Root Decay Research Articles

Turnover rates of roots vary considerably across temperate forage species

Plant specialized metabolites (PSMs) have been found to reduce the activity of soil microorganisms lowering the decay rates of plant residues, which might positively affect C sequestration. Several PSM are produced by temperature forage species, but the impact of those material on decomposition has primarily been studies in forest ecosystems. Thus, the objective of this study was to i) quantify the relevant PSMs contained in the aboveground and belowground parts of forage species, ii) identify differences in CO2-emissions resulting from the root turnover of those species, and iii) identify the main chemical root properties that affect the CO2-emissions resulting from the root turnover. Eight cultivars of five forage species were grown in pots in a greenhouse. Aboveground- and belowground biomass was harvested and proanthocyanidins (PAs) and other PSMs (alkaloids and flavonoids) were measured. Afterwards, the roots were incubated for 58 days to investigate the root turnover while the CO2-emissions by the decay of roots from the soil were measured. Results showed i) PA concentrations varied widely among the species (7.8–45.6 mg PA g−1 dry matter (DM)), as well as between above- and belowground biomass; ii) that CO2-emissions differed significantly in terms of dynamics and the amount (15–40% of added C); and iii) that none of the measured root chemical properties could sufficiently explain the variance in CO2-emissions. Nevertheless, the almost three-fold range in turnover rates shows great potential for the future in terms of specifically designing temperate grasslands via species selection to enhance potential carbon sequestration.

Long-term modelling of soil N mineralization and N fate using STICS in a 34-year crop rotation experiment

Net soil N mineralization is a driver for N uptake and N losses at an annual scale, but is itself dependent on long-term N surplus and C-N storage in agricultural systems. The accurate modelling of N mineralization remains challenging. Thus, the STICS research version V1610 that includes modified soil organic nitrogen (SON) mineralization and root biomass turnover modules was assessed in this study regarding its predictions of net N mineralization and long-term N fate in a 34-year experiment comparing crop rotations with or without catch crops (CC) and bare soil. The in situ gross balance method was used as a reference to estimate net N mineralization based on measured N variables (i.e. N uptake, exported N and N leaching). The Index of Agreement (IA) of STICS predictions concerning crop biomass, crop yield, N uptake and exported N ranged between 0.61 and 0.76, 0.79–0.89, 0.49–0.64 and 0.47–0.58, respectively, depending on the crop rotations. STICS also enabled a good simulation of annual drainage and N leaching with IA ranges of 0.92–0.96 and 0.78–0.93, but high leaching values were not captured by the model. The STICS research version simulates the decay of deep roots (below a depth of 25 cm) but it neglects their decomposition. This simplification could cause an underestimation of N leaching. The observed N surplus ranged from 27 to 51 kg N ha−1 yr−1 in the cropped rotations depending on the crop rotations, and the N surplus was accurately simulated with an IA of 0.75–0.84. STICS produced a good prediction of changes in SON stocks under cropped rotations and bare soil, with both the rRMSE and rMBE being lower than 10%. Estimated mean annual N mineralization was 115 kg N ha−1 under cropped rotations and 42 kg N ha−1 under the bare soil treatment. STICS relatively well predicted net N mineralization regarding both differences between crop rotations and over time. Moreover, STICS correctly simulated the long-term effects of CC on drainage, N leaching, SON accumulation and net N mineralization. To conclude, STICS is a useful model to predict net N mineralization and N fate in long-term crop rotations. Moreover, this work raised new questions concerning the long-term fate of N stored in deep dead roots. Further improvements to describe the fate of these residues should enhance the prediction of N leaching by the STICS model and enable the optimization of N management in cropping systems.-

Anthropogenic N deposition alters soil organic matter biochemistry and microbial communities on decaying fine roots.

Fine root litter is a primary source of soil organic matter (SOM), which is a globally important pool of C that is responsive to climate change. We previously established that ~20years of experimental nitrogen (N) deposition has slowed fine root decay and increased the storage of soil carbon (C; +18%) across a widespread northern hardwood forest ecosystem. However, the microbial mechanisms that have directly slowed fine root decay are unknown. Here, we show that experimental N deposition has decreased the relative abundance of Agaricales fungi (-31%) and increased that of partially ligninolytic Actinobacteria (+24%) on decaying fine roots. Moreover, experimental N deposition has increased the relative abundance of lignin-derived compounds residing in SOM (+53%), and this biochemical response is significantly related to shifts in both fungal and bacterial community composition. Specifically, the accumulation of lignin-derived compounds in SOM is negatively related to the relative abundance of ligninolytic Mycena and Kuehneromyces fungi, and positively related to Microbacteriaceae. Our findings suggest that by altering the composition of microbial communities on decaying fine roots such that their capacity for lignin degradation is reduced, experimental N deposition has slowed fine root litter decay, and increased the contribution of lignin-derived compounds from fine roots to SOM. The microbial responses we observed may explain widespread findings that anthropogenic N deposition increases soil C storage in terrestrial ecosystems. More broadly, our findings directly link composition to function in soil microbial communities, and implicate compositional shifts in mediating biogeochemical processes of global significance.

Root order and initial moisture status influenced root decomposition in a subtropical tree species Liquidambar formosana

Root decomposition plays an important role in biogeochemical cycles in terrestrial ecosystems. However, there is still controversy on whether low-order (finer) or high-order (coarser) roots decay faster. Previous studies on root decomposition often used dried root samples, and the dehydrating process may influence the results. In this study, we aimed to examine the decomposability of low- and high-order roots and whether initial moisture status would influence their decomposition. We carried out a one-year litterbag experiment for roots of a subtropical tree species Liquidambar formosana. Roots for the decomposition were divided into low- (1st and 2nd orders) and high-order (3rd and 4th orders) classes, and were dried or kept fresh before being buried into the soil. We found that low-order roots were decomposed slower (half the rate of high-order roots in terms of mass loss), and the content of soluble carbohydrates was the main influencing factor. We also found that drying prior to decomposition facilitated the decomposition of high-order roots during the early stage by 10%. Our study suggests that litter carbon quality, particularly soluble carbohydrate content, is the major driver for root decomposition, and that previous studies using dried root samples might have overestimated short-term root decomposition.

The Design of Temperature and Soil Humidity Control with Fuzzy Method on Greenhouse for Red Chilli Pepper Seedling

The ideal soil temperature and humidity in red chilli pepper seedling is very important in the growth of the plant. The cultivation of red chili plants in greenhouses is very good, because the environment in greenhouses can be manipulated according to the needs of the plants. The ideal temperature for red chili breeding is 25oC to 27oC, for soil moisture drainage and aeration must be maintained during growth. Red pepper plants can grow well in moisture 50% to 70%, irregular soil moisture can cause rooting disease and root decay in plants. Cultivation of plants in greenhouses can maintain the nursery process, because the plants can be cultivated in accordance with the Operational Procedure Standards (SOP). Generally the farmers in breeding of red pepper is done in a trational way. In the process of temperature control and soil moisture using fuzzy method where the system can work automatically, which can facilitate the work of farmers in seeding plants from uncertain environmental conditions outside. In the measurements that have been done can be taken conclusion percentage error mean temperature from setpoint which have been set at the time in the morning equal to 2,48%, at noon equal to 9,79% and at night equal to 1,93%. Then each addition of 1 second watering, soil humidity rise up to 0.067%.

Rootstock breeding for resistance to grapevine decline and dieback in southern Brazil

Grapevine decline and dieback is a serious problem for grape production in southern Brazil. It is characterized by a set of symptoms that lead to the weakening and death of affected plants. The main causes are a root scale, the ground-pearl (Eurhizococcus brasiliensis), associated with soil fungi (Cylindrocarpon, Fusarium, Phaeacrimonium and others), and high-clay-content soils. Apparently, the root wounds caused by ground-pearl under poorly aerated soil conditions allow the entrance of root decay fungi, resulting in plant death. The creation of grape rootstocks resistant to root decay fungi is one objective of the grape breeding program at Epagri, the Agricultural Research Enterprise of Santa Catarina State, Brazil. The first step was the identification of resistance sources. In rootstock trials carried out in areas where high mortality rates were previously observed, all traditional rootstocks were highly susceptible. Vitis caribaea hybrids showed a high level of resistance but also some defects, such as excessive vigor and absence of winter dormancy. Some genotypes of Vitis shuttleworthii and Vitis palmata, originating from the waterlogged soil conditions of the Everglades (Florida, USA), also showed a high level of resistance. However, the performance of these genotypes and their descendants under dry soil conditions was very poor, and more generations of crossing will be necessary to eliminate undesirable characters. The most promising breeding lines resulted from self pollination of the rootstock IAC 572 (V. caribaea × 101-14Mgt). The selection process started from 840 seedlings and resulted in 23 selections that showed no symptoms of vine decline at three different sites. These selections are being evaluated now for productivity and fruit quality in rootstock trials with different scion cultivars.

Soil water response of plant functional groups along an artificial legume grassland succession under semi-arid conditions

Drought can cause and accelerate the degradation of planted legume grassland, and the changes in plant community composition can further influence soil physical properties. Here, the soil water response of different plant functional groups (legumes, grass, and forbs) were studied along a legume grassland degradation succession according to the above-ground biomass and the proportion of each functional group. In particular, changes in the soil water storage (SWS), soil properties (soil capillary porosity (CP), and soil organic matter) and plant traits (proportion of functional groups and below-ground biomass) were quantified in a continuously cultivated legume grassland for fifteen, sixteen, eighteen, and twenty-two years, without any tillage. The experimental plots were located in the semi-arid region of the Chinese Loess Plateau, in a flat area without runoff contribution. All plant and soil samples, and measurements, were obtained in a few days to minimize the temporal variability. SWS increased at 50–150 cm soil depth when the proportion of legume functional group (LFG) decreased from 70% to 5%, and this increment was ca. 20% at 50–100 cm soil layers. The Shannon-Wiener diversity index (H), the species richness (R), LFG, CP, and the non-capillary porosity (NCP) were significantly correlated with SWS (P < 0.05). The infiltration capacity significantly improved when the proportion of LFG accounted for 5%, which favored the recharge of the soil water reservoir with rainfall. Roots decay apparently improved the soil structure, and favored water infiltration, providing a suitable condition for latter vegetation growth. This study underlined the significant interaction that exists between the plant functional groups and the soil water processes during the artificial legume grassland succession. We proved that plant composition can change the surface hydrologic cycle, and the soil water exchange, in rainfed grassland.

Oral health assessment of independent elders in Texas.

The oral health status of older adults in North Texas is largely unknown. This cross-sectional, pilot study used the Basic Screening Survey for older adults involving a self-administered questionnaire and oral screening examination of 155 adults aged 65 years and older, in four Dallas, TX settings, stratified socioeconomically. Recruitment occurred from July 2012 through March 2014. Participants were between 65 and 90 years of age. The sample was predominantly female (64%), reflecting Texas population diversity with 49.7% White, 34.2% Hispanic, 14.2% Black, and 1.8% others. Missing teeth number (P<.019), functional contacts, untreated decay, root decay (P<.05), tooth mobility, root fragments and need for emergency treatment (P<.021) differed significantly regarding site and ethnicity. Participants at the least affluent sites (two) evidenced significant unmet dental needs and suboptimal access to care. In contrast, those at the most affluent sites (also oldest participants) had good oral health and access to care. There are profound oral health disparities in urban North Texas based on socioeconomic status. These findings suggest that poor oral health is not inevitable in the elderly, as long as there is access to care. Larger-scale studies are required to broadly address oral health disparities among elderly Texans.

Ruzigrass root persistence and soybean root growth

Cropping systems using forage grasses as cover crops have been effective in soil conservation and nutrient cycling, but root persistence of ruzigrass (Urochloa ruziziensis) is significant, and may impair root growth of the next crop. However, it is unknown how this would interfere with soybean root growth and yield under field conditions. Ruzigrass root persistence during soybean development, and its effects on soybean yield were studied under field conditions. Ruzigrass and soybean were grown alone or in rotation, and roots were sampled every 30 days and evaluated using carbon isotope discrimination. Despite temporary impairment of soybean root growth in the uppermost soil layer, there was no effect of ruzigrass on soybean yield. The ruzigrass root decay rate was high in the first 30 days after desiccation, and then it slowed down. Soybean roots grew slowly up to 30 days after planting (DAP, V7) and then peaked at 90 DAP (R5). Soybean root growth and yield are not affected by decaying ruzigrass roots. Around 50% of the ruzigrass roots are mineralized before soybean flowering. However, by soybean harvest there are still from 25 to 28% of non-decomposed ruzigrass roots up to the soil depth of 0.20 m.

Modelling effects of root growth and decay on soil water retention and permeability

Plant roots can change the soil water retention curve (SWRC) and saturated permeability (ksat) of vegetated soils. However, there is no model that could capture both the effects of root growth and root decay on these soil hydraulic properties simultaneously. This note proposes a new void ratio function that can model the decrease and increase in soil void ratio due to root occupancy (upon growth) and root shrinkage (upon decay), respectively, in an unsaturated vegetated coarse-grained soil. The function requires two root parameters; namely, root volume ratio and root decay ratio, both of which can be readily measured through root excavation and image-based analysis. The new function is incorporated into a void ratio–dependent SWRC model for predicting the SWRC of vegetated soils. Similarly, the same function can be combined with the Kozeny–Carman equation for predicting ksat. The model prediction is then compared with a set of new field test data and an existing laboratory dataset for a silty sand vegetated with plant species under the family Schefflera. Good agreements are obtained between the measurements and predictions.

Genome Resource for Neocamarosporium betae (syn. Pleospora betae), the Cause of Phoma Leaf Spot and Root Rot on Beta vulgaris.

Neocamarosporium betae (syn. Phoma betae, Pleospora betae) is the cause of Phoma leaf spot and root decay on Beta vulgaris worldwide. Despite the economic importance of the pathogen, many aspects of its life cycle and population biology remain unknown. The first genome assembly of N. betae was constructed to facilitate identification of mating-type loci and development of microsatellite markers for population genetics studies. The de novo assembled genome is provided as a resource for future genetic studies to understand the genetic mechanisms underlying disease development and host-pathogen interactions.

Radiocarbon age discrepancies between the carbonate cement and the root relics of rhizoliths from the Badain Jaran and the Tengeri deserts, Northwest China

Carbonate rhizolith is one of mineral encrustations of plant roots. The radiocarbon (14C) dates and stable carbon isotopes of rhizoliths are widely used to study geochronology, paleoclimate, paleoecology and paleoenvironment changes. However, due to a few available comparisons of 14C dates of the carbonate cement and the plant root relics within the same rhizoliths, the carbon sources that form rhizolith cements are largely unknown. Here, we present accelerator mass spectrometry (AMS) 14C dates of carbonate cement and the plant root relics within the same rhizoliths from dune surface soils in the Badain Jaran and the Tengeri deserts, Northwestern China. The modern dead plant roots and bulk soil carbonates nearby were also dated. It is found that the root relics range from 1825 CE to 1983, while the carbonate cements of the rhizoliths have ages from ~6,900 to ~4,700 calibrated years before present (calBP). The ages of the bulk soil carbonates vary from 18,700 to 35,300 and 39,300 calBP, revealing complicated soil carbonate matrix. The results suggested that the carbon sources for the carbonate cements of the rhizoliths were derived mainly from ancient soil carbonates with a small contribution from dead plant roots and a minor contribution from lithogenic carbonates. Mass balance of stable carbon isotopes was used to calculate the proportional contribution of the carbon from ancient soil carbonates and plant roots relics. After subtracting the modern carbon contribution from the decomposed plant roots in fraction of modern carbon (F14C), the mass balance estimated that the ancient soil carbonates were formed within 7,750–5,000 calBP, about 850–300 years older than obtained rhizolith cement ages. It is proposed that dead roots decay triggered the rhizoliths formation by releasing CO2 to form acid media with free HCO31−/CO32– ions, which caused dissolution of the old soil and lithogenic carbonates in soil matrix. Carbonate recrystallization took place to form rhizoliths tubes around the dead roots. Detailed age discrepancies between rhizolith cements and dead root relics provide new insight for better understanding the dynamics of the rhizolith formation and associated implications for paleoenvironment reconstructions.

Soil depth- and root diameter-related variations affect root decomposition in temperate pine and oak forests

ABSTRACT Aims Assessment of factors regulating root decomposition is needed to understand carbon and nutrient cycling in forest ecosystems. The objective of this study is to examine the effects of soil depth and root diameter on root decomposition and to analyze the relationship of root decomposition with factors such as soil environmental conditions and initial litter quality. Methods Two decomposition experiments were conducted in natural pine (Pinus densiflora) and oak (Quercus serrata) forests over a 2-year period using the litterbag technique. For the soil depth experiment, 216 litterbags containing fine roots (∅ = 0–2 mm) were buried at 0–10-, 10–20- and 20–30-cm soil depths. Soil properties and soil enzyme activities and microbial biomass at each soil depth were analyzed. For the root diameter experiment, 216 litterbags containing roots 0–1-, 1–2- and 2–3-mm in diameter were buried at 10-cm soil depth. The initial litter qualities (carbon (C), nitrogen (N), calcium (Ca) and phosphorus (P) concentrations) for each of the root diameter classes were analyzed. Litterbags were retrieved after 3, 6, 12 and 24 months in each forest type. Important Findings The root decomposition rate was significantly altered by soil depth and root diameter. After 2 years, the root decay constant at 0–10-cm depth (pine: 0.35 and oak: 0.41) was significantly higher than that at 10–20-cm (0.31 and 0.37) and 20–30-cm (0.32 and 0.33) depths in the P. densiflora and Q. serrata forests. Enzyme activities and microbial biomass declined with soil depth, which may be associated with decreasing soil moisture and organic matter. The decay constant for the 0–1-mm roots (pine: 0.32 and oak: 0.37) was higher than that of 1–2-mm (0.29 and 0.33) and 2–3-mm roots (0.26 and 0.33) for the P. densiflora and Q. serrata forests. Difference in initial P concentration and C/N ratio among the different diameter roots were linearly related with root decomposition. In particular, the increasing C/N ratio with root diameter resulted in decreases in the decomposition rate. These results indicate the surface soil microbial activities and initial C/N ratio of root litter as important drivers of C dynamics in temperate pine and oak forests.

First Report of Pectobacterium carotovorum subsp. brasiliense Causing Blackleg and Stem Rot Disease of Potato in Russia

Blackleg and stem rot of potato (Solanum tuberosum) were observed in several commercial fields in the central part of Russia with up to 40% incidence during 2012 to 2017. Symptoms included decay of internal root and stem tissues, blackening of petiole vascular bundles, and partial yellowing of leaves. The disease can cause serious potato yield losses in the field and storage in Russia. Pectobacterium carotovorum subsp. carotovorum, P. atrosepticum, Dickeya dianthicola, and D. solani are the main causal agents of blackleg disease in Russia (Kornev et al. 2012). Surveys conducted in commercial fields produced multiple samples showing stem rot symptoms. Bacteria were isolated from symptomatic tissues by suspending 1-cm stem sections with lesions in sterile tap water for 10 min, followed by serial dilutions on crystal violet pectate agar (CVP). Bacterial colonies producing pitting on CVP were reisolated and purified on nutrient broth yeast extract medium. Characterization of three isolates provided evidence that a previously unreported blackleg/stem rot pathogen was present in the surveyed region. F126 (from potato ‘Lady Clare’, Samara Region), F128 (from potato ‘Sante’ from Kaluga Region), and F140 (from Moscow region) were gram negative, facultatively anaerobic, and able to grow at 37°C on nutrient agar. They produced typical stem rot symptoms in potato plants inoculated with 10⁷ CFU/ml of the pathogen by stem injection and incubated at 25°C for 48 h. The strains were reisolated successfully from symptomatic potato to complete Koch’s postulates. These strains were negative in polymerase chain reaction (PCR) analyses using specific primers Y45/Y46 for the detection of P. atrosepticum and ADE1/ADE2 for Dickeya (Czajkowski 2011). In contrast, all strains yielded an amplicon (322 bp) in a PCR with primers Br1f and L1r for P. carotovorum subsp. brasiliense (Duarte et al. 2004). 16S rRNA was amplified using universal primer set F27/R1492 (Monciardini et al. 2002). The strains F126, F128, and F140 (GenBank accessions MG570140, MG570141, and MG570142) had 99% sequence identify with 16S rRNA of P. carotovorum subsp. brasiliense type strain BC1 (CP009769.1). Additional loci representing two housekeeping genes were amplified and sequenced: gyrB (MG570137, MG570138, and MG570139) and recA (MG570134, MG570135, MG570136). Primer sets used were as reported by Young and Park (2007) and Dauga (2002). All strains showed 97 to 98% similarity with type strain P. carotovorum subsp. brasiliense BC1. To our knowledge, this is the first report of blackleg and stem rot caused by P. carotovorum subsp. brasiliense on potato in the Russian Federation. According to the data of several diagnostic laboratories, P. carotovorum subsp. brasiliense occurred in >20% potato seed stocks harvested in 2017 and was the predominant blackleg pathogen in fields in the Moscow region in 2018.

THE MAIN FACTORS INFLUENCING EFFICIENCY OF SPRING COMMON WHEAT AGROCENOSIS

The paper presents the results of research (2015– 2018) into the main factors affecting efficiency of agrocenosis of spring common wheat, cultivar Siberian Alliance, with various systems of soil tillage and renewable bio-resources in a grain-fallow rotation. The research was conducted in the northern forest-steppe of Kuznetsk Depression in a threecourse grain-fallow crop rotation (fallow-wheatpeas-barley, barley intercropped with melilot) in a long-term stationary experiment. Various soil tillage systems were applied (deep moldboard, deep combined, minimum combined, minimum moldboard) preceded by bare fallow and green-manured fallow with rape and melilot. The soil of the experimental plot was leached chernozem. Crops of spring common wheat were sown with all types of soil tillage systems by the tillage and sowing machine Tom’5.1. It was revealed that the main factor influencing the yield of spring common wheat is water availability in the planting periods – full tillering, (r = 0.9579), beginning of earring – yellow ripeness, (r = 0.9611; R = 0.9500). A positive effect on wheat productivity was made by cellulosolytic activity and soil structure. The direct correlation between these factors and the crop yield was established, r = 0.6366 – 0.7298 and r = 0.6343 – 0.7103 respectively. A negative effect on the yield of wheat was made by the development of root decay (Bipolaris sorokiniana (Sacc.) Shoem), (r = – 0.4808). It was established that alongside the above-mentioned fac tors, the significant effect on productivity of spring common wheat was made by the systems of soil tillage (72.4%,) and the predecessor (22.0 %). The optimum conditions in agrocenosis of spring common wheat for formation of its yield during the years of research proved to be created by green-manured fallow (with rape) with minimum moldboard and deep moldboard soil tillage (2.72 and 2.78 t/ha respectively), which is 0.55 and 0.51 t/ha higher compared to analogous soil tillage systems preceded by bare fallow – control. Minimum moldboard soil tillage has an economic advantage over others with profitability of 193.6% and production cost at 5,000 rubles per 1 ton of grain.

Using undisturbed soil samples to study how rock fragments and soil macropores affect the hydraulic conductivity of forest stony soils: Some methodological aspects

Forest stony soils have rock fragments and many macropores, the latter arising mainly from the activity of soil fauna and plant root decay. We still lack knowledge about the hydraulic properties of this type of soil, especially when considering the influence of both factors – rock fragments and macropores – on the saturated hydraulic conductivity. This research aims to supplement the method we proposed before to test the hydraulic conductivity of undisturbed soil samples (Ilek and Kucza, 2014; Kucza and Ilek, 2016). We propose to enhance the method by taking into account the impact of rock fragments and macropores on the hydraulic conductivity of forest stony soils, particularly on the hydraulic conductivity of the medium conducting water in the soil, that is, soil matrix. We studied, using artificial samples, how rock fragments influence hydraulic conductivity. To test the enhanced method, we used 33 undisturbed samples taken from the top layers (0–12 cm) of forest stony soils. The results show that rock fragments in the soil can both increase and decrease the infiltration of water by the soil matrix. Rock fragments with diameters close to 20 mm had the least influence on water infiltration. Soil macropores in the samples always increased water infiltration. Empty macropores increased it from two to twenty-four times while filled macropores from three to five times. Our method gives the opportunity to study the hydraulic conductivity of macropores and their physical and chemical properties.

Cacao Root Decay (Caused by Rosellinia Pepo) in Colombia

Root decay is a disease that causes the death of the cacao and shade trees affected and slowly disseminates forming patches of dead trees within the crop. It is caused by Rosellinia spp. but in Colombia the most common specie is Rosellinia pepo. Although cultural control is the recommended practice, however, the results and costs of the work limit its acceptance for the cacao producer. Then, it is necessary to seek other control methods and within them the effect of soil dissinfectans like Formaldhyde and Sodium Hypoclorite and others applied on the soil surface they can be good alternatives.

Zinc Influences Regeneration of Talinum portulacifolium Stem Cuttings in Nutrient Solution

Zinc (Zn) is an essential micronutrient for plant growth and development, but toxic at high concentrations. The present study focused to underline the direct effect of different concentrations (0-50 ppm) of Zn on the regeneration ability and morphological characteristics of Talinum portulacifolium stem cuttings in hydroponic solution over a period of 35 days without the interference of other soil factors. High concentrations of Zn (40-50 ppm) affected callusing, root initiation, root and shoot development to varying levels. At high concentrations, Zn caused stem decay, stunting and browning of roots, wilting, withering and necrotic spots on leaves. Increasing concentrations of Zn inversely affected the lateral shoot development, stem elongation, leaf, root numbers and total root length of the stem cuttings. Though Zn had no significant influence on fresh or dry weights of stem, low concentration (15 ppm) of Zn increased the fresh and dry weights of leaves by 11.17% and 26.79% respectively, compared to 0 ppm and with 77.06-243.80% and 47.92-255.00% compared with those raised in 20-50 ppm. Zn concentrations &gt;10 ppm reduced the root fresh weight by 28.57-90.47% and dry weight by 27.27-90.91% than those at 0 ppm. The Zn content in leaves and stems increased linearly with increasing concentrations of Zn and ranged from 1.09-125.62 ppm and 1.00-110.26 in stems and leaves respectively. The tolerance index varied between 81 and 138 for different concentrations of Zn. The results of the study clearly indicate that high concentrations of Zn inhibit the regeneration of T. portulacifolium stem cuttings.

Chewing function, general health and the dentition of older Australian men: The Concord Health and Ageing in Men Project.

To describe the associations between chewing function with oral health and certain general health characteristics, in a population of community-dwelling older Australian men. Analysis of data obtained from a cross-sectional analysis of the 4th wave of the Concord Health and Ageing in Men Project cohort of 614 participants, 524 whom were dentate, aged 78years and over. Their chewing capacity was assessed using three main indicators: capacity to chew eleven food items ranging from boiled eggs through to fresh carrots and nuts; discomfort when eating; and interruption of meals. Associations with chewing were tested for dentate vs edentate participants, numbers of teeth present, active dental disease and key general health conditions such as disabilities, comorbidities and cognitive status. Log binomial regression models adjusted for age, country of birth, income, education and marital status. Prevalence ratios and 95% confidence intervals were estimated. Twenty-one per cent of participants could not eat hard foods, while 23.1% reported discomfort when eating, and 8.8% reported interrupted meals when eating. There was a threefold difference in the capacity of dentate men to chew firm meat over that of edentulous men (95% CI, 2.0-4.9); a 2.5 times greater likelihood of edentate men reporting discomfort when eating (95% CI: 1.5-4.3); and 1.9 times greater likelihood of edentate participants reporting having meals interrupted (95% CI: 1.4-2.6). Chewing/eating difficulties were associated with both dental status (number of teeth, active dental caries) and self-rated dental health. Fewer than 20 teeth and the presence of active coronal or root decay were associated with more discomfort when eating. General health conditions associated with chewing function included disability, physical activity, comorbidities, cognitive status and depression. Older men's self-rated oral health and general health perceptions were also associated with aspects of chewing function. Poorer self-reported oral health was associated with inability to eat hard foods (95% CI: 1.3-2.7) and with discomfort when eating (95% CI: 2.6-5.1), while poorer self-reported general health was associated with discomfort when eating (95% CI: 1.2-2.2). Falling rates of edentulism may lead to improved chewing and eating function in older men. Maintaining 20 or more natural teeth, and preventing active coronal and root caries should enhance chewing function and promote self-reported health and oral health. Lower capacity to chew hard foods and a higher reporting of discomfort when eating is associated with co-morbidity in older Australian men.

Chitosan as a Potential Postharvest Treatment for Minimizing Rotscausing Decay of some Vegetable Fruits

Fungal pathogens such as Alternaria solani in tomato,Rhizopus stolonifer in strawberry, Botrytis cineara in pepper, Sclerotinia sclerotiorum in cucumber, and Sclerotium rolfsii in carrot causes many losses of postharvest decay of different fruits affect quality and quantity during the storage, marketing and handling. Its control has been and still largely based on the use fungicides. However, it is able to develop resistance to these chemicals very rapidly, so its control has become problematic.Chitosan (poly-β-(1-4)N-acetyl-d-glucosamine),was applied on maycelial growth of fungi and fruits, by dipping fruits in solution 0.05% and 0.2% concentrations for five minutes. Invitro, 0.2% Chitosan was the best concentration for inhibition of mycelial growth of postharvest fungi giving 75.7% inhibition of A. solani, followed by 76.9% of R.stolonfer,then 94.9% of S.rolfsii.While, the 0.05% chitosan gave moderate inhibition of A. solani and R. stolonifer and gave high inhibition on S. rofsii, while the two concentrations achived complete inhibition in B. cinerea and S. sclerotiorum. Chitosan treatments applied with acetic acid on fruits gave significant decrease in disease incidence and disease severity.Resultes indicate that chitosan treatments gives good treatmentfor reducing the maycelial growth of fungi and increasing control of postharvest decay of different fruits and roots.