Influence of temperature on the hatch of Heterodera avenae Woll. populations from Algeria

Nematology ◽  
2001 ◽  
Vol 3 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Aïssa Mokabli ◽  
Jean-Pierre Gauthier ◽  
Roger Rivoal ◽  
Sylvie Valette

AbstractTwo Algerian populations of Heterodera avenae originating from Oued Smar in a sub-humid coastal plain and from Tiaret in an inland semi-arid plain were subjected to different temperature treatments and juvenile emergence evaluated. These populations were compared with two populations, Fr1 and Fr4 from southern and northen France, respectively, which represent two ecotypes with respect to hatching cycles in response to temperature. The two Algerian populations hatched over a wide range of constant temperatures (3 to 25°C) but differed in the times at which juveniles emerged from the cysts. Simulation of seasonal temperature variations (from summer to autumn or winter and, conversely, from winter to spring or summer) demonstrated diapause in these two populations, induced by higher temperature (20 and 25°C) treatments and broken subsequently by lower temperatures (3 and 7°C). Both Algerian populations of H. avenae represent the Mediterranean ecotype, with biological variations that may represent regional adaptations to more or less severe climatic conditions.

2019 ◽  
Vol 70 (9) ◽  
pp. 807
Author(s):  
A. Mobli ◽  
S. Mijani ◽  
A. Ghanbari ◽  
M. Rastgoo

Flax-leaf alyssum (Alyssum linifolium Steph. ex. Willd.) is a winter growing annual weed species widely distributed in many semi-arid cropping regions of Iran, especially in the Khorasan Razavi and East Azerbaijan provinces. The germination of two populations (one each from Khorasan Razavi and East Azerbaijan) of this weed was evaluated under different experimental conditions. Seeds of A. linifolium germinated over a wide range of day/night temperature regimes, with the highest germination percentage observed with a regimen of 20°C/10°C. Light was not required for germination for either population, and >70% seeds germinated under all photoperiods tested. Germination was affected by pH levels; seeds germinated over the pH range 4–9 and germination was maximum at pH 7. For the Khorasan Razavi and East Azerbaijan populations, ≥50% of seeds germinated at a water potential of –0.69 and –0.78 MPa and salinity of 12.64 and 11.7 dS m–1 respectively. Maximum seedling emergence occurred when seeds were slightly covered with soil, but emergence decreased with increasing depth of soil cover, with no emergence at depths >3 cm. These results indicate that A. linifolium germinates in a wide range of climatic conditions and could invade into new regions. Burying the seeds through tillage may reduce their emergence.


Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 927
Author(s):  
Jamshad Hussain ◽  
Tasneem Khaliq ◽  
Muhammad Habib ur Rahman ◽  
Asmat Ullah ◽  
Ishfaq Ahmed ◽  
...  

Rising temperature from climate change is the most threatening factor worldwide for crop production. Sustainable wheat production is a challenge due to climate change and variability, which is ultimately a serious threat to food security in Pakistan. A series of field experiments were conducted during seasons 2013–2014 and 2014–2015 in the semi-arid (Faisalabad) and arid (Layyah) regions of Punjab-Pakistan. Three spring wheat genotypes were evaluated under eleven sowing dates from 16 October to 16 March, with an interval of 14–16 days in the two regions. Data for the model calibration and evaluation were collected from field experiments following the standard procedures and protocols. The grain yield under future climate scenarios was simulated by using a well-calibrated CERES-wheat model included in DSSAT v4.7. Future (2051–2100) and baseline (1980–2015) climatic data were simulated using 29 global circulation models (GCMs) under representative concentration pathway (RCP) 8.5. These GCMs were distributed among five quadrants of climatic conditions (Hot/Wet, Hot/Dry, Cool/Dry, Cool/Wet, and Middle) by a stretched distribution approach based on temperature and rainfall change. A maximum of ten GCMs predicted the chances of Middle climatic conditions during the second half of the century (2051–2100). The average temperature during the wheat season in a semi-arid region and arid region would increase by 3.52 °C and 3.84 °C, respectively, under Middle climatic conditions using the RCP 8.5 scenario during the second half-century. The simulated grain yield was reduced by 23.5% in the semi-arid region and 35.45% in the arid region under Middle climatic conditions (scenario). Mean seasonal temperature (MST) of sowing dates ranged from 16 to 27.3 °C, while the mean temperature from the heading to maturity (MTHM) stage was varying between 12.9 to 30.4 °C. Coefficients of determination (R2) between wheat morphology parameters and temperature were highly significant, with a range of 0.84–0.96. Impacts of temperature on wheat sown on 15 March were found to be as severe as to exterminate the crop before heading. The spikes and spikelets were not formed under a mean seasonal temperature higher than 25.5 °C. In a nutshell, elevated temperature (3–4 °C) till the end-century can reduce grain yield by about 30% in semi-arid and arid regions of Pakistan. These findings are crucial for growers and especially for policymakers to decide on sustainable wheat production for food security in the region.


Forests ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 209
Author(s):  
Luiza Tymińska-Czabańska ◽  
Jarosław Socha ◽  
Marek Maj ◽  
Dominika Cywicka ◽  
Xo Viet Hoang Duong

Site productivity provides critical information for forest management practices and is a fundamental measure in forestry. It is determined using site index (SI) models, which are developed using two primary groups of methods, namely, phytocentric (plant-based) or geocentric (earth-based). Geocentric methods allow for direct site growth modelling, in which the SI is predicted using multiple environmental indicators. However, changes in non-static site factors—particularly nitrogen deposition and rising CO2 concentration—lead to an increase in site productivity, which may be visible as an age trend in the SI. In this study, we developed a geocentric SI model for oak. For the development of the SI model, we used data from 150 sample plots, representing a wide range of local topographic and site conditions. A generalized additive model was used to model site productivity. We found that the oak SI depended predominantly on physicochemical soil properties—mainly nitrogen, carbon, sand, and clay content. Additionally, the oak SI value was found to be slightly shaped by the topography, especially by altitude above sea level, and topographic position. We also detected a significant relationship between the SI and the age of oak stands, indicating the long-term increasing site productivity for oak, most likely caused by nitrogen deposition and changes in climatic conditions. The developed geocentric site productivity model for oak explained 77.2% of the SI variation.


Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 931
Author(s):  
Mona Giraud ◽  
Jannis Groh ◽  
Horst H. Gerke ◽  
Nicolas Brüggemann ◽  
Harry Vereecken ◽  
...  

Grasslands are one of the most common biomes in the world with a wide range of ecosystem services. Nevertheless, quantitative data on the change in nitrogen dynamics in extensively managed temperate grasslands caused by a shift from energy- to water-limited climatic conditions have not yet been reported. In this study, we experimentally studied this shift by translocating undisturbed soil monoliths from an energy-limited site (Rollesbroich) to a water-limited site (Selhausen). The soil monoliths were contained in weighable lysimeters and monitored for their water and nitrogen balance in the period between 2012 and 2018. At the water-limited site (Selhausen), annual plant nitrogen uptake decreased due to water stress compared to the energy-limited site (Rollesbroich), while nitrogen uptake was higher at the beginning of the growing period. Possibly because of this lower plant uptake, the lysimeters at the water-limited site showed an increased inorganic nitrogen concentration in the soil solution, indicating a higher net mineralization rate. The N2O gas emissions and nitrogen leaching remained low at both sites. Our findings suggest that in the short term, fertilizer should consequently be applied early in the growing period to increase nitrogen uptake and decrease nitrogen losses. Moreover, a shift from energy-limited to water-limited conditions will have a limited effect on gaseous nitrogen emissions and nitrate concentrations in the groundwater in the grassland type of this study because higher nitrogen concentrations are (over-) compensated by lower leaching rates.


1977 ◽  
Vol 55 (4) ◽  
pp. 693-703 ◽  
Author(s):  
Gail R. Michener

In 1975 and 1976 the times of spring emergence, breeding, and entry into hibernation were compared for Spermophilus richardsonii and S. columbianus in an area of sympatry in the foothills of the southern Alberta Rocky Mountains. Both species emerged earlier in 1976, which had a warmer than normal spring, than in 1975, which had a cooler than normal spring. In both years S. richardsonii emerged earlier than S. columbianus and remained active longer. Juvenile S. richardsonii entered hibernation when 17–20 weeks old whereas juvenile S. columbianus were 10–11 weeks old. Yearling S. richardsonii bred, whereas yearling S. columbianus did not. Breeding success affected the time of entry into hibernation but not the time of emergence from hibernation in the next spring. A possible relationship between the periodic arousals during hibernation and the emergence pattern of squirrels in spring is discussed. The significance of flexibility of spring emergence, length of the active season, and age at breeding to survival and species ecology is considered.


2014 ◽  
Vol 23 (2) ◽  
pp. 234 ◽  
Author(s):  
Ellis Q. Margolis

Piñon–juniper (PJ) fire regimes are generally characterised as infrequent high-severity. However, PJ ecosystems vary across a large geographic and bio-climatic range and little is known about one of the principal PJ functional types, PJ savannas. It is logical that (1) grass in PJ savannas could support frequent, low-severity fire and (2) exclusion of frequent fire could explain increased tree density in PJ savannas. To assess these hypotheses I used dendroecological methods to reconstruct fire history and forest structure in a PJ-dominated savanna. Evidence of high-severity fire was not observed. From 112 fire-scarred trees I reconstructed 87 fire years (1547–1899). Mean fire interval was 7.8 years for fires recorded at ≥2 sites. Tree establishment was negatively correlated with fire frequency (r=–0.74) and peak PJ establishment was synchronous with dry (unfavourable) conditions and a regime shift (decline) in fire frequency in the late 1800s. The collapse of the grass-fuelled, frequent, surface fire regime in this PJ savanna was likely the primary driver of current high tree density (mean=881treesha–1) that is >600% of the historical estimate. Variability in bio-climatic conditions likely drive variability in fire regimes across the wide range of PJ ecosystems.


2016 ◽  
Vol 48 (3) ◽  
pp. 726-740 ◽  
Author(s):  
Daniele Masseroni ◽  
Alessio Cislaghi ◽  
Stefania Camici ◽  
Christian Massari ◽  
Luca Brocca

Many rainfall–runoff (RR) models are available in the scientific literature. Selecting the best structure and parameterization for a model is not straightforward and depends on a broad number of factors, including climatic conditions, catchment characteristics, temporal/spatial resolution and model objectives. In this study, the RR model ‘Modello Idrologico Semi-Distribuito in continuo’ (MISDc), mainly developed for flood simulation in Mediterranean basins, was tested on the Seveso basin, which is stressed several times a year by flooding events mainly caused by excessive urbanization. The work summarizes a compendium of the MISDc applications over a wide range of catchments in European countries and then it analyses the performances over the Seveso basin. The results show a good fit behaviour during both the calibration and the validation periods with a Nash–Sutcliffe coefficient index larger than 0.9. Moreover, the median volume and peak discharge errors calculated on several flood events were less than 25%. In conclusion, we can be assured that the reliability and computational speed could make the MISDc model suitable for flood estimation in many catchments of different geographical contexts and land use characteristics. Moreover, MISDc will also be useful for future support of real-time decision-making for flood risk management in the Seveso basin.


1913 ◽  
Vol 17 (2) ◽  
pp. 117-131
Author(s):  
Hans Zinsser

The experiments recorded in this paper confirm the observations of Friedberger that acutely toxic bodies can be produced from typhoid bacilli by the action of sensitizer and complement and that, when small quantities of bacteria are used, an excess of sensitization either interferes with the formation of the poisons or leads to a cleavage of the bacterial proteid beyond the poisonous intermediate products spoken of as anaphylatoxins. Unlike the experience of other workers with poisons of this nature, however, our experiments have shown that the action of complement upon typhoid bacilli strongly sensitized or not at all sensitized may be carried on, at body temperature, for considerably longer than twelve hours without leading to a destruction of the poisons, and that this is true when the quantities of the bacteria used vary within the wide range of from one to twelve agar slants. It has been found, in fact, that in the case of this microorganism prolonged exposure at the higher temperature of considerable quantities of bacteria constitutes an unfailing method of regularly obtaining powerful poisons. The results obtained by the use of smaller quantities and the less vigorous complement action at low temperatures are far less regular or satisfactory. It would appear from this that complement action of considerable vigor is required to obtain from this bacillus any appreciable yield of anaphylatoxin, and that the poison, once formed, is not as unstable as that found in other microorganisms by Neufeld and Dold and others. In fact, although we have never observed complete lysis in vitro of the typhoid bacilli treated with antibody and complement, the sensitized bacteria exposed to the action of complement for as long as fifteen hours at 37.5° C. showed, in our experiments, much disintegration, and yet powerful poisons were present. Were the influence of lysis or of the too vigorous action of the serum bodies as rapidly poison-destroying in the case of this bacillus as it has been shown to be in the case of some other bacteria, it would be hard to understand how anaphylatoxins could play any part in the toxemia of typhoid fever. This phase of our experiments, however, seems to indicate that the conditions prevailing in the infected body at the height of this disease would furnish ideal criteria for anaphylatoxin production, since, in such cases, vigorously sensitized bacilli, in large numbers, are under the prolonged influence of considerable quantities of complement, conditions exactly comparable to those prevailing in our experiments. Granted that this state of affairs is actually the case, then the subsidence of the disease might depend merely upon limitation of the supply of antigen, as the increasing bactericidal action of the blood constituents come into play, and upon the consequent diminution of the anaphylatoxin. For as the bacteria diminish and the sensitizer increases, a changed proportion between them is established which, finally, as experiment has shown, results in a failure of anaphylatoxin production. For although our experiments have shown that, within a wide latitude of relative proportions of bacteria and antibody, anaphylatoxin can be formed, beyond this range an excess of one or the other element eventually will prevent their formation. It is not, however, the purpose of this paper to discuss the mechanism of the subsidence of the disease since this phase of the work will necessitate further experimental study. In regard to the experiments with kaolin, we were unable to confirm the contention of Keysser and Wassermann, though it is more than likely that toxic bodies could be formed by the action of complement upon any foreign proteid rendered amenable to its action. We are not inclined to attribute too much importance to these negative results, recording them merely as they occurred. However, should it be found subsequently that anaphylatoxins can be formed in this way, it seems unlikely that they are formed from the sensitizer or amboceptor as matrix, since this was not specifically adsorbed out of concentrated serum by the kaolin in our experiments. On the basis of experiments with so called endotoxins, ,we feel that the existence of such preformed intracellular poisons as an element in typhoid toxemia has not been proved, and is not absolutely necessary for the explanation of the phenomena occurring in this disease. However, the diarrhea, the hemorrhagic lesions, and the protracted symptoms following the injection of extracts and filtrates of the bacillus, differing so strikingly from the acute illness with rapid death or equally rapid recovery resulting from anaphylatoxin poisoning, would justify the assumption that poisons of this nature may still play a part in the disease, adding an additional specific characteristic to the clinical picture. As stated before, however, it is not improbable that all these characteristics may represent merely a more protracted or subacute state of anaphylatoxin toxemia. The experiments with autolysates, although none of them were fatal in their results upon guinea pigs, have sufficiently indicated that poisons comparable to anaphylatoxins can be formed in this way. This would indicate that a reaction of proteolysis, which may take place slowly by autolysis, is hastened by the action of complement, and its velocity is still further augmented by the increase, within certain limits, of the sensitization,—a conception which would attribute to the combined action of complement and sensitizer a function not incomparable to that of the bodies spoken of as catalytic agents.


2018 ◽  
Vol 69 (3) ◽  
pp. 326 ◽  
Author(s):  
Singarayer Florentine ◽  
Sandra Weller ◽  
Alannah King ◽  
Arunthathy Florentine ◽  
Kim Dowling ◽  
...  

Echium plantagineum is a significant pasture weed in the Mediterranean climatic zone of several countries, including Australia. This invasive weed, introduced as an ornamental into Australia (where it is known as Paterson’s curse), quickly became established and is now a significant weed of agriculture. Although E. plantagineum is a well-established, highly competitive weed that thrives under disturbance and is tolerant of a wide variety of conditions, including varying soil moisture and drought, and some aspects of its ecology remain unknown. This study investigated germination response to temperature and light, pH, soil moisture, salinity, and pre-germination exposure of seed to heat and smoke. Temperature was found to be more influential on germination than light and the species is tolerant to a wide range of pH. However, available moisture may limit germination, as may elevated salinity. Management of this weed requires approaches that minimise soil seedbank input or prevent germination of soil seedbanks.


Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Bart M Demaerschalk ◽  
Robert D Brown ◽  
Virginia J Howard ◽  
MeeLee Tom ◽  
Mary E Longbottom ◽  
...  

Introduction: Careful selection and timely activation of clinical sites in multicenter clinical trials is critical for successful enrollment, subject safety, and generalizability of results. Methods: In the Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial (CREST-2), a multidisciplinary Site Selection Committee evaluated applicants referred via participation in CREST, CREST principal investigators (PIs) and other investigators, StrokeNet and industry partners. Data for consideration included performance metrics in CREST and other carotid trials and a site selection questionnaire containing information on the investigators as well as quantitative data on carotid procedures performed. Any FDA warning letters were reviewed. Results: The Committee met bi-weekly for 36 months (n=64 meetings). Applications from 176 sites between March 2014 and July 2016 were evaluated: 153 were approved, 7 are under Committee review, 5 were approved but withdrew, 5 were placed on a waiting list, and 6 were rejected. One-hundred-four sites have completed the regulatory and training requirements to randomize: 51 (49%) academic medical centers, 31 (30%) private hospital-based centers, 16 (15%) private office-based practices, and 6 (6%) Veterans Administration medical centers. The mean times from application-to- approval was 5.2 weeks (interquartile range, 1.9, 6.2), and from approval-to-randomization status was 46.7 weeks (interquartile range, 35.4, 51.7). Specialties of the 104 site PIs are vascular surgery for 35 (33.7%), cardiology for 30 (28.8%), neurology for 25 (24%), neurosurgery for 8 (7.7%), interventional radiology for 4 (3.8%), and interventional neuroradiology for 2 (1.9%). Conclusions: Careful site selection is time-consuming for prospective sites and for trial leadership. Times from application-to-site-approval were modest (mean = 5.2 weeks), in contrast to the times for completing regulatory and training requirements (mean = 46.7 weeks). However, subject enrollment by teams from a wide range of medical centers led by a multi-disciplinary cohort of PIs will promote the generalizability of trial results.


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