The susceptibility of roots to infection by an arbuscular mycorrhizal fungus in relation to age and phosphorus supply

An apparatus in which plant roots may be challenged uniformly with inoculum of arbuscular mycorrhizal fungi is described. Seedlings of leek (Allium porrum L.) or clover (Trifolium repens L.) were first grown non-symbiotically in the apparatus for 21 d at three rates of phosphorus (P) addition to soil (1 50 (PI), 450 (P3) and 750 (P5) mg P kg-1 soil). The positions of individual root tips were recorded, and the root systems then challenged with inoculum of Glomus mosseae (Nicol & Gerd.) Gerdemann & Trappe. Roots were excised 14 d later, and the probability of occurrence of internal infection in successive 3 mm (clover) or 5 mm (leek) sections of root was estimated in first-order laterals (clover) or main axes (leek) from the proportion of sections at each location of replicate roots that bore internal fungal structures. Only in the region of a root proximal to the position of the root tips at inoculation could data be used to investigate change of probability of infection with cell age. Here, there were sharp declines in probability of infection with proximal distance, in both hosts and in all P treatments. The decline of probability was greater in clover: when expressed in terms of cell age at the time of challenge, there was no infection at Pl in cells > 10 d old in leek and none in cells > 7 d old in clover. Models of the form log(e) [p(i)/(1-p(i))] = alpha + beta x distance, where p(i) is the estimated probability of infection and alpha and beta are constants, were fitted to these data. The odds on infection are [p(i)/(1-p(i))]. For leek, 8 was unaltered by P addition (P3 and P5 curves were parallel to P1) but from alpha it could be calculated that on average the odds on successful infection at any particular distance were reduced by 3 7 % and 70 % by P3 and P5 rates of P addition respectively. In clover the curves for the three P treatments were not parallel. Addition of P appeared to reduce the odds on infection of clover much more than those of leek. We conclude that the simplest explanation for the patterns of infection in leek is that P addition increased the time taken for soil inoculum of G. mosseae to infect roots: the mechanism in clover might be more complex

The distribution of carbon and the demand of the fungal symbiont in leek plants with vesicular arbuscular mycorrhizas

RESP-893

Suprapubic Cartilaginous Cyst- A Case report

Suprapubic cartilaginous cyst (SPCC) is a rare condition known to occur in postmenopausal multiparous women. It is due to the degeneration of the pubic symphysis. Due to its slow progression and rarity in occurrence, it is often misdiagnosed. Presentation includes a painless mass in the suprapubic region, urinary retention, recurrent urinary tract infections, dysuria and dyspareunia. Knowledge of this condition is of great importance, as this is a benign condition that is managed conservatively, thereby avoiding unnecessary procedures. Surgical resection has not shown to have any additional benefit. Once suspected, MRI is ideal for diagnosis. This case report discusses a SPCC with punctuate calcifications and a locule of gas within it. This is the first documented case of a SPCC with punctuate calcifications

Quantitative evaluation of neuropharmacological trials

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116906/1/cpt1974153229.pd

Agronomic Management of Indigenous Mycorrhizas

Many of the advantages conferred to plants by arbuscular mycorrhiza (AM) are associated to the ability of AM plants to explore a greater volume of soil through the extraradical mycelium. Sieverding (1991) estimates that for each centimetre of colonized root there is an increase of 15 cm3 on the volume of soil explored, this value can increase to 200 cm3 depending on the circumstances. Due to the enhancement of the volume of soil explored and the ability of the extraradical mycelium to absorb and translocate nutrients to the plant, one of the most obvious and important advantages resulting from mycorrhization is the uptake of nutrients. Among of which the ones that have immobilized forms in soil, such as P, assume particular significance. Besides this, many other benefits are recognized for AM plants (Gupta et al, 2000): water stress alleviation (Augé, 2004; Cho et al, 2006), protection from root pathogens (Graham, 2001), tolerance to toxic heavy metals and phytoremediation (Audet and Charest, 2006; Göhre and Paszkowski, 2006), tolerance to adverse conditions such as very high or low temperature, high salinity (Sannazzaro et al, 2006), high or low pH (Yano and Takaki, 2005) or better performance during transplantation shock (Subhan et al, 1998). The extraradical hyphae also stabilize soil aggregates by both enmeshing soil particles (Miller e Jastrow, 1992) and producing a glycoprotein, golmalin, which may act as a glue-like substance to adhere soil particles together (Wright and Upadhyaya, 1998). Despite the ubiquous distribution of mycorrhizal fungi (Smith and Read, 2000) and only a relative specificity between host plants and fungal isolates (McGonigle and Fitter, 1990), the obligate nature of the symbiosis implies the establishment of a plant propagation system, either under greenhouse conditions or in vitro laboratory propagation. These techniques result in high inoculum production costs, which still remains a serious problem since they are not competitive with production costs of phosphorus fertilizer. Even if farmers understand the significance of sustainable agricultural systems, the reduction of phosphorus inputs by using AM fungal inocula alone cannot be justified except, perhaps, in the case of high value crops (Saioto and Marumoto, 2002). Nurseries, high income horticulture farmers and no-agricultural application such as rehabilitation of degraded or devegetated landscapes are examples of areas where the use of commercial inoculum is current. Another serious problem is quality of commercial available products concerning guarantee of phatogene free content, storage conditions, most effective application methods and what types to use. Besides the information provided by suppliers about its inoculum can be deceiving, as from the usually referred total counts, only a fraction may be effective for a particular plant or in specific soil conditions. Gianinazzi and Vosátka (2004) assume that progress should be made towards registration procedures that stimulate the development of the mycorrhizal industry. Some on-farm inoculum production and application methods have been studied, allowing farmers to produce locally adapted isolates and generate a taxonomically diverse inoculum (Mohandas et al, 2004; Douds et al, 2005). However the inocula produced this way are not readily processed for mechanical application to the fields, being an obstacle to the utilization in large scale agriculture, especially row crops, moreover it would represent an additional mechanical operation with the corresponding economic and soil compaction costs. It is well recognized that inoculation of AM fungi has a potential significance in not only sustainable crop production, but also environmental conservation. However, the status quo of inoculation is far from practical technology that can be widely used in the field. Together a further basic understanding of the biology and diversity of AM fungi is needed (Abbott at al, 1995; Saito and Marumoto, 2002). Advances in ecology during the past decade have led to a much more detailed understanding of the potential negative consequences of species introductions and the potential for negative ecological consequences of invasions by mycorrhizal fungi is poorly understood. Schwartz et al, (2006) recommend that a careful assessment documenting the need for inoculation, and the likelihood of success, should be conducted prior to inoculation because inoculations are not universally beneficial. Agricultural practices such as crop rotation, tillage, weed control and fertilizer apllication all produce changes in the chemical, physical and biological soil variables and affect the ecological niches available for occupancy by the soil biota, influencing in different ways the symbiosis performance and consequently the inoculum development, shaping changes and upset balance of native populations. The molecular biology tools developed in the latest years have been very important for our perception of these changes, ensuing awareness of management choice implications in AM development. In this context, for extensive farming systems and regarding environmental and economic costs, the identification of agronomic management practices that allow controlled manipulation of the fungal community and capitalization of AM mutualistic effect making use of local inoculum, seem to be a wise option for mycorrhiza promotion and development of sustainable crop production

The development of endomycorrhizal root systems VIII. Effects of soil phosphorus and fungal colonization on the concentration of soluble carbohydrates in roots

Concentrations of phosphorus in shoot and soluble carbohydrates (fructose, glucose, sucrose and fructans) in root were measured in non-mycorrhizal and vesicular-arbuscular (VA) mycorrhizal (Glomus mosseae) leek plants (Allium porrum) raised at six concentrations of soil phosphate. In conditions when an increased concentration of soil phosphate reduced VA mycorrhizal infection, the concentrations of soluble carbohydrates in the root were at a maximum. Therefore the hypothesis that greater concentrations of soluble carbohydrates in roots favour VA mycorrhizal infection is discounted. There was a specific effect of VA mycorrhizas, in that infected roots contained a larger concentration of sucrose than did uninfected roots, in plants with similar phosphorus concentrations in dry matter of shoots. We conclude, first, that increased phosphorus supply from either phosphate addition to soil or VA mycorrhizal infection increases concentration of soluble carbohydrates in leek roots and, secondly, that the VA mycorrhizal root behaves as a particularly strong physiological sink when there is an excess concentration of sucrose in the host