Search results for "PHLOEM"
showing 10 items of 23 documents
Vector Transmission of a Plant-Pathogenic Bacterium in the Arsenophonus Clade Sharing Ecological Traits with Facultative Insect Endosymbionts
2009
Bressan, A., Semetey, O., Arneodo, J., Lherminier, J., and BoudonPadieu, E. 2009. Vector transmission of a plant-pathogenic bacterium in the Arsenophonus clade sharing ecological traits with facultative insect endosymbionts. Phytopathology 99:1289-1296. The planthopper Pentastiridius leporinus (Hemiptera: Cixiidae) is the major vector of a nonculturable plant-pathogenic γ-3 proteobacterium associated with a disease of sugar beet called syndrome “basses richesses” (SBR). The bacterium, here called SBR bacterium, belongs to the Arsenophonous clade, which includes mostly insect-associated facultative symbionts. Assays using field-collected planthopper nymphs and adults were carried out to inve…
Genomics of intracellular symbionts in insects
2010
Endosymbiotic bacteria play a vital role in the evolution of many insect species. For instance, endosymbionts have evolved metabolically to complement their host's natural diet, thereby enabling them to explore new habitats. In this paper, we will review and give some examples of the nature of the metabolic coupling of different primary and secondary endosymbionts that have evolved in hosts with different nutritional diets (i.e., phloem, xylem, blood, omnivores, and grain). Particular emphasis is given to the evolutionary functional convergence of phylogenetically distant endosymbionts, which are evolving in hosts with similar diets.
Radio-metabolite analysis of carbon-11 biochemical partitioning to non-structural carbohydrates for integrated metabolism and transport studies.
2013
Metabolism and phloem transport of carbohydrates are interactive processes, yet each is often studied in isolation from the other. Carbon-11 ((11)C) has been successfully used to study transport and allocation processes dynamically over time. There is a need for techniques to determine metabolic partitioning of newly fixed carbon that are compatible with existing non-invasive (11)C-based methodologies for the study of phloem transport. In this report, we present methods using (11)C-labeled CO2 to trace carbon partitioning to the major non-structural carbohydrates in leaves-sucrose, glucose, fructose and starch. High-performance thin-layer chromatography (HPTLC) was adapted to provide multis…
Physiological,anatomical and biomass partitioning responses to ozone in the Mediterranean endemic plant Lamottea dianae
2011
Ozone effects on the perennial forb Lamottea dianae were studied in an open-top chamber experiment. Ozone was found to induce reductions in CO 2 assimilation and water use efficiency in the leaves of this species. These reductions were mainly related to a decline in the in vivo CO 2 fixation capacity of Rubisco (V c,max), rather than to stomatal limitations or photoinhibitory damage (F v:F m). In addition to chloroplast degeneration, other observed effects were callose accumulation, formation of pectinaceous wart-like cell wall exudates and phloem alterations. Moreover, ozone exposure significantly reduced root dry biomass. The possible relevance of these adverse effects for Mediterranean f…
Phloem and xylem flow contributions to nectarine fruit development
2021
This study aimed at determining how source-sink balance and phloem/xylem flows affect nectarine fruit growth during development. Different levels of water and assimilate availability to growing fruits were induced in vivo by varying leaf:fruit ratio (L:F) of fruiting shoots and by interrupting the phloem stream (girdling) at the base of entire fruiting shoots. Two fruiting shoots in each of six ‘Big Top’ adult nectarine trees were selected, labeled and their L:F was adjusted by thinning fruits or removing leaves to two levels: high L:F and low L:F. Stem water potential, stomatal conductance, continuous fruit diameter and leaf turgor pressure were measured before and after girdling at stage …
Cortical Bundles in the Persistent, Photosynthetic Stems of Cacti
1992
We examined 62 species in 45 genera of the cactus subfamily Cactoideae; all had collateral cortical bundles that permeated the broad, water-storing inner cortex and extended to the base of the outer, photosynthetic palisade cortex. Mean distance between cortical bundles was 0.75 mm, similar to the mean spacing (0.74 mm) of veins in leaves of Pereskia, a genus of relict leaf-bearing cacti. In 16 species, both young and extremely old stem cortex was available for study: in all of these, older bundles had larger amounts of phloem than did younger bundles, indicating that phloem had been produced for many years. In ten species, older bundles also had more xylem than younger bundles. In two gene…
Hormone directed sucrose transport during fruit set induced by gibberellins in Pisum sativum
1987
A new system has been developed to study hormone-directed transport in intact plants during parthenocarpic fruit set induced by gibberellins. Gibberellic acid (GA3) and gibberellin A1 (GA1) applied to unpollinated ovaries of pea (Pisum sativum L. cv. Alaska) promoted sucrose transport from the leaf to the site of hormone application. In vivo experiments showed an early (30 min) accumulation of [14C]-sucrose in ovaries of pea stimulated by gibberellins. This activation of sucrose transport appears to be mediated by gibberellins (GA1, GA3), increasing both loading of phloem with sucrose in the leaf (source) and sucrose unloading in the ovary (sink). The ability of pea tissue segments to take …
The syndrome "basses richesses" of sugar beet in France is associated with different pathogen types and insect vectors
2007
International audience; The syndrome “basses richesses” (SBR) of sugar beet in France is associated with two phloem-restricted uncultivable bacteria: a stolbur phytoplasma and a y-3 proteobacteria. The known vector of proteobacteria is a cixiid planthopper, Pentastiridius leporinus (Hemiptera Cixiidae), formerly shown to transmit both the prokaryotes. The role of P. leporinus and of two other planthopper species, Cixius wagneri and Hyalesthes obsoletus, in spreading the two pathogens to sugar beet were compared and quantified. Because of its abundance and high infection rates with proteobacterium, P. leporinus was confirmed to be the economic vector of SBR disease. P. leporinus and C. wagne…
Investigations on the Starch Content and Ultrastructure of Spruce Needles Relative to the Occurrence of Novel Forest Decline
1989
The starch content and ultrastructure of needles of Norway spruce trees [Picea abies (L.) Karst.] taken from three natural habitats, undamaged or with symptoms of novel forest decline, were investigated during the course of three years. The starch content was clearly dependent on the seasons, with a maximum in spring and a decline during summer and autumn, leading to a minimum in winter. Needles of damaged trees from one habitat exhibited in all three years from August to October a significantly higher starch content than their undamaged counterparts. Microscopic investigations of these needle samples exhibited severe damage symptoms to the phloem in macroscopically green needles, though mo…
Association with the Syndrome "Basses Richesses" of Sugar Beet of a Phytoplasma and a Bacterium-Like Organism Transmitted by a Pentastiridius sp.
2002
The syndrome “basses richesses” of sugar beet (SBR) was first observed in 1991 in Burgundy, France. A cixiid planthopper, Pentastiridius beieri, has been proved to be involved in the transmission to sugar beet of a stolbur phytoplasma, which could be detected in some affected plants. In 2000, periwinkle and sugar beet exposed to field-collected cixiids developed symptoms similar to SBR on sugar beet. Use of 4′-6-diamidino-2-phenylindole (DAPI) staining and transmission electron microscopy confirmed the presence of phytoplasma in some of the plants, which were also positive for this pathogen in a polymerase chain reaction (PCR) analysis. A phloem-restricted gram-negative bacteria was seen i…