. However, this interpretation (i) fails to explain the size spectrum of C. sanctus which is trimodal rather than bimodal, (ii) requires implausible neonate masses and (iii) is not supported by analogy with sexual dimorphisms in modern birds, in which elongated central rectrices are mostly sex-independent. Available …


Gfp Tagging Of Sieve Element Occlusion (Seo) Proteins Results In Green Fluorescent Forisomes, Hélène Pélissier, Winfried Peters, Ray Collier, Aart Van Bel, Michael Knoblauch Sep 2008

Gfp Tagging Of Sieve Element Occlusion (Seo) Proteins Results In Green Fluorescent Forisomes, Hélène Pélissier, Winfried Peters, Ray Collier, Aart Van Bel, Michael Knoblauch

Winfried S. Peters

Forisomes are Ca2+-driven, ATP-independent contractile protein bodies that reversibly occlude sieve elements in faboid legumes. They apparently consist of at least three proteins; potential candidates have been described previously as ‘FOR’ proteins. We isolated three genes from Medicago truncatula that correspond to the putative forisome proteins and expressed their green fluorescent protein (GFP) fusion products in Vicia faba and Glycine max using the composite plant methodology. In both species, expression of any of the constructs resulted in homogenously fluorescent forisomes that formed sieve tube plugs upon stimulation; no GFP fluorescence occurred elsewhere. Isolated fluorescent forisomes reacted to Ca2+ and chelators …


Anisotropic Contraction In Forisomes: Simple Models Won't Fit, Winfried Peters, Michael Knoblauch, Stephen Warmann, William Pickard, Amy Shen Mar 2008

Anisotropic Contraction In Forisomes: Simple Models Won't Fit, Winfried Peters, Michael Knoblauch, Stephen Warmann, William Pickard, Amy Shen

Winfried S. Peters

Forisomes are ATP-independent, Ca2+-driven contractile protein bodies acting as reversible valves in the phloem of plants of the legume family. Forisome contraction is anisotropic, as shrinkage in length is associated with radial expansion and vice versa. To test the hypothesis that changes in length and width are causally related, we monitored Ca2+- and pH-dependent deformations in the exceptionally large forisomes of Canavalia gladiata by high-speed photography, and computed time-courses of derived geometric parameters (including volume and surface area). Soybean forisomes, which in the resting state resemble those of Canavalia geometrically but have less than 2% of the volume, were also …


Tailed Forisomes Of Canavalia Gladiata: A New Model To Study Ca2+-Driven Protein Contractility, Winfried Peters, Michael Knoblauch, Stephen Warmann, Reinhard Schnetter, Amy Shen, William Pickard Jun 2007

Tailed Forisomes Of Canavalia Gladiata: A New Model To Study Ca2+-Driven Protein Contractility, Winfried Peters, Michael Knoblauch, Stephen Warmann, Reinhard Schnetter, Amy Shen, William Pickard

Winfried S. Peters

Background and Aims Forisomes are Ca2+-dependent contractile protein bodies that form reversible plugs in sieve tubes of faboid legumes. Previous work employed Vicia faba forisomes, a not entirely unproblematic experimental system. The aim of this study was to seek to establish a superior model to study these intriguing actuators.
Methods Existing isolation procedures were modified to study the exceptionally large, tailed forisomes of Canavalia gladiata by differential interference contrast microscopy in vitro. To analyse contraction/expansion kinetics quantitatively, a geometric model was devised which enabled the computation of time-courses of derived parameters such as forisome volume from simple parameters readily determined …


Reversible Birefringence Suggests A Role For Molecular Self-Assembly In Forisome Contractility, Winfried Peters, Reinhard Schnetter, Michael Knoblauch Apr 2007

Reversible Birefringence Suggests A Role For Molecular Self-Assembly In Forisome Contractility, Winfried Peters, Reinhard Schnetter, Michael Knoblauch

Winfried S. Peters

Forisomes are contractile protein bodies that control the effective diameter of the sieve elements of the faboid legumes by reversible, Ca2+-driven changes of shape. Forisomes consist of fibrils; we inferred from available electron-microscopical data (which necessarily provide images of fixed, non-functional forisomes) that a reversible assembly of ordered fibrillar arrays might be involved in the contractile mechanism. Here we examined functional forisomes isolated from Vicia faba L. by differential interference contrast microscopy and polarisation microscopy. We found them birefringent in the longitudinally expanded but not in the contracted state, showing ‘parallel extinction’ with the direction of vibration of the slow …


The Geometry Of The Forisome–Sieve Element–Sieve Plate Complex In The Phloem Of Vicia Faba L. Leaflets, Winfried Peters, Aart Van Bel, Michael Knoblauch Jul 2006

The Geometry Of The Forisome–Sieve Element–Sieve Plate Complex In The Phloem Of Vicia Faba L. Leaflets, Winfried Peters, Aart Van Bel, Michael Knoblauch

Winfried S. Peters

Forisomes are contractile protein bodies that appear to control flux rates in the phloem of faboid legumes by reversibly plugging the sieve tubes. Plugging is triggered by Ca2+ which induces an anisotropic deformation of forisomes, consisting of a longitudinal contraction and a radial expansion. By conventional light microscopy and confocal laser-scanning microscopy, the three-dimensional geometry of the forisome–sieve element–sieve plate complex in intact sieve tubes of leaflets of Vicia faba L. was reconstructed. Forisomes were mostly located close to sieve plates, and occasionally were observed drifting unrestrainedly along the sieve element, suggesting that they might be utilized as internal markers …


Forisome Based Biomimetic Smart Materials, Amy Shen, Benjamin Hamlington, Michael Knoblauch, Winfried Peters, William Pickard Jun 2006

Forisome Based Biomimetic Smart Materials, Amy Shen, Benjamin Hamlington, Michael Knoblauch, Winfried Peters, William Pickard

Winfried S. Peters

With the discovery in plants of the proteinaceous forisome crystalloid (Knoblauch, et al. 2003), a novel, non-living, ATP-independent biological material became available to the designer of smart materials for advanced actuating and sensing. The in vitro studies of Knoblauch, et al. show that forisomes (2-4 micron wide and 10-40 micron long) can be repeatedly stimulated to contract and expand anisotropically by shifting either the ambient pH or the ambient calcium ion concentration. Because of their unique abilities to develop and reverse strains greater than 20% in time periods less than one second, forisomes have the potential to outperform current smart …


Prospective Energy Densities In The Forisome, A New Smart Material, William Pickard, Michael Knoblauch, Winfried Peters, Amy Shen Dec 2005

Prospective Energy Densities In The Forisome, A New Smart Material, William Pickard, Michael Knoblauch, Winfried Peters, Amy Shen

Winfried S. Peters

The forisome is a protein structure of plants which, in low Ca2+ solutions, assumes a crystalline condensed conformation and, at high Ca2+, swells to a dispersed conformation; this transition has been attributed to electrostatic deformation of protein “modules”. Forisomes could become an important smart material if the energy density of transformation approached 1 MJ m−3. Quantitation of the forisome as a charged porous continuum permeated by electrolyte fails by orders of magnitude to achieve this energy density electrostatically. However, condensed → dispersed transitions can be visualized alternatively: (i) an ionic bond near the surface of a forisome crystal dissolves to …


Growth Rate Gradients And Extracellular Ph In Roots: How To Control An Explosion, Winfried S. Peters May 2004

Growth Rate Gradients And Extracellular Ph In Roots: How To Control An Explosion, Winfried S. Peters

Winfried S. Peters

This paper has no abstract; this is the first paragraph. As plant growth is restricted to defined zones of growing organs, the methodologically consistent analysis of spatial growth rate patterns in organ growth zones is prerequisite for studies into the regulation of cell growth in situ (Silk, 1984). The elongation zones at the tips of growing roots are classical objects of kinematic growth analysis, which aims at the quantitative description of growth rate gradients (Erickson & Sax, 1956). Root growth zones were generally believed to be characterized by growth rates that change gradually along bell-shaped growth gradients (Erickson & Sax, …


Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters Apr 2004

Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

This paper has no abstract; this is the first paragraph. Motility of cell components in both animal and plant cells is mostly based on the movement of motor proteins along actin filaments or microtubules [Boal, 2002]. The dominance of ATP hydrolysis as the energy source for such movements is so complete, that modern textbooks define “motor proteins” as nucleoside triphosphate-dependent actuators [e.g., Alberts et al., 2002]. In only one known case, a reversible mechanism of cell motility is driven by the interaction of Ca2+ and the responsive protein(s). Some sessile ciliates control the effective length of their stalk by means …


Atp-Independent Contractile Proteins From Plants, Michael Knoblauch, Gundula Noll, Torsten Müller, Dirk Prüfer, Ingrid Schneider-Hüther, Dörte Scharner, Aart Van Bel, Winfried Peters Aug 2003

Atp-Independent Contractile Proteins From Plants, Michael Knoblauch, Gundula Noll, Torsten Müller, Dirk Prüfer, Ingrid Schneider-Hüther, Dörte Scharner, Aart Van Bel, Winfried Peters

Winfried S. Peters

This paper has no abstract; this is the first paragraph. Emerging technologies are creating increasing interest in smart materials that may serve as actuators in micro- and nanodevices. Mechanically active polymers currently studied include a variety of materials. ATP-driven motor proteins, the actuators of living cells, possess promising characteristics, but their dependence on strictly defined chemical environments can be disadvantagous. Natural proteins that deform reversibly by entropic mechanisms might serve as models for artificial contractile polypeptides with useful functionality, but they are rare. Protein bodies from sieve elements of higher plants provide a novel example. sieve elements form microfluidics systems …


The Biophysics Of Leaf Growth In Salt-Stressed Barley. A Study At The Cell Level., Wieland Fricke, Winfried Peters Apr 2002

The Biophysics Of Leaf Growth In Salt-Stressed Barley. A Study At The Cell Level., Wieland Fricke, Winfried Peters

Winfried S. Peters

Biophysical parameters potentially involved in growth regulation were studied at the single-cell level in the third leaf of barley (Hordeum vulgare) after exposure to various degrees of NaCl stress for 3 to 5 d. Gradients of elongation growth were measured, and turgor pressure, osmolality, and water potentials (ψ) were determined (pressure probe and picoliter osmometry) in epidermal cells of the elongation zone and the mature blade. Cells in the elongation zone adjusted to decreasing external ψ through increases in cell osmolality that were accomplished by increased solute loads and reduced water contents. Cell turgor changed only slightly. In …


Reversible Calcium-Regulated Stopcocks In Legume Sieve Tubes, Michael Knoblauch, Winfried Peters, Katrin Ehlers, Aart Van Bel Apr 2001

Reversible Calcium-Regulated Stopcocks In Legume Sieve Tubes, Michael Knoblauch, Winfried Peters, Katrin Ehlers, Aart Van Bel

Winfried S. Peters

Sieve tubes of legumes (Fabaceae) contain characteristic P-protein crystalloids with controversial function. We studied their behavior by conventional light, electron, and confocal laser scanning microscopy. In situ, crystalloids are able to undergo rapid (<1>sec) and reversible conversions from the condensed resting state into a dispersed state, in which they occlude the sieve tubes. Crystalloid dispersal is triggered by plasma membrane leakage induced by mechanical injury or permeabilizing substances. Similarly, abrupt turgor changes imposed by osmotic shock cause crystalloid dispersal. Because chelators generally prevent the response, divalent cations appear to be the decisive factor in crystalloid expansion. Cycling between dispersal and …


Does Growth Correlate With Turgor-Induced Elastic Strain In Stems? A Re-Evaluation Of De Vries' Classical Experiments, Winfried Peters, Maggie Farm, A. Kopf Mar 2001

Does Growth Correlate With Turgor-Induced Elastic Strain In Stems? A Re-Evaluation Of De Vries' Classical Experiments, Winfried Peters, Maggie Farm, A. Kopf

Winfried S. Peters

The correlation between growth and turgor-induced elastic expansion was studied in hypocotyls of sunflower (Helianthus annuus) seedlings under various growth conditions. Turgor-induced elastic cell wall strain was greater in hypocotyls of faster growing seedlings, i.e. in etiolated versus light-grown ones. It also was higher in rapidly growing young seedlings as compared with nongrowing mature ones. However, analysis of the spatial distribution of elastic strain and growth demonstrated that their correspondence was only apparent. Profiles of elastic strain declined steadily from the top of the hypocotyls toward the basis, whereas the profiles of relative elemental growth rate along the …


The Mechanic State Of “Inner Tissue” In The Growing Zone Of Sunflower Hypocotyls And The Regulation Of Its Growth Rate Following Excision, Winfried Peters, A. Tomos May 2000

The Mechanic State Of “Inner Tissue” In The Growing Zone Of Sunflower Hypocotyls And The Regulation Of Its Growth Rate Following Excision, Winfried Peters, A. Tomos

Winfried S. Peters

Spontaneous growth of isolated inner tissue from the etiolated sunflower (Helianthus annuus L.) hypocotyl growing zone was investigated. A new preparation technique allowed measurements starting 3 s after excision. Elongation with respect to the turgescent and plasmolized state was quantified in terms of relative growth rates, facilitating comparison to growth in situ. Turgor and turgor-induced strain were determined. Overall longitudinal strain in inner tissues in situ was positive, indicating that compressive forces exerted by peripheral tissues are outweighed by turgor-dependent tensile stress. Inner tissue expansion following isolation depended on water uptake. Extreme plastic extension rates occurred immediately after excision, …