Quality of Root Canal Obturation Performed by Senior Undergraduate Dental Students

The aim of the present study was to assess the quality of canal obturation performed by undergraduate denal students at Saveetha Dental College and Hospitals, Chennai. Records of 200 endodontically treated teeth from patients who were visited by undergraduate students between month of November 2014 to May 2015. Periapical radiographs of all treated teeth were assessed in terms of canal obturation quality (adequate density and length). Forty-five percent of teeth fulfilled the criteria of an acceptable root canal obturation. Adequate length and density of root filling was found in 89% and 34% of teeth, respectively. There was a significant difference between maxillary and mandibular teeth regarding the length of root canal obturation. A significant difference was observed between molars and other tooth types. The frequency of root canals with an acceptable filling was significantly greater in the anterior teeth compared to premolars or molars. The technical quality of root canal treatment performed by undergraduate dental students was found to be less than ideal

Root architecture of two sorghum varieties differ than drought stress tolerance : [Abstract, P 7.17]

Root architecture of two sorghum varieties, fitted in #Durra race# and with different response in drought conditions, has been studied on hydroponic system, pot and in situ on field. These varieties have similar aerial agro-morphological characteristics in optimal growth conditions. In pre-flowering drought stress condition, tolerant variety (SSM1611), has a stable and higher yield than the non-tolerant one (IS16101). On hydroponics conditions and pot growth, varieties are studied at young stage. On field, observations concerned the whole plant cycle. Frequent observations of the aerial system have been made in all the trials, with counting of emerged leaves number and measuring stem height. Adventitious roots number and adventitious roots ranks number have been daily observed on hydroponic system and observations was not destructive. Spatial root disposition on stem was observed on hydroponic condition. On pot and field, these observations were destructive and realised once a week. Adventitious root and their different regions growth (basal none branched region, branched region, apical none branched region) were studied in hydroponic system and in pot. The distribution of the root length density according depth in situ condition was studied using passage model from root impacts to length density. Results show that, the development and the growth of aerial system are practically similar for both of varieties whatever trials conditions. However, for the root system there are some differences in favour of the drought stress tolerant varieties (SSM1611). All the trials showed that, SSM1611 presents a higher adventitious roots number and adventitious roots ranks number than IS16101. Adventitious roots number per rank varies according to the rank and the variety. The distribution of the adventitious roots around the stem seems to be leaded by the same low. Adventitious root of the same rank are balanced distribution around the stem. Until three roots per adventitious root rank, adventitious roots of two successive ranks are distributed in a complementary way around the stem. The growth of adventitious roots and their different regions ((basal none branched region, branched region, apical none branched region)e) present similarity for both of varieties. On hydroponic system, adventitious root length increase first time and then stop their growth to maximal level. However in pot, adventitious root growth seems to bee unlimited. SSM1611 variety reveals a root length density according to depth more important than IS16101 variety one in field. Adventitious roots number, adventitious roots ranks number, and root length density could constitute pertinent and easily accessible drought stress tolerance criterions. (Texte intégral

Sowing Density: A Neglected Factor Fundamentally Affecting Root Distribution and Biomass Allocation of Field Grown Spring Barley (Hordeum Vulgare L.)

Studies on the function of root traits and the genetic variation in these traits are often conducted under controlled conditions using individual potted plants. Little is known about root growth under field conditions and how root traits are affected by agronomic practices in particular sowing density. We hypothesized that with increasing sowing density, root length density (root length per soil volume, cm cm−3) increases in the topsoil as well as specific root length (root length per root dry weight, cm g−1) due to greater investment in fine roots. Therefore, we studied two spring barley cultivars at ten different sowing densities (24–340 seeds m−2) in 2 consecutive years in a clay loam field in Germany and established sowing density dose-response curves for several root and shoot traits. We took soil cores for measuring roots up to a depth of 60 cm in and between plant rows (inter-row distance 21 cm). Root length density increased with increasing sowing density and was greatest in the plant row in the topsoil (0–10 cm). Greater sowing density increased specific root length partly through greater production of fine roots in the topsoil. Rooting depth (D50) of the major root axes (root diameter class 0.4–1.0 mm) was not affected. Root mass fraction decreased, while stem mass fraction increased with sowing density and over time. Leaf mass fraction was constant over sowing density but greater leaf area was realized through increased specific leaf area. Considering fertilization, we assume that light competition caused plants to grow more shoot mass at the cost of investment into roots, which is partly compensated by increased specific root length and shallow rooting. Increased biomass per area with greater densities suggest that density increases the efficiency of the cropping system, however, declines in harvest index at densities over 230 plants m−2 suggest that this efficiency did not translate into greater yield. We conclude that plant density is a modifier of root architecture and that root traits and their utility in breeding for greater productivity have to be understood in the context of high sowing densities

Nitrate and phosphate availability and distribution have different effects on root system architecture of Arabidopsis

Plant root systems can respond to nutrient availability and distribution by changing the three-dimensional deployment of their roots: their root system architecture (RSA). We have compared RSA in homogeneous and heterogeneous nitrate and phosphate supply in Arabidopsis. Changes in nitrate and phosphate availability were found to have contrasting effects on primary root length and lateral root density, but similar effects on lateral root length. Relative to shoot dry weight (DW), primary root length decreased with increasing nitrate availability, while it increased with increasing phosphate supply. Lateral root density remained constant across a range of nitrate supplies, but decreased with increasing phosphate supply. In contrast, lateral root elongation was suppressed both by high nitrate and high phosphate supplies. Local supplies of high nitrate or phosphate in a patch also had different effects. Primary root growth was not affected by a high nitrate patch, but growth through a high phosphate patch reduced primary root growth after the root left the patch. A high nitrate patch induced an increase in lateral root density in the patch, whereas lateral root density was unaffected by a high phosphate patch. However, both phosphate- and nitrate-rich patches induced lateral root elongation in the patch and suppressed it outside the patch. This co-ordinated response of lateral roots also occurs in soil-grown plants exposed to a nutrient-rich patch. The auxin-resistant mutants axr1, axr4 and aux1 all showed the wild-type lateral root elongation responses to a nitrate-rich patch, suggesting that auxin is not required for this response

Modelling diverse root density dynamics and deep nitrogen uptake — a simple approach

We present a 2-D model for simulation of root density and plant nitrogen (N) uptake for crops grown in agricultural systems, based on a modification of the root density equation originally proposed by Gerwitz and Page in J Appl Ecol 11:773–781, (1974). A root system form parameter was introduced to describe the distribution of root length vertically and horizontally in the soil profile. The form parameter can vary from 0 where root density is evenly distributed through the soil profile, to 8 where practically all roots are found near the surface. The root model has other components describing root features, such as specific root length and plant N uptake kinetics. The same approach is used to distribute root length horizontally, allowing simulation of root growth and plant N uptake in row crops. The rooting depth penetration rate and depth distribution of root density were found to be the most important parameters controlling crop N uptake from deeper soil layers. The validity of the root distribution model was tested with field data for white cabbage, red beet, and leek. The model was able to simulate very different root distributions, but it was not able to simulate increasing root density with depth as seen in the experimental results for white cabbage. The model was able to simulate N depletion in different soil layers in two field studies. One included vegetable crops with very different rooting depths and the other compared effects of spring wheat and winter wheat. In both experiments variation in spring soil N availability and depth distribution was varied by the use of cover crops. This shows the model sensitivity to the form parameter value and the ability of the model to reproduce N depletion in soil layers. This work shows that the relatively simple root model developed, driven by degree days and simulated crop growth, can be used to simulate crop soil N uptake and depletion appropriately in low N input crop production systems, with a requirement of few measured parameters

Response of starfruit shoot and root to varying rooting volumes

Shoot and root responses of root-pruned starfruit (Averrhoa carambola) seedlings in different rooting volumes, were studied using root observation chamber. Plant height and internode number were linearly correlated with rooting volumes over time, but stomata and epidermal cell number showed no response. Negative linear relationship was shown between the first-order root laterals and distant from root apex but root elongation had positive linear correlation with rooting volumes. Root length density, root surface area and total root length were significantly influenced by rooting volumes. However, there was no significant response on root tip density, coarse root length, percentage of dry matter distribution and root:shoot ratio. Leaf concentrations of N, P and Ca were significantly increased by rooting volumes but K and Mg were unaffected. A positive linear response between root elongation and plant height was observed

RACINE2: A software application for processing spatial distribution of root lenght density from intersections on trench profiles

A field method has been developed to quantify root length density (RLD) from root intersection density (RID) measured on a trench-profile, using modelling RID-RLD relationships. For 2D spatial distribution mapping of RID (at 5-cm scale for example), the large amount of data is processed and converted into RLD and root distances (ARD) through modeling. Calculations and RLD mapping can be performed quickly using a new freeware: RACINE2, tailored to this field method. The software also allows a simple modeling of potential root exploration ratio in the soil (PRER) taking ARD into account. The software contains published models calculating RLD from RID for several crops (maize, sorghum, sugarcane, rice), ARD from RLD and PRER from RD. Models may be changed or added into RACINE2. RLD, ARD and PRER are calculated for each spatial unit. They can be mapped. Data can be exported to a spreadsheet or a surface mapping software for further analysis. It is also possible to import data into RACINE2 from a spreadsheet. RACINE2 thus makes studies about root-soil interactions, root growth and root uptake easier. Some examples of field results calculated by RACINE2 are presented (RLD, ARD and RER profiles and maps). They point out differences of PRER when taking (or not taking) into account 2D spatial root distribution. Taking into account spatial variability of root system in relation with soil characteristics may be important for root water and nutrient uptake in field conditions. (Résumé d'auteur

Flory-Huggins theory for athermal mixtures of hard spheres and larger flexible polymers

A simple analytic theory for mixtures of hard spheres and larger polymers with excluded volume interactions is developed. The mixture is shown to exhibit extensive immiscibility. For large polymers with strong excluded volume interactions, the density of monomers at the critical point for demixing decreases as one over the square root of the length of the polymer, while the density of spheres tends to a constant. This is very different to the behaviour of mixtures of hard spheres and ideal polymers, these mixtures although even less miscible than those with polymers with excluded volume interactions, have a much higher polymer density at the critical point of demixing. The theory applies to the complete range of mixtures of spheres with flexible polymers, from those with strong excluded volume interactions to ideal polymers.Comment: 9 pages, 4 figure

Linking Aboveground Traits to Root Traits and Local Environment: Implications of the Plant Economics Spectrum.

The plant economics spectrum proposes that ecological traits are functionally coordinated and adapt along environmental gradients. However, empirical evidence is mixed about whether aboveground and root traits are consistently linked and which environmental factors drive functional responses. Here we measure the strength of relationships between aboveground and root traits, and examine whether community-weighted mean trait values are adapted along gradients of light and soil fertility, based on the seedling censuses of 57 species in a subtropical forest. We found that aboveground traits were good predictors of root traits; specific leaf area, dry matter, nitrogen and phosphorus content were strongly correlated with root tissue density and specific root length. Traits showed patterns of adaptation along the gradients of soil fertility and light; species with fast resource-acquisitive strategies were more strongly associated with high soil phosphorus, potassium, openness, and with low nitrogen, organic matter conditions. This demonstrates the potential to estimate belowground traits from known aboveground traits in seedling communities, and suggests that soil fertility is one of the main factors driving functional responses. Our results extend our understanding of how ecological strategies shape potential responses of plant communities to environmental change

Effect of drip irrigation and fertilization on tomato rooting patterns

Abstract Tomato rooting patterns, root length density (cm/cm3) and root length intensity (cm/cm2), were evaluated in a field trial with pot transplanted plants where three irrigation regimes (0.5, 0.7 and 1 ETm) and three nitrogen application levels: 50, 150 and 250 kg N/ha as Ca (NO3)2 were imposed. Root length was measured from soil-root samples taken with a hand auger, at three distances across the planting row (over the plant row, at 15 cm and 37.5 cm distance from the plant row) and on three dates during the growing season (34, 72 and 105 days after planting). Root length was recorded as root length density, RLD, cm/cm3 and total root length per unit of soil surface area, RLI, cm/cm2. Yield and ºBrix were estimated when about 80% of the fruits were red or orange. Irrigation and fertilization only in some occasions, locations and depths, had a significant effect on root length density. For all the sampling dates in the location over the plant row about 63 to 78 % of root length was concentrated in the top 10 cm of the soil profile. The results show that water applied increased significantly lateral root growth. Root length intensity in function of distance to the plant row was modelled for the three sampling dates. The soluble solid yield was greater in the treatment where the level of water applied was the highest. Differences found on commercial yield and ºBrix between fertilization treatments were not significant