3,398 research outputs found
Argyres-Douglas theories and S-duality
No full textThis article is distributed under the terms of the Creative Commons
Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are creditedM.B. and T.N. are partly supported by the U.S. Department of Energy under grants DOE-SC0010008, DOE-ARRA-SC0003883, and DOE-DE-SC0007897.
This research was supported in part by the National Science Foundation under Grant No.
NSF PHY11-25915. S.G. is partially supported by the ERC Advanced Grant “SyDuGraM”,
by FNRS-Belgium (convention FRFC PDR T.1025.14 and convention IISN 4.4514.08) and by the “Communaut´e Francaise de Belgique” through the ARC progra
Recommended from our members
Identification and characterization of an incomplete root hair elongation (IRE)-like gene in Medicago truncatula (L.) root nodules.
No full textCloning and molecular characterization of new genes constitutes a useful approach in studying the symbiotic interactions between the model plant Medicago truncatula and Synorhizobium meliloti. Large numbers of expressed sequence tags (ESTs) available for Medicago truncatula, along with numerous cDNA, oligonucleotides, and Affimetrix DNA microarray chips, represent useful tools for gene discovery. In an attempt to identify a new gene that might be involved in the process of nodulation in Medicago truncatula, preliminary data reported by Fedorova et al. (2002), who identified 340 putative gene products or tentative consensus sequences (TCs) expressed only in nodules, was used. This research was focused on TC33166 (TC103185), which has 3 ESTs in the TC, and whose strongest BLASTX hit of TC103185 is the incomplete root hair elongation (IRE) protein kinase-like protein (NP_192429) from Arabidopsis thaliana. The Arabidopsis IRE gene is required for normal root hair growth, and a role in apical growth was suggested (Oyama et al., 2002). Infection thread growth can be looked at as an inward growth of the root hair. Thus, TC103185 was a good candidate for identifying a gene that may be involved in early events of nodulation. MtIRE (GenBank accession AC122727) is organized in 17 exons and 16 introns, similarly to the Arabidopsis IRE gene. MtIRE is a new member of the IRE family and it is a putative Ser/Thr protein kinase. MtIRE is a nodule- and flower-specific gene, suggesting that nodulation may have recruited it from other developmental processes. MtIRE is likely to be involved in the invasion process, or in the maturation of the symbiosome, or of the cells that contain rhizobia, rather than infection thread initiation and elongation or in nitrogen fixation. Nodule invasion precedes the onset of MtIRE expression and the expression pattern changes in time within the nodule. RNA interference results support MtIRE expression data and suggest a possible role in preventing extensive defense responses. Our study demonstrates the existence of an Arabidopsis IRE homolog in Medicago truncatula root nodules with an entirely new function and regulation
Recommended from our members
Tests of a New Model of Paclitaxel-Induced Neuropathy and the Effects of Paclitaxel on the Dorsal Root Ganglia
No full textThis study examined a new model of paclitaxel-induced neuropathic pain and the effects of systemic paclitaxel on the gap junction protein subunit Cx43 and potassium inwardly-rectifying channel Kir4.1 within the dorsal root ganglia. In the new neuropathic pain model, subplantar injections of paclitaxel resulted in decreased conduction velocities of A-beta fiber compound action potentials in the sciatic (5.9%) and tibial nerves (6.8%) as well as in M (10.6%) and H (10.2%) waves. By using repeated recordings it was found that following paclitaxel injection, conduction velocities in the contralateral plantar nerve increased (9.2%). Systemic injections of paclitaxel resulted in reduced Kir4.1 immunolabeling in the dorsal root ganglia compared to vehicle injections. This reduction was observed in total labeling (32.4%) as well as in areas of intense labeling (28.7%). Reductions in overall Cx43 immunolabeling (25%) and area (25%) following systemic paclitaxel injections were not statistically significant. The results of these studies suggest that subplantar injections of paclitaxel can result in reduced peripheral nerve conduction velocities. The results also show that a unilateral neuropathy can result in contralateral changes in conduction velocities. The effects of paclitaxel on reducing Kir4.1 levels suggest that neuropathic pain caused by paclitaxel may share mechanisms in common with other types of neuropathies which show similar changes in Kir4.1 levels
Response of Root Properties to Tripartite Symbiosis between Lucerne (Medicago sativa L.), Rhizobia and Mycorrhiza Under Dry Organic Farming Conditions
No full textIt is generally considered that root turnover is a major contributor to organic matter and mineral nutrient cycles in organic managed agroecosystems. Approach: This study designed to investigate whether microbial activity could affect on root properties of lucerne in an organically managed field under dry weather conditions. The trial was laid out as a factorial experiment in the fields of the University of Natural Resources and Applied Life Sciences, Vienna-Austria at Raasdorf in 2007. The experimental factors of Sinorhizobium meliloti and arbuscular mycorrhiza (AM) including Glomus etunicatum, G. intraradices and G. claroideum and irrigation levels were tested. Results: Results showed that increasing water deficit affected root dry weigh, specific root mass and root length significantly at 1% level and co-inoculation of rhizobium and mycorrhiza with irrigation could increase all root parameters. Data’s of variance analysis for mycorrhizal colonization showed that main effect of using mycorrhiza had significant effects on root parameters at 5% and 1% probability level in first and second harvest, respectively. Results of mean comparisons by Duncan’s multiple range test showed that mycorrhizal colonization was higher in the inoculated treatments by rhizobium , mycorrhiza and irrigated plots in both harvests. Double interaction of mycorrhiza and irrigation was higher in both harvests (37.05% and 65.73%, respectively). Conclusion: Hence, it can be suggested that the tripartite symbiosis of S. meliloti, AM and lucerne can improve the performance of lucerne in organic farming and under dry conditions. Such traits could be incorporated into breeding programs to improve drought tolerance especially in organic fields
Recommended from our members
Root initiation and elongation in Douglas-fir, Pseudotsuga menziesii (Mirb.) franco, stem cuttings as related to bud and cambial activity
No full textThe relation of bud and cambial activity to root initiation and
elongation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)
stem cuttings was studied through two successive growth cycles.
Stem cuttings of current season's growth were taken periodically
from field-grown Douglas-fir trees to determine: (1) origin and
development of root initials; and (2) controlling factors in bud and
cambial activity and subsequent rooting in this species. Growth
chambers were used to control photoperiod, air temperature, and
relative humidity, and propagation benches and portable trays were
employed to control the temperature of the rooting medium.
Anatomical studies showed that callus originates principally
from the vascular cambium, but phloem and xylem parenchyma may
also contribute. Differentiation within callus led to the formation
of spirally oriented root initials having no connection with the main
vascular system. Continuous cell division, differentiation, and
subsequent distal elongation of root initials gave rise to root primordia
having complete vascular connections with the stem axis. Once
root primordia initiated, elongation occurred within 15 to a maximum
of 30 days. There was no apparent difference in origin of
adventitious roots in cuttings taken at various stages of shoot development.
Long photoperiods (18 hr) exerted a profound influence on bud
and cambial activity and enhanced rooting over that of short photoperiods
(9 hr). This response to photpperiod was modified by stage
of shoot development and rooting medium temperature. LD enhancement
of rooting was most pronounced before and during bud dormancy,
but following bud dormancy cuttings rooted equally well under SD.
Cuttings rooted significantly better under 26° (12.95%) and 18°C
(11.91%) rooting medium temperatures than under 10°C (1.13%).
The cambium of Douglas-fir showed no endogenous dormancy,
and cell division in cambium was not a limiting factor in rooting.
Auxin treatment significantly increased rootability during pre- and
post-dormancy. During true dormancy, auxin treatment alone was
not effective in stimulating rooting, and LD or cold treatment was
required. Chilling requirement for rooting was considerably less
than that for breaking bud dormancy. Cuttings with good callus often
failed to root, but many cuttings with only fair callus showed root
initiation and elongation, suggesting that root initiation in Douglas-fir
is not directly related to the extent of callus formation, but
rather to a hormonal balance necessary for differentiation within
callus. There was no relationship of cambial activity and cutting
rootability to the presence or absence of buds, probably indicating
that leaves alone are capable of supplying the growth substances
needed for cambial activity and root initiation in Douglas-fir
Recommended from our members
Physiological control of fine root turnover in Douglas-fir
No full textTo determine whether shading increases drought-induced
root mortality by changing the chemical
composition of roots, I conducted an experiment in which
high and low light treatments in combination with high
and low soil moisture treatments were applied to
seedlings of Douglas-fir (Pseudotsuqa menziesii Mirb.
Franco). Because synthesis of suberin (a water-repellent
compound found in roots) is metabolically expensive, I
hypothesized that suberin synthesis might be reduced in
roots of a shade-stressed tree and thereby, susceptibility
to desiccation would be increased. As expected,
the drying treatments increased root mortality for the
shaded seedlings, however, no differences in suberization
were found. I measured starch and sugar concentrations
of the roots and found that carbohydrate reserves of
roots in the shaded treatments were nearly exhausted. I
concluded that root mortality induced by shading and
drought was probably caused by depletion of carbohydrate
reserves in the root rather than by differences in
resistance to desiccation.
I then set up an experiment to determine whether
accumulation and depletion of carbohydrate reserves were
indeed the physiological mechanisms underlying fine root
turnover. Douglas-fir seedlings were grown at soil temperatures
of 10°C, 20°C, and 30°C, at uniform air
temperatures, with and without light. It was necessary to
develop a starch extraction procedure using 35%
perchloric acid in order to consistently extract all
starch from the tissue. Sequential harvests were weighed
and analyzed for starch and sugars. Starch reserves were
exhausted in the roots of the dark-grown seedlings at all
temperatures and were also exhausted in the roots of the
light-grown seedlings at 20°C and 30°C. In the light-grown
seedlings from the 10°C treatment, however,
significant accumulations of starch were observed in
association with pulses of root growth. Based on this
study and on others from Sweden and from Oregon, I
suggest that root lifetimes may be determined by the
amount of starch with which a newly grown root is endowed
and the rate at which this starch supply is respired. A
simple means of estimating root biomass production and turnover based on root starch and soil temperature is
described
Root chemistry of Douglas-fir seedlings grown under different nitrogen and potassium regimes
No full text Root chemistry and biomass allocation of Douglas-fir (Pseudotsuga menziesii var. glauca (Bessn.) Franco) seedlings under optimal and deficient levels of nitrogen (N) and potassium (K) were studied. Seedlings receiving high-N treatments were significantly larger and allocated more dry matter to their stems and less to their roots than those receiving the low-N treatments. The K treatments did not significantly affect total seedling biomass or root/shoot ratios. Root tip starch concentrations were significantly higher and root tip sugar concentrations were lower in plants receiving the low-N treatments. Seedlings receiving the high-N, low-K treatment had significantly lower concentrations of phenolics and tannins and lower ratios of these compounds to sugars in the root tips than seedlings receiving the high-K treatments. Samples taken from two locations on the root system show that concentrations of phenolics, tannins, sugars, and starches were substantially higher in the root collar than in the root tips. Because of lower within tissue variation, we recommend sampling at root tips to better detect treatment differences. This study shows that N levels affect starch concentrations in the roots, while K levels affect root phenolic and tannin concentrations. Possible relationships between low root phenolic and tannin concentrations and lessened resistance of Douglas-fir to root disease are discussed. </jats:p
Intraspecific Fine-Root Trait-Environment Relationships across Interior Douglas-Fir Forests of Western Canada
No full textVariation in resource acquisition strategies enables plants to adapt to different environments and may partly determine their responses to climate change. However, little is known about how belowground plant traits vary across climate and soil gradients. Focusing on interior Douglas-fir (Pseudotsuga menziesii var. glauca) in western Canada, we tested whether fine-root traits relate to the environment at the intraspecific level. We quantified the variation in commonly measured functional root traits (morphological, chemical, and architectural traits) among the first three fine-root orders (i.e., absorptive fine roots) and across biogeographic gradients in climate and soil factors. Moderate but consistent trait-environment linkages occurred across populations of Douglas-fir, despite high levels of within-site variation. Shifts in morphological traits across regions were decoupled from those in chemical traits. Fine roots in colder/drier climates were characterized by a lower tissue density, higher specific area, larger diameter, and lower carbon-to-nitrogen ratio than those in warmer/wetter climates. Our results showed that Douglas-fir fine roots do not rely on adjustments in architectural traits to adapt rooting strategies in different environments. Intraspecific fine-root adjustments at the regional scale do not fit along a single axis of root economic strategy and are concordant with an increase in root acquisitive potential in colder/drier environments.Forest and Conservation Sciences, Department ofReviewedFacult
A ROOT-ROT OF DOUGLAS FIR CAUSED BY <i>PORIA WEIRII</i>
No full text A laminated root-rot of Douglas fir [Pseudotsuga taxifolia (Lamb.) Britt.] occurs in young stands on Vancouver Island, B.C. The decay, the sporophore associated with it, and the cultural characters of the fungus are described A comparison with Poria Weirii Murr., previously reported only on Thuja plicata (D Don.), shows a close resemblance in all respects between the two fungi. </jats:p
Recommended from our members
Incidence of root pathogens on Douglas-fir within the Reuben's Reserve, Nez Perce Indian Reservation, Idaho
No full textRoot diseases were evaluated on the Reuben's Reserve, Nez Perce Indian Reservation, Idaho. Nineteen trees adjacent to two suspected root disease centers were pushed with a D-6 tractor to expose their root systems. Extent of root necrosis and decay was determined and related to level of crown thinning, chlorosis, and dieback. All excavated trees were infected with Phaeolus schweinitzii; some trees with severe root deterioration lacked crown decline symptoms typical of root disease. Evidence of insect activity was often found in the root crown or bole of trees with extensive root necrosis and decay. A black staining organism, Verticicladiella antibiotica, was isolated from roots of two trees. Implications of root diseases in management of Douglas-fir in the Reserve are discussed
- …
