Search results for "Systematics"
showing 10 items of 6702 documents
Genetic characterization of the nitrate reducing community based on narG nucleotide sequence analysis.
2003
The ability of facultative anerobes to respire nitrate has been ascribed mainly to the activity of a membrane-bound nitrate reductase encoded by the narGHJI operon. Respiratory nitrate reduction is the first step of the denitrification pathway, which is considered as an important soil process since it contributes to the global cycling of nitrogen. In this study, we employed direct PCR, cloning, and sequencing of narG gene fragments to determine the diversity of nitrate-reducing bacteria occurring in soil and in the maize rhizosphere. Libraries containing 727 clones in total were screened by restriction fragment analysis. Phylogenetic analysis of 128 narG sequences separated the clone famili…
Discovery and molecular characterization of a plasmid localized in Buchnera sp. bacterial endosymbiont of the aphid Rhopalosiphum padi
1995
We have identified and completely sequenced a novel plasmid isolated from the aphid Rhopalosiphum padi. Evidence which suggests that the plasmid occurs localized within the bacterial endosymbionts is presented. The plasmid contains the four genes that constitute the entire leucine operon. This fact makes it really unique since most plasmids are dispensable and lack genes that encode essential anabolic functions. Four more phloem-feeding aphid species also seem to contain homologous plasmids. Although further work is necessary, we hypothesize that this plasmid has appeared during the evolution of the symbiotic association between the aphid and the bacterial endosymbiont. The fact that this p…
Phylogeny and morphology of Hirsutella tunicata sp. nov. (Ophiocordycipitaceae), a novel mite parasite from Peru
2013
Abstract A new species of Hirsutella was isolated from unidentified mites on Petri plates inoculated with soil and root fragments collected from asparagus rhizosphere at Viru, Northern Peru. The fungus differs from other Hirsutella species by an envelope surrounding the conidium, conidia dimension and DNA sequences. In PDA cultures, the mycelium produced aerial hyphae with conidiogenous cells mainly at right angles, occasionally showing a secondary conidiophore. The solitary conidia are cymbiform, slightly apiculate, 5.0–6.0 × 3.0–4.0 μm. Phylogenetic analyses with partial rRNA and β-tubulin gene sequences confirmed the fungus as an Hirsutella (Ophiocordycipitaceae). Closest species shown b…
Conservation of optical purity of amino acids: a principal problem in biochemical and proto-biochemical systems.
1981
Dor L-amino acids, regardless of their state (peptide-bound or free, in the solid state or in aqueous solution), tend to racemize. In a living cell this racemization is usually compensated by specific degradation and replacement of the unwanted polypeptides that contain the wrong enantiomers. But a few long-lived proteins that are synthesized at or near birth are never replaced. Well investigated is the racemization of L-aspartic acid at a rate of 0.1 to 1.14 per cent per year in proteins from lenses and dentine. Increased racemization of eye lens proteins has been related to a form of human eye disease known as brunescent cataracts. Also quite well investigated is the racemization of amino…
EFFECT OF PLANT GROWTH REGULATORS AND ORANGE JUICE ON GROWTH OF CALLUS FROM FRUIT TISSUES OF WASHINGTON NAVEL ORANGE
1997
The effect of the plant growth regulators kinetin, gibberellic acid (GA3), and 2,4- dichlorophenoxyacetic acid (2,4-D), either alone or in combination with orange juice, on the in vitro growth of mesocarp and endocarp explants from 90–120 day-old Washington Navel Citrus sinensis orange fruits has been determined. Both fruit tissues formed callus. From endocarp 100% callus was formed in all cultures, even without growth regulators in the culture medium, while callus growth was lower from mesocarp. The addition of orange juice at a final concentration of 15% (v/v) to the basal medium without growth regulators increased the callus growth, specially that derived from endocarp. However, the high…
Hundreds of nuclear and plastid loci yield novel insights into orchid relationships.
2021
Pérez-Escobar, Oscar Alejandro, Dodsworth, Steven, Bogarín, Diego, Bellot, Sidonie, Balbuena, Juan A, Schley, Rowan J, Kikuchi, Izai A, Morris, Sarah K, Epitawalage, Niroshini, Cowan, Robyn, Maurin, Olivier, Zuntini, Alexandre, Arias, Tatiana, Serna-Sánchez, Alejandra, Gravendeel, Barbara, Torres Jimenez, Maria Fernanda, Nargar, Katharina, Chomicki, Guillaume, Chase, Mark W, Leitch, Ilia J, Forest, Félix, Baker, William J (2021): Hundreds of nuclear and plastid loci yield novel insights into orchid relationships. American journal of botany 108 (7): 1166-1180, DOI: http://doi.org/10.5281/zenodo.7778176
Pollination and reproductive success of two colour variants of a deceptive orchid, Dactylorhiza maculata (Orchidaceae)
2002
Polymorphism in petal colour is common in deceptively pollinated plant species. Most of the deceptively pollinated orchids are food frauds, and in most of them, the deception is not mimetic. These plants have conspicuously coloured flowers which they use as the main attractant of naive pollinators. In a field experiment, we studied the response of bumblebees and other types of flower visitors to colour differences between experimentally paired plants of Dactylorhiza maculata, a nectarless food-deceptive species. In addition, pollen removal, an estimate of male fitness, and fruit production, an estimate of female fitness, were measured in the two colour variants. We found a trend of bumblebe…
Position-dependent reproductive success of flowers in Dactylorhiza maculata (Orchidaceae)
2000
1. This study explores the importance of flower position for reproductive success of individual flowers of the deceptive terrestrial orchid, Dactylorhiza maculata (L.) Soo. 2. Upper flowers had smaller lips and produced lighter pollinia than those in other parts of the inflorescence, probably due to architectural effects. 3. Dry weight of seed capsules decreased from bottom to top in the inflorescence in both open-pollinated and hand-pollinated plants. However, removal of flowers from the middle and lowest parts of the inflorescence considerably increased seed production of the upper flowers. Decreased seed set was due to decreased resource availability because of the long maintenance time …
A new subspecies of Epipactis microphylla (Orchidaceae; Epidendroideae) from Pantelleria Island (Sicily)
2021
A new subspecies of Epipactis microphylla, proposed as subsp. cossyrensis is described and illustrated from Pantelleria, a volcanic island near Sicily. It differs from subsp. microphylla mainly in the shape and size of leaves and bracts and several floral traits. This taxon, previously attributed to E. pollinensis, a species currently treated as a synonym of E. purpurata, grows in the undergrowth of thermophilous woodlands occurring on the top of the island, where it numbers a few tens of individuals. The conservation status, phenology and taxonomic remarks are provided. Keys for the species belonging to the Epipactis atrorubens group (= subsect. Atrorubensae), including E. microphylla, are…
Deceptive pollination of Dactylorhiza incarnata: an experimental test of the magnet species hypothesis
1994
Floral deception, which mainly appears in highly evolved families such as Orchidaceae, was studied in Central Finland. In nectarless Dactylorhiza incarnata, the deceptive pollination system has been considered to function best in remote habitats such as marshes, where flowering plants attractive to pollinators are rare (remote habitats hypothesis). In contrast, the magnet-species theory predicts that a nectarless plant benefits from growing in the vicinity of nectarcontaining species. We tested these hypotheses by adding attractive, nectar-containg violets (Viola x wittrockiana) to orchid populations. The percentage of fruit set in D. incarnata was adversely affected by the violets, probabl…