Showing papers in "Botany in 2005"
TL;DR: A dichotomous key and annotated descriptions for a cross-section of the most common dark septate endophytes are provided, sometimes used to imply taxonomic and physiological similarity even though a diverse range of root endophytic taxa form pigmented hyphae.
Abstract: A wide range of ascomycetous microfungi inhabits roots without forming the anatomical features typical of mycorrhizas or causing overt signs of pathogenesis. The most-studied taxa have darkly pigme...
217 citations
TL;DR: A small number of leaves per species was sufficient for establishing a characteristic pattern for each of them, which constitutes an important advantage of the method in the recognition and classification procedure.
Abstract: A new method is proposed for the extraction of morphometric characteristics of plant leaf structures. A sample of 10 species of the genus Passiflora (P. coriacea Juss., P. foetida L., P. miersii Ma...
164 citations
TL;DR: Algae that appear to lack a carbon-concentrating mechanism (CCM) are considered, certain environmental, biochemi- cal, and biophysical factors may permit the occurrence of algae lacking CCMs.
Abstract: Most of the algae and cyanobacteria that have been critically examined express a carbon-concentrating mechanism (CCM) when grown at, or below, the current atmospheric CO2 concentration. This paper considers algae that appear to lack a CCM. Critical examination of the evidence on which the presence or absence of a CCM is de- cided shows that more information is frequently needed before the criteria can be fully applied. Examples are the path- ways of glycolate metabolism in nongreen algae, and the 13 C/ 12 C discrimination shown by form ID Rubisco in vitro. The available evidence suggests that the algae lacking CCMs are some terrestrial green microalgae, some florideophyte freshwater red macroalgae, and a number of florideophyte red macroalgae from the supralittoral, littoral, and sublittoral, and almost all of the freshwater chrysophytes and synurophytes examined. Certain environmental, biochemi- cal, and biophysical factors may permit the occurrence of algae lacking CCMs. The absence of CCMs is presumably the plesiomorphic (i.e., ancestral) condition in cyanobacteria (and algae?). Resume : La plupart des algues et des cyanobacteries, qui ont ete examinees attentivement, possedent un mecanisme de concentration du carbone (CCM), lorsqu'elles sont cultivees a des concentrations de CO2 egales ou inferieures a celle de l'atmosphere. Les auteurs examinent ici les algues qui n'ont pas de CCM. Un examen critique des preuves sur lesquelles la presence ou l'absence d'un CCM est reconnue, montre qu'il faut souvent plus d'informations avant que le critere puisse etre applique. Par exemple, on note les sentiers metaboliques du glycolate chez les algues nonvertes, et la discrimination des 13 C/ 12 C manifestee par la forme ID de la Rubisco. Les preuves actuelles suggerent que les algues qui n'ont pas de CCM sont certaines microalgues vertes terrestres, certaines macro-algues rouges florideophytes d'eau douce, et un nombre de macroalgues rouges florideophytes du supralittoral, du littoral et du sublittoral, ainsi que la plupart des chrysophytes et des synurophytes d'eau douce examinees. Certains facteurs environnementaux, biochimiques et biophysiques peuvent permettre la presence d'algues depourvues de CCM. L'absence de CCM constitue vraisembla- blement la condition plesiomorphe (c.-a-d. ancestrale), chez les cyanobacteries. Mots cles : diffusion du CO2, algues chrysophytes, ecologie, evolution, algues vertes, photosynthese, algues rouges. (Traduit par la Redaction) Raven et al. 890
150 citations
TL;DR: Results from maximum parsimony analyses of the cpDNA and ITS and ITS/trnL sequence data showed a monophyletic origin for the tribe Brassiceae, with the inclusion of controversial members Calepina, Conringia, and Orychophragmus.
Abstract: Using sequence data from the ITS region (internal transcribed spacers ITS-1 and ITS-2 of nuclear DNA and the 5.8 rRNA gene), chloroplast DNA (cpDNA) sequence data from the trnL intron, and cpDNA re...
133 citations
TL;DR: It is shown that plant genotype can impact hidden ecological players (i.e., fungal endophytes) resulting in community and ecosystem consequences.
Abstract: Recent studies have shown effects of host plant genetics on community and ecosystem processes, which makes understanding the impacts of genetically based traits on hidden or non-apparent organisms ...
121 citations
TL;DR: It is suggested that, over short time frames, 1-ha-sized aggregates are sufficient to maintain most common mosses through structural retention harvests but are not large enough to prevent declines or losses of liverworts.
Abstract: Limited information exists on the effects of forest management practices on bryophytes, despite their impor- tance to forest ecosystems. We examined short-term responses of ground-layer bryophytes to logging disturbance and creation of edges in mature Pseudotsuga forests of western Washington (USA). The abundance and richness of species were measured in four 1-ha forest aggregates (patches of intact forest) and in surrounding logged areas before and after structural retention harvests. One year after treatment, species richness, total cover, and frequency of most moss and liverwort taxa declined within harvest areas. Within forest aggregates, mosses did not show significant edge effects; however, richness and abundance of liverworts declined with proximity to the aggregate edge. Our results suggest that, over short time frames, 1-ha-sized aggregates are sufficient to maintain most common mosses through structural reten- tion harvests but are not large enough to prevent declines or losses of liverworts. Thus, current standards for structural retention, which allow for aggregates as small as 0.2 ha, may be inadequate to retain the diversity and abundance of species found in mature, undisturbed forests.
110 citations
TL;DR: The hypothesis that the CO2/O2 ratio plays any role in signaling for the up-regulation of limiting CO2-induced genes and (or) of theCO2-concentrating mechanism (CCM) is failed.
Abstract: Growth, photosynthesis, and induction of two low CO2-inducible genes of Chlamydomonas reinhardtii Dangeard strain CC125 were quantified in a range of physiologically relevant CO2 and O2 concentrations (5%0.005% CO2 and 20% or 2% O2) using airlift bioreactors to facilitate the simultaneous measurement of both growth and in situ photosynthetic rates. Within these CO2 concentration ranges, O2 concentrations (20% vs. 2%) had no discernable effect on growth, photosynthetic rate, or induction of the periplasmic carbonic anhydrase (Cah1) and glycolate dehydrogenase (Gdh) genes in wild-type C. reinhardtii. These results failed to support the hypothesis that the CO2/O2 ratio plays any role in signaling for the up-regulation of limiting CO2-induced genes and (or) of the CO2-concentrating mechanism (CCM). The mRNA abundance of the Cah1 and Gdh genes appeared to be regulated in concert, suggesting co-regulation by the same signaling pathway, which, because of a lack of an O2 effect, seems unlikely to involve photore...
103 citations
TL;DR: It is revealed that abandoned mined peatlands have a high diversity of peatland vascular plants species and a low di- versity of non-peatland species.
Abstract: Many North American peatlands previously mined for horticultural peat have been abandoned recently, al- lowing natural recolonization to occur. The two dominant methods for peat extraction, hand block-cutting and vacuum- mining, have created distinctly different abandoned surfaces, leading to different recolonization patterns. Both types of exploitation can be found throughout eastern Canada where we conducted a vast survey of 26 abandoned mined peatlands in the provinces of Quebec and New Brunswick. The aim of this study is to describe the revegetation pat- terns and to assess the impact of local and regional variables as well as the time since abandonment on Sphagnum re- colonization. We inventoried the vegetation structure in all trenches (2571) and baulks (2595) of abandoned block-cut areas as well as in all vacuum fields (395) of the mechanically mined areas. We also conducted detailed species releves in 242 of these peat fields. In comparison to vacuum-mined peatlands, block-cut peatlands regenerated remarkably well. Approximately 80% of all baulks and trenches in block-cut peatlands had 50% or higher cover of ericaceous shrubs compared with only 16% found on vacuum fields. Herb cover in the three types of abandoned fields was similar to that in natural peatlands. However, Sphagnum percent cover was below 2% in baulks and vacuum fields and was 30% on average in the trenches, which is clearly below cover estimates in natural peatlands. Sphagnum cover and richness were both higher in trenches with thin residual peat deposit, and Sphagnum richness increased with latitude. Our sur- veys revealed that abandoned mined peatlands have a high diversity of peatland vascular plants species and a low di- versity of non-peatland species.
103 citations
TL;DR: Whether diatoms possess the enzymic and structural components necessary for a C4-type CO2-concentrating mechanism is discussed and these are compared and contrasted with other C4 systems, both single-celled and those in terrestrial plants, which are based on Kranz anatomy.
Abstract: Diatoms are responsible for at least a quarter of inorganic carbon fixed each year in the ocean. Despite very considerable research over the last 30 years, there are still a number of fundamental unresolved aspects of inorganic carbon assimilation by marine diatoms. It is not clear how the carbon-concentrating mechanism functions and whether it is based on the direct acquisition of inorganic carbon or on a C4 pathway, or a combination of both. Although evidence for the operation of a C4 pathway is accumulating, the role(s) of the enzyme(s) responsible for "C3 + C1" inorganic carbon assimilation in the light and dark are still matters of controversy. In this review, we discuss whether diatoms possess the enzymic and structural components necessary for a C4-type CO2-concentrating mechanism. These are compared and contrasted with other C4 systems, both single-celled and those in terrestrial plants, which are based on Kranz anatomy. New data are presented on expression of genes that might be involved in C4 ph...
100 citations
TL;DR: A new base for a more natural classification system in Cortinarius is proposed involving the taxonomic rearrangement of the species into the following major lineages that are informally designate as “clades” at this time.
Abstract: Phylogenetic relationships in the genus Cortinarius with emphasis on European species were studied by integrating a molecular phylogenetic analysis of nuclear rDNA sequences with morphological, che...
97 citations
TL;DR: It is found that some variation in DNA amount per genome copy distinguishes certain taxa, but ploidy-level estimates are at least as clear as the published chromosome counts, especially in the most common diploid-triploids-tetraploid range, and to the single published higher chromosome count, it is added evidence of pentaploids.
Abstract: Hawthorns and medlars are closely related genera in Rosaceae subfamily Maloideae, whose taxonomy remains poorly understood. Gametophytic apomixis occurs in polyploids, and diploids are sexual out-c...
TL;DR: One of the most notable contrasts between the photorespiratory pathway of higher plants and that of many of the green algae including Chlamydomonas reinhardtii lies in the enzymes that serve for ox...
Abstract: One of the most notable contrasts between the photorespiratory pathway of higher plants and that of many of the green algae including Chlamydomonas reinhardtii lies in the enzymes that serve for ox...
TL;DR: A combination of morphological and mo- lecular characterizations permitted integration of fungal strain identification with genetic relatedness among the isolates, thus allowing some inferences to be made on specificity of these endosymbionts under field conditions.
Abstract: To initiate a conservation program of the Orchidaceae from the Brazilian Atlantic rain forest with the purpose of ex situ conservation or reintroduction in the State of Minas Gerais, seven mycorrhi...
TL;DR: Direct measurements of CCM activity showed that internal CO2 : external CO2 ratio was down-regulated, and rates of photosynthesis decreased by approximately half over the same range of growth rates.
Abstract: Inorganic phosphate (Pi) plays a central role in cellular energy transduction. As a consequence, limitation of growth by phosphate availability can have an important impact on various aspects of metabolism. Since carbon acquisition via CO2-concentrating mechanisms (CCMs) in most microalgae is an active process, requiring ATP, it might be expected that phosphate limitation could have an indirect regulatory influence on CCM activity. We grew the green alga Chlorella emersonii Shihira et Krauss in semicontinuous or continuous cultures in nutrient-replete conditions or with orthophosphate as the limiting nutrient. CCM activity was down-regulated by P limitation. K0.5(dissolved inorganic carbon) values increased from approximately 4.5 µmol·L1 in cells growing at close to maximal rates to >12 µmol·L1 in cells growing at 0.2 d1. Maximal rates of photosynthesis decreased by approximately half over the same range of growth rates. Direct measurements of CCM activity showed that internal CO2 : external CO2 ratio ...
TL;DR: A model on how these two chloroplast CAs might participate in the CO2-concentrating mechanism of C. reinhardtii is presented, showing that Cah3 is 100 times more sensitive to sulfonamides than Cah6 and that Glp1, the γ-CA-like protein, does not have CA activity.
Abstract: Carbonic anhydrases (CAs) are zinc-containing metalloenzymes that catalyze the reversible interconversion of CO2 and HCO3. Aquatic photosynthetic organisms have evolved different forms of CO2-conc...
TL;DR: The hypothesis that burial in sand dunes is a major causative factor of zonation, which can extend beyond the foredunes and include com- munities of woody species is supported.
Abstract: The zonation of coastal dune plant communities from the beach to their inland margin is recognized world- wide; however, the cause of this pattern remains controversial because of the covariance of several environmental fac- tors, such as sand burial, salt spray, and microclimate, along a gradient perpendicular to the shoreline. To minimize the confounding influence of this complex shore-inland gradient and determine the direct effects of burial on plant com- munity composition, we examined stands along a burial gradient that extended parallel to the Lake Huron coastline, produced by variable blowout activity amongst a series of parabolic dunes comprising the second ridge inland from the coast. We used the point-quarter method an d1m×1mp lots toquantify overstorey and understorey plant communi- ties in each parabolic dune stand and determined species importance, here defined as the sum of density, frequency, and dominance for the overstorey and the sum of frequency and dominance only for the understorey. Correspondence analyses of the species importance - dune stand matrices elucidated a pattern of plant community composition on the primary ordination axis that was strongly related to an index of burial activity (r 2 = 0.40 and 0.87 for the overstorey and understorey, respectively). Burial was associated with changes in species richness and diversity, shifts in dominant species, and species replacement based on burial tolerance across the gradient. These data support the hypothesis that burial in sand dunes is a major causative factor of zonation, which can extend beyond the foredunes and include com- munities of woody species.
TL;DR: The marine microalga Dunaliella tertiolecta Butcher expresses a high affinity for dissolved inorganic carbon through a carbon-concentrating mechanism (CCM), known to be influenced by CO2 avai...
Abstract: The marine microalga Dunaliella tertiolecta Butcher expresses a high affinity for dissolved inorganic carbon (DIC) through a carbon-concentrating mechanism (CCM), known to be influenced by CO2 avai...
TL;DR: This is the first report regarding total phosphorus (P) and PA-P concentrations in scutellum and root-shoot axis portions of cereal embryos of WT in comparison to its matching lpa1-1 genotype.
Abstract: A comparison of mineral nutrient and phytic acid-phosphorus (PA-P) distribution in the grains of wild-type (WT) and low phytic acid1-1 (lpa1-1) corn (Zea mays L.) was conducted to determine how the...
TL;DR: This work examined seed dispersal phenology, germinability, and the spatial patterns of aerial seed rain, quantified the effects of soil surface relief, texture, and moisture on seed entrapment, and examined natural patterns of seedling emergence in relation to seed source proximity.
Abstract: Declines in riparian willow (Salix spp.) communities in Rocky Mountain National Park, Colorado, USA , coincident with a large increase in elk (Cervus elaphus L.) populations, has raised concerns about the future of willow communities. To identify possible constraints on willow establishment in two heavily browsed riparian areas, in 2000 and 2001, we examined seed dispersal phenology, germinability, and the spatial patterns of aerial seed rain, quantified the effects of soil surface relief, texture, and moisture on seed entrapment, and examined natural patterns of seedling emergence in relation to seed source proximity. All species dispersed seeds following peak streamflow and exhibited high germination rates (85%99%). Total seed rain differed between years, although broad spatial patterns were similar. Seed rain density as high as 7650 seeds/m2 occurred in reference areas but declined by over two orders of magnitude in heavily disturbed areas and by >90% within 200 m of seed sources. Seed entrapment rate...
TL;DR: Tillandsia recurvata L. is an atmospheric epiphyte that occupies tree canopies in many parts of tropical America and its host preferences are investigated by analyzing its occurrence on oak trees.
Abstract: Tillandsia recurvata L. is an atmospheric epiphyte that occupies tree canopies in many parts of tropical America. We investigated the host preferences of this species by analyzing its occurrence on...
TL;DR: Investigation of the relationships among lodging, stem anatomy, degree of stem lignification, and resistance to mycosphaerella blight in field pea found that disease severity was positively correlated with lodging scores of plants and lodging was negatively correlated with the proportions of supportive tissue.
Abstract: The relationships among lodging, stem anatomy, degree of stem lignification, and resistance to mycosphaerella blight (Mycosphaerella pinodes (Berk. & Blox.) Vestergr.) in field pea (Pisum sativum L.) were investigated in field experiments in Saskatchewan from 2000 to 2002. Disease severity, lodging resistance, plant height, internode length and diameter, and the cellulose, lignin, and fibre contents of stems were measured from 9 (2000) and 20 (2001, 2002) cultivars of field pea. Significant differences were observed in resistance to mycosphaerella blight and lodging among cultivars. In all years, ‘AC Tamor’ was among those cultivars with the highest disease ratings and lodging scores, whereas ‘CDC Striker’, ‘Carneval’, and ‘Integra’ were among those with the lowest ratings. Disease severity was positively correlated with lodging scores of plants. Lodging was negatively correlated with the proportions of supportive tissue (formerly parenchyma cells in the pith periphery, which have differentiated to sclere...
TL;DR: The contact points between positive-strand RNA plant viruses and their hosts, which are necessary for the translation and replication of the viral genomes, are discussed.
Abstract: Positive-strand RNA viruses constitute the largest group of plant viruses and have an important impact on world agriculture. These viruses have small genomes that encode a limited number of protein...
TL;DR: The exotic vine Vincetoxicum rossicum (Kleopow) Barbar is a major natural-areas pest throughout the Great Lakes Basin.
Abstract: The exotic vine Vincetoxicum rossicum (Kleopow) Barbar. (Asclepiadaceae) is a major natural-areas pest throughout the Great Lakes Basin. Colonization of new areas by this herbaceous perennial occur...
TL;DR: It is found that preservation of extensive arrays of transverse cortical microfilaments depends on unperturbed microtubule organization, and hitherto undescribed aspects of the Arabidopsis microfilament cytoskeleton that may provide important clues about mechanisms behind cell elongation are revealed.
Abstract: Determination of the precise role(s) of actin microfilaments in the control of cell shape and elongation in the root tips of the model genetic system Arabidopsis thaliana (L.) Heynh is frustrated by inadequate microscopy imaging techniques. In this paper, we documented both microfilaments and microtubules in the root tips of Arabidopsis by double immunofluorescence labelling and computer-generated reconstruction of confocal image series. Our procedure, which complements the use of recently developed fluorescent reporter proteins, revealed hitherto undescribed aspects of the Arabidopsis microfilament cytoskeleton that may provide important clues about mechanisms behind cell elongation. We found that preservation of extensive arrays of transverse cortical microfilaments depends on unperturbed microtubule organization. Compared with ordinary epidermal cells, cells situated in the trichoblast or hair-forming cell files were comparatively devoid of endoplasmic microfilaments when in the distal elongation zone,...
TL;DR: The number, distribution, and catalytic function of known and putative CAs and CA-like proteins from a variety of freshwater and marine cyanobacteria are examined.
Abstract: Carbonic anhydrases (CAs) are ubiquitous zinc metalloenzymes that catalyze the reversible dehydration of HCO3. These enzymes are encoded by at least five distinct, evolutionarily unrelated gene fa...
TL;DR: A combination of light microscopy (including differential interference contrast) and laser scanning confocal microscopy was used to document the colonization patterns of epidermal cells and details of intracellular hyphal complexes of five native ericaceous hosts as mentioned in this paper.
Abstract: A combination of light microscopy (including differential interference contrast) and laser scanning confocal microscopy was used to document the colonization patterns of epidermal cells and details of intracellular hyphal complexes of five native ericaceous hosts: Vaccinium oxycoccos L. (bog cranberry), Ledum groenlandicum Oeder. (Labrador tea), Vaccinium myrtilloides L. (velvet-leaf blueberry), Kalmia angustifolia L. (sheep laurel), and Gaultheria procumbens L. (wintergreen). Colonization patterns, hyphal complex morphology, and the structure of thick-walled epidermal cells varied considerably among hosts. Multiple hyphal connections were observed between adjacent epidermal cells, indicating that one fungal entry point may result in the colonization of more than one epidermal cell. Further field observations combined with fungal isolations from field-collected plants, identification, and reinoculation studies of other species in the large Ericaceae family are required to determine the full range of struc...
TL;DR: Results show that a weather cue triggers the cessation of reproduction in F. crenata, indicating that internal resource dynamics are important for mast seeding.
Abstract: To examine the proximate factors causing mast seeding in Fagus crenata Blume in Hokkaido, northern Japan, we analyzed a 13-year time series of seed production in relation to both previous reproduct...
TL;DR: Scanning transmission electron microscopy – energy-dispersive X-ray analyses of scutellum and aleurone layer globoids in both genotypes revealed that P, K, and Mg were the main mineral nutrients in globoids with low amounts of Ca, Fe, and Zn.
Abstract: Concentrations of P, phytic acid (myo-inositol hexakisphosphate, IP6), and other mineral storage elements were studied in wild-type and low phytic acid (lpa) genotype Js-12-LPA wheat (Triticum aest...
TL;DR: It is demonstrated that cycloheximide (an inhibitor of cytoplasmic protein synthesis) has no apparent effect on the initial induction of CO2-responsive genes, suggesting constitutive presence of all the molecular machinery needed by the cell to immediately respond to changes in CO2 levels.
Abstract: In numerous studies, the CIA5 gene of Chlamydomonas reinhardtii Dangeard has been shown to control the expression of several "CO2-responsive genes" when cells are shifted to higher or lower levels of CO2. Using DNA microarray analyses with arrays containing 2764 unique cDNA sequences, we have demonstrated that several additional genes are controlled by the CIA5 gene, some increasing in expression when CO2 levels are lowered and others decreasing. Not all genes that respond to changes in CO2 concentrations are controlled by CIA5. For example, the RH1 gene, is markedly induced when both wild-type and cia5 mutant cells are shifted to high levels of CO2. We demonstrate that cycloheximide (an inhibitor of cytoplasmic protein synthesis) has no apparent effect on the initial induction of CO2-responsive genes, suggesting constitutive presence of all the molecular machinery needed by the cell to immediately respond to changes in CO2 levels. This observation is consistent with our earlier suggestions that CIA5 or a...
TL;DR: In an effort to develop techniques for the characterization of the structure of β-carboxysomes, particularly the outer protein shell, a proteomic assessment of the Percoll-Mg 2+ carboxysome enrichment technique using the freshwater cyanobacterium Synechococcus sp.
Abstract: Carboxysomes are protein-bound, polyhedral microbodies within cyanobacteria, containing the key enzyme for photosynthetic CO2 fixation, ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco). Sequencing of cyanobacterial genomes has revealed that cyanobacteria possess one or other of two types of carboxysomes. Cyanobacteria containing form 1A Rubisco possess α-carboxysomes, while those with form 1B Rubisco possess β- carboxysomes. Given the central importance of carboxysomes in the CO2-concentrating mechanism of cyanobacteria, understanding the nature and composition of these structures is of considerable importance. In an effort to develop techniques for the characterization of the structure of β-carboxysomes, particularly the outer protein shell, we have un- dertaken a proteomic assessment of the Percoll-Mg 2+ carboxysome enrichment technique using the freshwater cyanobacterium Synechococcus sp. PCC7942. Both matrix-assisted laser desorption-ionization - time of flight mass spectrometry (MALDI-TOF MS) and multidimensional protein identification technology (MuDPIT) methods were used to determine the protein content of a novel carboxysome-rich fraction. A total of 17 proteins were identified using MALDI-TOF MS from enriched carboxysome preparations, while 122 proteins were identified using MuDPIT analysis on the same material. The carboxysomal protein CcmM was identified by MALDI-TOF MS as two distinct proteins of 38 and 58 kDa. The only other carboxysomal proteins identified were the large and small subunits of Rubisco (RbcL and RbcS). Reasons for the lack of evidence for the expected full complement of carboxysomal proteins and future di- rections are discussed.