bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethics in weed science
Authors: Zimdahl Robert L.
Published: May 2019

Weed science, like most sciences, has distanced itself from social and ethical discourse in theory and practice. This symposium illustrates my point. The 38th meeting of our society is the first time there has been a formal discussion of the ethical aspects of our work. Weed science, we often believe, is value free, as science ought to be. But neither basic nor applied weed science is value free; they are value laden. Operative values include meeting basic human needs through improved food production, promoting the common good through abundant food, improving people's lives through efficient production of safe food, achieving agricultural sustainability, and increasing efficient food and fiber production and farmer profit. Truth pursued via the scientific method is valued and respected, as is belief in the goodness of scientific and technological progress. Most of these values rest on an ethical foundation known as utilitarianism. Most weed scientists and their colleagues in agricultural sciences are utilitarian in that they believe their work should be useful to humans and should promote the greatest good for the greatest number of people. What weed scientists believe and stand for and the validity of the ethical foundation of their utilitarian convictions ought to be central subjects of the weed scientist's research and teaching. Ethical reflection does not necessarily imply criticism or a need for reform, but it does demand intellectual clarity and an ability to affirm who we are, what we do, and what we value. Weed scientists should engage in an exchange about the ideas that are the end result of their experiences and discuss the experiences that give shape, substance, and depth to those ideas. In the absence of internal ethical reflection and value clarification, external distortions—including public criticism—will define the moral universe weed scientists must work in. Without embarrassment, weed scientists have to learn to ask about the ethical foundation of their science.
Interaction of glyphosate with chlorimuron, fomesafen, imazethapyr, and sulfentrazone
Authors: Starke Robert J. , Oliver Lawrence R.
Published: May 2019

Field experiments were conducted on eight weed species to determine if chlorimuron, fomesafen, imazethapyr, or sulfentrazone at two rates (labeled and one-half the labeled rate) were complementary tank mixtures with glyphosate at 210 and 420 g ai ha−1. Laboratory experiments were conducted on barnyardgrass, pitted morningglory, Palmer amaranth, and velvetleaf using radiolabeled glyphosate, chlorimuron, and imazethapyr to determine the absorption and translocation pattern of these herbicides applied alone and in combination. In the field, glyphosate plus chlorimuron tank mixtures were generally additive. Adding chlorimuron did not decrease absorption or translocation of14C-glyphosate by barnyardgrass, pitted morningglory, or velvetleaf. Adding glyphosate increased absorption of14C-chlorimuron by Palmer amaranth and velvetleaf. All four fomesafen plus glyphosate rate combinations were antagonistic to goosegrass, sicklepod, Palmer amaranth, and velvetleaf, and three of the four were antagonistic to barnyardgrass and entireleaf morningglory. Fomesafen decreased absorption and translocation of14C-glyphosate in barnyardgrass, pitted morningglory, and velvetleaf. Ninety percent of glyphosate plus imazethapyr combinations were additive or synergistic, with all rate combinations synergistic for pitted morningglory. Adding glyphosate to imazethapyr increased absorption of14C-imazethapyr by Palmer amaranth and velvetleaf. Glyphosate plus sulfentrazone tank mixtures were antagonistic at all rate combinations for barnyardgrass and Palmer amaranth and at three of the four combinations for goosegrass and entireleaf morningglory, indicating that these herbicides are not complementary in tank mixtures.
Inheritance of diclofop resistance in wild oat (Avena fatuaL.) biotypes from the Willamette Valley of Oregon
Authors: Seefeldt Steven S. , Hoffman David L. , Gealy David R. , Fuerst E. Patrick
Published: May 2019

Inheritance of resistance to diclofop was studied in three wild oat biotypes (designated B, C., and H) from the Willamette Valley of Oregon. Cultivated oat (cultivar ‘Monida’) was crossed, including reciprocals, to three wild oat biotypes. Leaves of each F1plant were spotted with diclofop as a nondestructive test for resistance or susceptibility. All F1hybrids were resistant, indicating that resistance is dominant and is under nuclear control. The F2plants where Monida was the maternal parent were screened with diclofop, and F2plants of the Monida/C cross were screened with fenoxaprop because the parent C biotype was resistant to fenoxaprop. At lower doses, a 3:1 (R:S) segregation ratio in F2was observed and at higher doses a 1:3 (R:S) segregation ratio was often observed. The F2:3families segregated in a 1:2:1 (all resistant : segregating resistant and susceptible all susceptible) ratio when treated with a 1.1-kg ae ha−1dose of diclofop. This confirms that resistance to diclofop in the B, C, and H biotypes is primarily under monogenic control, with resistance being dominant to susceptibility at lower herbicide doses. At increased doses, susceptibility becomes dominant. Knowledge of the inheritance of resistance may help in the development of containment measures to prevent the spread of herbicide-resistance genes.
Effect of proximity factors on competition between winter wheat (Triticum aestivum) and Italian ryegrass (Lolium multiflorum)
Authors: Hashem Abul , Radosevich S. R. , Roush M. L.
Published: May 2019

Density and spatial arrangement (rectangularity) effects on the competitive relationships, yield performance, and dynamics in canopy dominance of winter wheat and Italian ryegrass were evaluated using two addition series experiments. In experiment 1, combinations of six densities of each species formed the treatment matrix of addition series. In experiment 2, each species was tested at four densities and three rectangularities (RE) of winter wheat. In monocultures, crop density (plants per square meter) explained 82 to 85% of the total variation in the per-plant biomass of winter wheat in experiment 1. In mixtures of crop and weed, initial wheat density (N1) and initial ryegrass density (N2) and interaction of N1and N2explained 74 to 80% of the total variation in the per-plant biomass of winter wheat and 68 to 79% of Italian ryegrass in experiment 1. Intraspecific competition was apparent between 15 and 90 days after emergence (DAE) in winter wheat and between 90 and 170 DAE in Italian ryegrass. In mixtures, RE influenced plant size of Italian ryegrass up to 50 DAE only. Maximum winter wheat intraspecific competition occurred at 170 DAE, but maximum interspecific competition occurred during reproductive stages in mixtures. High RE increased seed yield, seed size, and harvest index of winter wheat and reduced biomass of Italian ryegrass. Grain yield of winter wheat was reduced up to 92% by competition from ryegrass. Even nine ryegrass plants in 100 winter wheat plants m−2reduced winter wheat grain yield by 33%. However, the extent of loss in winter wheat grain yield was less in RE 16 (wider spacing) than in RE 1 (square planting) or 4 (close row spacing). Winter wheat was the stronger competitor during vegetative stages, but Italian ryegrass became the stronger competitor during the reproductive stages of development. Winter wheat leaves dominated at the top canopy during the vegetative stage, but ryegrass dominated at the top canopy during the reproductive stages. In the top canopy of mixtures at 200 DAE, the leaf area indices (LAI) of ryegrass was 6.6 times greater than winter wheat at RE 1 compared to only 1.6 times at RE 16. Greater LAI of Italian ryegrass in the top canopy reduced photosynthetically active radiation available to winter wheat by 68% at booting stage.
Nitrogen interactions with medusahead (Taeniatherum caput-medusaessp.asperum) seedbanks
Authors: Young James A. , Trent James D. , Blank Robert R. , Palmquist Debra E.
Published: May 2019

Medusahead is an invasive annual grass that, once established, severely affects range-land productivity and stability. Medusahead builds large seedbanks in the litter and on the soil surface. Effective weed control of medusahead involves either inhibiting germination from the seedbank, eliminating the seedbank, or enhancing germination so that plants are available for control. The purpose of this study was to determine the influence of nitrogen enrichment, immobilization, and nitrification inhibition treatments in the field on the size and germination status of medusahead seedbanks. The germination status of medusahead seeds in seedbanks was determined by periodically collecting field samples of surface soil and litter and bioassaying them in greenhouse emergence tests. Control seedbanks had increased seedling emergence with KNO3or GA3enrichment of the bioassay substrate. The combination of these two materials increased emergence. Nitrogen enrichment increased seedling establishment in the field. Carbon enrichment in the field decreased seedling establishment and increased medusahead seeds in seedbanks. Nitrapyrin treatment decreased medusahead in the field similar to carbon enrichment. In comparison to the control or other treatments, GA3enrichment was not as effective in increasing emergence from nitrapyrin-treated bioassay samples. The combination of carbon and nitrapyrin treatments was very effective in eliminating medusahead emergence in the field, but in wetter years, it never completely eliminated medusahead seedling recruitment and subsequent reproduction. These treatments have promise for influencing succession in medusahead infestations if an adapted perennial species, capable of competing under low nitrogen levels, becomes available.
Monitoring the spread of ACCase inhibitor resistance among wild oat (Avena fatua) patches using AFLP analysis
Authors: Andrews Todd S. , Morrison Ian N. , Penner Greg A.
Published: May 2019

The relative genetic similarity of 37 wild oat samples was determined using amplified fragment length polymorphism (AFLP) analysis. These data were compared with the herbicide-resistance characteristics of each sample to determine the importance of mutation and gene flow in the spread of Acetyl-CoA Carboxylase (ACCase) inhibitor resistance. There was a strong association between the genotypic clustering of samples, their herbicide-resistance characteristics, and their field of origin. Up to eight separate patches in a field were genetically similar, confirming that gene flow by seed movement is important in the distribution of resistant (R) wild oat seed. A greater emphasis on field scouting and treatment of wild oat patches could reduce the spread of resistance within fields. Samples collected from different fields were also found to be genetically similar, indicating that R wild oat was spread between fields. Improved sanitation of tillage and harvesting equipment and the use of certified seed could limit such seed movement.
Differential response of palmleaf morningglory (Ipomoea wrightii) and pitted morningglory (Ipomoea lacunosa) to flooding
Authors: Gealy David
Published: May 2019

Palmleaf morningglory (IPOWR) and pitted morningglory (IPOLA) were compared in field and greenhouse tests under simulated rice field conditions to quantify flood tolerance characteristics of the two species. IPOWR survived a 13-cm flood in the field if the flood was applied 12 days after planting (DAP) or later. In contrast, IPOLA did not survive floods applied before 19 DAP. Only IPOWR survived a 5-cm flood applied 5 DAP in the field. In the greenhouse, both species were unable to emerge from under 1 cm of soil when flooded greater than 1 cm deep. Although both species emerged from water-saturated soil, IPOWR emerged earlier and produced more dry weight than did IPOLA. Emergence from the water surface of 2-cm-tall IPOWR was better than that of IPOLA when submerged in water up to 7 cm deep, and total dry weight (as a percent of a nonflooded control) was two to four times greater for IPOWR. Even a 5-cm flood reduced leaf area, height, dry weight, and photosynthesis of IPOLA more than that of IPOWR. At 20 C and low oxygen (1%), germination percentage of IPOWR was about four times higher than IPOLA. Germination, growth, and certain physiological processes of IPOWR are more tolerant than those of IPOLA to moderately deep floods (and low soil oxygen levels). Thus, IPOWR is potentially a greater weed problem than IPOLA in rice fields. The fact that neither species was capable of emerging from soil under even shallow flood depths helps explain why morningglories are prevalent only in shallow or water-saturated areas on rice field levees.
Effect of imazamox, fomesafen, and acifluorfen soil residue on rotational crops
Authors: Cobucci Tarcísio , Prates Hélio T. , Falcão Christian L. M. , Rezende Marcio M. V.
Published: May 2019

Field studies were conducted at Goiânia, GO, Brazil, on an Oxisol (clayey, kaolinitic, isothermic, Typic Haplustox) and at Jussara, GO, Brazil, on an Oxisol (loamy sand, kaolinitic, isothermic, Typic Haplustox) during 1995 and 1996 to determine the carryover effect of fomesafen, imazamox, and acifluorfen, applied to edible bean, on rotational crops (maize, sorghum, rice, and millet) and to estimate the level of soil residues under Brazilian Savanna conditions. Averaged across locale, year, and rate, fomesafen dissipation time (DT50) (37.5 d) was longer than acifluorfen (27.5 d) and imazamox (25.9 d). For both locations, soil herbicide persistence (average of herbicides) was longer in 1995 than in 1996. This was due to higher soil moisture content in 1996. The sensitivity of rotational crops to fomesafen and imazamox residues was, in decreasing order: sorghum, corn, millet, and rice, and for acifluorfen: sorghum, corn, rice, and millet. The period between herbicide application and rotational crop planting (PAP) varied in agreement with the sensitivity of rotational crops to herbicide residues in soil and the persistence of the herbicide. Considering both location and year, the PAP for fomesafen (250 g ai ha−1) ranged from 69 to 132 d for corn, 114 to 179 d for sorghum, 29 to 95 d for rice, and 52 to 111 d for millet; the PAP for imazamox (40 g ai ha−1) ranged from 68 to 111 d for corn, 78 to 139 d for sorghum, 25 to 75 d for rice, and 40 to 102 d for millet; and the PAP for acifluorfen (170 g ai ha−1) ranged from 56 to 89 d for corn, 96 to 139 d for sorghum, 61 to 95 d for rice, and 43 to 82 d for millet.
Chlorophyll fluorescence evaluation of agrochemical interactions with propanil on propanil-resistant barnyardgrass (Echinochloa crus-galli)
Authors: Norsworthy Jason K. , Talbert Ronald E. , Hoagland Robert E.
Published: May 2019

Resistance to propanil by a barnyardgrass (BYG) biotype has been reported, and its occurrence is becoming widespread in U.S. rice-producing regions. Interactions between propanil and the herbicides anilofos, molinate, pendimethalin, piperophos, quinclorac, and thiobencarb and the insecticide carbaryl were evaluated in laboratory studies for improved control of propanil-resistant barnyardgrass (R-BYG). Chlorophyll fluorescence measurements of BYG leaf segments were used to ascertain electron transport inhibition and to assess the synergy/antagonism of propanil (100 μM) with the various additives (50 μM). Synergistic effects on photosynthetic inhibition were found with anilofos, carbaryl, pendimethalin, and piperophos in combination with propanil. Such synergistic actions of chemicals with propanil may lead to chemical combinations useful for R-BYG control.
Field horsetail (Equisetum arvense)—effects of potassium under different light and nitrogen conditions
Authors: Andersson Torsten N. , Lundegårdh Bengt
Published: May 2019

Field horsetail shoots were severed from the rhizomes and grown hydroponically with and without shade (40 and 190 μmol m–2s–1photosynthetic photon flux) under six different nutrient regimes, by using nutrient solutions with different amounts of nitrogen (N) and potassium (K) (6/42 mmol L–1N; 7/15/24 mmol L–1K). Nutrients were supplied daily with the same volumes for the six different nutrient solutions at exponentially increasing rates corresponding to a maximum relative growth rate (RGR) of 12.5% from days 0 to 31 and 6% from days 32 to 48. RGR was calculated for the highest N and K rate. Photosynthetic rate and stomatal conductance to water vapor were determined on day 48, then the plants were harvested. The fresh weight (FW) and dry weight (DW) of different plant components were determined. Shade completely inhibited growth of tubers and fertile shoots and drastically reduced RGR, average aerial shoot height, and DW of shoots and rhizomes. N supplied at the high rate to unshaded plants increased the growth of all parts or the plant except fertile shoots and tubers. No effects of K were detected at the low N rate, whereas at the high N rate, K significantly increased total DW and belowsurface DW. RGR never exceeded 10% d–1. In the unshaded treatments, the K concentration was higher in aerial shoots, 150 to 240 μmol g–1FW, than in belowsurface organs, 30 to 90 μmol g–1FW. Shoot growth was significantly reduced at shoot K concentrations below 150 to 210 μmol g–1FW, and root growth was significantly reduced at root K concentrations below 30 to 50 μmol g–1FW. K significantly increased maximum net photosynthetic rate, 10 μmol CO2m–2s–1, at light saturation, 1,300 μmol m–2s–1, in unshaded plants, whereas it reduced the light compensation point and respiratory losses of CO2in darkness. It is concluded that field horsetail is a typical sunny habitat species with a rather high K demand.
Characterizing traits that enhance the competitiveness of winter wheat (Triticum aestivum) against jointed goatgrass (Aegilops cylindrica)
Authors: Ogg Alex G. , Seefeldt Steven S.
Published: May 2019

Our objective was to identify traits in winter wheat important to competitiveness against jointed goatgrass, measured as increased wheat yields and reduced jointed goatgrass seed production. Jointed goatgrass is an important winter annual grass weed that cannot be controlled selectively in winter wheat. Seven cultivars of soft white winter wheat were grown with and without competition from jointed goatgrass over two growing seasons. Measurements of numerous traits of winter wheat and jointed goatgrass were recorded throughout each growing season. The data were analyzed using path analysis with latent variables to determine which traits most enhanced competitiveness. In a drier year, increased rate of height development was important in maintaining wheat yields when wheat was growing in competition with jointed goatgrass. Increased rate of height development also was an important trait in reducing jointed goatgrass seed production. In a wet year compared to a dry year, the number of wheat heads per plant, the rate of water use, and weight gain were positively correlated to maintaining winter wheat yields. Jointed goatgrass seed production in the wet year was reduced overall compared to the dry year, but from the cultivars tested, there were no traits identified that were critical in enhancing this loss of seed production. This study suggests that cultivars with greater height development rates will be more competitive when growing in fields infested with jointed goatgrass.
Competition and control of weeds in soybean
Authors: Chhokar Rajender Singh , Balyan Rajender Singh
Published: May 2019

Two field experiments were carried out from 1993 to 1995 to evaluate the critical period of weed control and to develop suitable weed management practices for jungle rice, horse purslane, and cockscomb in soybean. Horse purslane was more competitive during early growth stages (up to 45 days after sowing [DAS]) and cockscomb was more competitive during later growth stages, whereas jungle rice was competitive throughout the growing season. The critical period of weed control was found to be 30 to 45 DAS. Weed-free maintenance up to 45 DAS resulted in a 74% increase in grain yield of soybean over the unweeded control. Keeping soybean weed free for 45 d or allowing weeds to remain in the crop for less than 30 d resulted in no significant yield loss. Sequential application of a reduced rate of soil-applied trifluralin 1.0 kg ha–1(0.67 ×) with postemergence fluazifop 0.75 kg ha–1(0.75 ×) or a reduced rate of soil-applied trifluralin or pendimethalin at 1.0 kg ha–1(0.67 ×) followed by hand hoeing 35 DAS provided better control of a broad spectrum of weeds than a single application of a postemergence herbicide applied at reduced or recommended rates. Integration of reduced rates of soil-applied herbicides with post-emergence herbicides or hand hoeing 35 DAS produced soybean yields similar to the hand-weeded treatment. Compared to the weed-free or integrated weed control, a single application of soil-applied or postemergence herbicide did not control a broad spectrum of weeds and reduced soybean yield.
Relative influence of crop rotation, tillage, and weed management on weed associations in spring barley cropping systems
Authors: Légère Anne , Samson Nathalie
Published: May 2019

Generalizations concerning the effects of management practices on weed community dynamics often lack robustness, most likely because of the concomitant effects of agronomic and environmental factors. However, such generalizations, when valid, provide useful grounds for predictions and are thus desirable. This study attempted to evaluate the relative importance of crop rotation, tillage, and weed management as factors affecting weed communities and tested the hypothesis of an association between management practices and weeds from certain life cycle groups. Principal component analysis (PCA) of weed density data from a 4-yr field study conducted on a Kamouraska clay and a Saint-André gravelly sandy loam at La Pocatière QC, Canada, identified groups of weed species, while an analysis of variance (ANOVA) of PCA scores associated these groups with management factors. A multivariate analysis of variance (MANOVA) of regression coefficients describing time courses of density for each species confirmed treatment effects. Species segregated roughly according to life cycles. Interactions among weed management intensity, tillage, and crop rotation mostly explained species dominance in the various cropping systems. A first group of species, mostly annual dicots, largely dominated in minimum weed management treatments; their relative importance in each rotation varied with their level of susceptibility to postemergence herbicides. A second group included annuals and perennials, whose commonality seemed to be their tolerance to herbicides; these species also had a particular affinity for chisel and no-till treatments. A third group was formed by perennial species, each with a different response to tillage. The tenuous correspondence between commonly used classification schemes and management factors suggests that other aspects of weed biology (e.g., seed size, dispersal, production, germination requirements, and seedbank longevity) should be considered when trying to explain and predict the presence and dominance of certain weed species with regard to management practices.
Influence of bromoxynil on annual grass control by graminicides
Authors: Culpepper A. Stanley , York Alan C. , Brownie Cavell
Published: May 2019

Greenhouse experiments were conducted to determine the effect of mixing bromoxynil with clethodim, sethoxydim, fluazifop-P, fluazifop-P plus fenoxaprop-P, or quizalofop-P on annual grass control. Antagonism with mixtures of bromoxynil and graminicides was dependent upon species and the graminicide in the mixture. Goosegrass control was unaffected by mixing bromoxynil with any graminicide. Mixing bromoxynil with clethodim, sethoxydim, fluazifop-P, or fluazifop-P plus fenoxaprop-P had no effect on control of Texas panicum, but the rate of quizalofop-P required for 80% control was increased 240%. Mixing bromoxynil with clethodim or sethoxydim had no effect on control of large crabgrass or yellow foxtail, but the rate of fluazifop-P, fluazifop-P plus fenoxaprop-P, or quizalofop-P required for 80% control was increased 180 to 290%. Antagonism of large crabgrass and yellow foxtail control with mixtures of quizalofop-P and bromoxynil increased as the rate of bromoxynil increased. Antagonism toward large crabgrass and yellow foxtail was alleviated by applying bromoxynil 6 d before the graminicides or 3 or 6 d after the graminicides.
Effect of environmental conditions on the dormancy and germination of volunteer oilseed rape seed (Brassica napus)
Authors: López-Granados Francisca , Lutman Peter J. W.
Published: May 2019

The conditions causing the onset of secondary dormancy in seed of winter oilseed rape cultivars Falcon and Libravo were investigated in a series of laboratory experiments to provide practical guidance on how to minimize the persistence of volunteer oilseed rape seed. The germination of recently harvested oilseed rape seed in moist conditions at 12 C was close to 100% in both darkness and under white light. Imbibition in water stress with an osmotic potential (ψ) of −1,500 kPa at 12 C in far-red light (FR) or dark for more than 5 d induced secondary dormancy in both cultivars. Treatment with FR was more effective than darkness at inducing secondary dormancy. Libravo produced more dormant seed than Falcon. Imbibition in FR and absence of water stress (ψ = 0 kPa) decreased germinability especially at the low temperature (6 C). These conditions resulted in 19.4 and 27.2% dormant seed for Libravo and Falcon, respectively. The results suggest that phytochrome is involved in the induction of secondary dormancy in oilseed rape. In practice, much oilseed rape seed is buried by postharvest cultivation in late summer (low hydric conditions) and exposed to water stress and darkness for some time. To avoid soil seed persistence and subsequent volunteer oilseed rape, seed must be retained at the soil surface when there is adequate moisture available. Therefore, incorporation of seed by tillage should be avoided or delayed as long as possible.
Effect of tillage and interference on common cocklebur (Xanthium strumarium) and sicklepod (Senna obtusifolia) population, seed production, and seedbank
Authors: Bararpour Mohammad T. , Oliver Lawrence R.
Published: May 2019

Common cocklebur and sicklepod are troublesome weeds in soybean in the southern United States. A field experiment was conducted from 1991 through 1995 to determine (1) the influence of tillage (no-till and tilled after initial seed deposition) and intraspecific and interspecific interference on seed production potential, emergence pattern, and soil seedbank of common cocklebur and sicklepod, and (2) the dominant species after introduction into a weed-free field. Under intraspecific interference, 1,430 and 1,392 common cocklebur achenes m−2and 1,827 and 5,435 sicklepod seed m−2were deposited to the seedbank after 1 and 2 yr of seed production, respectively. For both species, approximately 11% of the initial seedbank emerged under tilled conditions the first year after deposition. Under no-till conditions, only 0.7% of common cocklebur and 1.6% of sicklepod emerged. The second year after deposition, common cocklebur emergence in no-till decreased to 0.25% of the initial seedbank, while sicklepod increased to 8% of the initial seedbank and remained higher than in tilled plots. Under tilled conditions, common cocklebur became the dominant species, and sicklepod became dominant under no-till conditions. Seedbank depletion was greater for both species under tillage. Three years after initial seed deposition, sicklepod seed was 100% viable but common cocklebur achenes were not viable. Under no-till conditions, common cocklebur was depleted in the seedbank but sicklepod was not. Thus, sicklepod poses a greater long-term weed problem than common cocklebur, especially under no-till conditions.
Allelopathic activity of Mexican sunflower (Tithonia diversifolia) in soil
Authors: Tongma Suthep , Kobayashi Katsuichiro , Usui Kenji
Published: May 2019

Laboratory experiments were undertaken to investigate the allelopathic activity of Mexican sunflower in soil as well as to determine the effect of several soil factors on activity. There was a decrease in shoot and root growth of the test plant species when grown in soil previously planted with Mexican sunflower. However, seed germination was not affected. Soil-water separated from the same soil also inhibited shoot and root growth. A water extract from Mexican sunflower leaves applied to soil also reduced shoot and root growth, but the degree of inhibition varied among test plant species. Incorporation of dry Mexican sunflower leaves into soil at the rate of 1 and 2% (w/w) inhibited the growth of rice seedlings. The phytotoxic activity of incorporated leaf residue diminished 4 wk after treatment of soil. The inhibitory effect of a leaf water extract in nonautoclaved soil was less than in autoclaved soil and the phytotoxic effect to rice seedling grown in autoclaved soil was less than in autoclaved sand. It is suggested that the decrease in allelopathic activity of Mexican sunflower extract and its residue in soil is due to the action of soil microorganisms and the soil adsorption of the active components.
Above- and belowground interference of wheat (Triticum aestivum) by Italian ryegrass (Lolium multiflorum)
Authors: Stone Martin J. , Cralle Harry T. , Chandler James M. , Miller Travis D. , Bovey Rodney W. , Carson Katherine H.
Published: May 2019

Greenhouse experiments in central Texas assessed the relative importance of above- and belowground interactions of semidwarf Mit wheat and Marshall ryegrass during vegetative growth. One experiment used partitions to compare the effect of no (controls), aboveground only, belowground only, and full interaction for 75 d after planting (DAP) one wheat and nine ryegrass plants in soil volumes of 90, 950, and 3,800 ml. The results with the different soil volumes were similar. Wheat growth in the aboveground interaction only did not differ from controls. However, the full or belowground only interaction of wheat with ryegrass reduced wheat height, leaf number, tillering, leaf area, percent total nonstructural carbohydrates in shoot, and dry weights of leaves, stems, and roots 45 and 75 DAP compared to controls. Wheat in full and belowground interaction only did not differ from one another in growth. A replacement series experiment of 56 d also showed that the competitive advantage of ryegrass was relatively greater in root than in shoot growth. No allelopathic response of wheat to ryegrass occurred. While the tallness of the semidwarf wheat minimized aboveground interference by ryegrass, the root growth of the thinner and more fibrous roots of ryegrass greatly enhanced its belowground competitiveness.
Influence of corn (Zea mays) population and row spacing on corn and velvetleaf (Abutilon theophrasti) yield
Authors: Teasdale John R.
Published: May 2019

Research was conducted to determine the optimum population and row spacing for corn production and for suppressing velvetleaf growth and seed production. Corn was grown in a factorial arrangement of three populations targeted at 64,000 (1 ×), 96,000 (1.5 ×), or 128,000 (2 ×) plants ha−1and two row spacings of 38 or 76 cm. Influences on corn were determined in weed-free plots, and influences on velvetleaf were determined for target plants established at 1.5–m intervals along the center of corn interrows. Four velvetleaf plantings were made at weekly intervals beginning at corn planting. Corn row spacing had little influence on corn or velvetleaf. Corn yield exhibited a parabolic response to population with a maximum of approximately 90,000 plants ha−1in one year, no response to population in another year, and a linear decline with increasing population in a dry year. Velvetleaf seed production was reduced 69 to 94% by the 1.5 × population and 99% by the 2 × population compared to the standard 1 × population when velvetleaf emerged with corn. Velvetleaf seed production was eliminated when velvetleaf emerged at or later than corn leaf stages 3, 5, and 6 for corn populations of 2 ×, 1.5 ×, and 1 ×, respectively. Reduced velvetleaf seed production was correlated with lower positioning of plants in the corn canopy and reduced light availability. Results suggest that higher corn populations could aid integrated weed management strategies by reducing seed production and limiting the build-up of weed populations.
Metolachlor and metribuzin losses in runoff as affected by width of vegetative filter strips
Authors: Tingle Christopher H. , Shaw David R. , Boyette Michele , Murphy Glen P.
Published: May 2019

Tall fescue vegetative filter strips 0.5 to 4.0 m wide were evaluated for their ability to reduce losses of metolachlor, metribuzin, and runoff (water and sediment) in conventionally tilled soybean. Differences in the parameters studied were significant between filter and no filter strips, regardless of filter strip width. Two days after treatment, metribuzin concentration in runoff from the unfiltered treatment was 231 ng ml−1; filter strips reduced this amount to 119 ng ml−1or less. Similar trends were observed with metolachlor, with concentrations of 1,009 ng ml−1from the unfiltered, whereas filter strips of any width reduced this to 523 ng ml−1or less. Metribuzin loss during the growing season was 41 g ai ha−1, or 9.8% of the amount applied when no filter strip was present. The addition of a filter strip, regardless of width, reduced cumulative metribuzin losses to 11 g ha−1or less. Similar results were noted with metolachlor. Filter strips, regardless of width, reduced cumulative runoff and sediment loss at least 46 and 83%, respectively.
Photothermal time describes common ragweed (Ambrosia artemisiifoliaL.) phenological development and growth
Authors: Deen William , Hunt L. Anthony , Swanton Clarence J.
Published: May 2019

The ability to predict weed phenological development under field conditions is fundamental to the development of mechanistic weed–crop competition models. We studied how phenological development of common ragweed grown under field conditions could be explained using temperature and photoperiod responses derived from growth room experiments. We also determined the relationship between phenological development and common ragweed leaf area, dry matter production, and partitioning. Phenological development of common ragweed emerging at different times in the field was described by photothermal time based on temperature and photoperiod responses derived from growth room experiments. Estimated dates of phenological events of common ragweed were within 4 d of recorded values. Common ragweed seedling density did not influence phenological development. Common ragweed leaf area development, biomass partitioning, and total biomass were related to photothermal time accumulation. The results of this study are consistent with our hypothesis that phenological development is a major factor influencing the outcome of weed–crop competition. Results obtained from this study can be incorporated into a mechanistic model of weed–crop competition.
Rainfall influence on imazethapyr bioactivity in New Jersey soils
Authors: Ayeni Albert O. , Majek Bradley A. , Hammerstedt Jeff
Published: May 2019

Greenhouse studies were conducted with soil columns to determine the influence of rainfall amount, intensity, and time of application on the bioactivity of 0.07 kg ae ha−1imazethapyr in three soils of New Jersey: the Berryland sand (BLS) (sandy, siliceous, mesic Typic Haplaquod), Aura sandy loam (ASL) (mixed, mesic Typic Hapludult), and Quakertown silt loam (QSIL) (mixed, mesic Typic Hapludult). The Brockman-Duke simulated rainfall machine was used for rainfall application and smooth pigweed as an imazethapyr bioactivity indicator. As rainfall amount increased from low to high (75 to 300 mm mo−1equivalent) imazethapyr bioactivity declined significantly in BLS and ASL but was unaffected in QSIL. Rainfall intensity from 6 to 25 mm h−1had no effect on imazethapyr bioactivity in the three soils. A delay in rainfall application up to 14 d after herbicide application significantly reduced the bioactivity of imazethapyr in BLS but had no effect in ASL and QSIL.
Evolved resistance to glyphosate in rigid ryegrass (Lolium rigidum) in Australia
Authors: Powles Stephen B. , Lorraine-Colwill Debrah F. , Dellow James J. , Preston Christopher
Published: May 2019

Following 15 yr of successful use, glyphosate failed to control a population of the widespread grass weed rigid ryegrass in Australia. This population proved to be resistant to glyphosate in pot dose-response experiments conducted outdoors, exhibiting 7- to 11-fold resistance when compared to a susceptible population. Some cross-resistance to diclofop-methyl (about 2.5-fold) was also observed. Similar levels of control of the resistant and susceptible populations were obtained following application of amitrole, chlorsulfuron, fluazifop-P-butyl, paraquat, sethoxydim, sirnazine, or tralkoxydim. The presence of glyphosate resistance in a major weed species indicates a need for changes in glyphosate use patterns.
Imazethapyr bioactivity and movement in soil
Authors: Jourdan Scott W. , Majek Bradley A. , Ayeni Albert O.
Published: May 2019

A bioassay using red beet root length indicated an increase in imazethapyr bioactivity in Berryland sand (BLS) as soil pH increased from 3.7 to 6.5. Increasing pH above 6.5 had no effect on imazethapyr bioactivity. The lowest imazethapyr concentrations detected by the bioassay at pH 6.5 were 0.5, 1, 2.5, and 5 to 10 μg kg−1in acidwashed quartz sand, BLS, Aura loamy sand, and muck soil, respectively. After application of 0.07 kg ae ha−1with 12.5 mm of simulated rainfall at 3-d intervals, imazethapyr remained in the 0 to 15 cm soil in BLS soil columns. Under this rainfall regime, the herbicide moved 30 cm deep 5 mo after application, but residues decreased significantly in surface soil. Imazethapyr bioactivity was highest and mobility was lowest at low soil temperature (10 C) and low moisture (4 to 6% w/w). Imazethapyr movement was monitored successfully using the red beet root length bioassay, and an herbicide residue map was developed to show the pattern of imazethapyr bioactivity in soil columns.
El CICR, mediador humanitario en el conflicto colombiano Posibilidades y límites
Authors: Jenatsch Thomas
Published: May 2019

Los cinco helicópteros rusos de transporte levantaban mucho polvo cuando, el 15 de junio de 1997, depositaban en Cartagena de Chairá su valiosa carga: 70 soldados de las fuerzas armadas gubernamentales, apresados por la guerrilla tras haber perdido un combate, nueve meses y medio antes. Con el espectacular aterrizaje en la selva comenzaba su libertad y finalizaba, asimismo, un trágico episodio de guerra, que había humillado a los altos mandos militares y había tenido a todo el país en ascuas. Tanto mayor fue la alegría cuando los 70 soldados, dados por desaparecidos, pudieron finalmente abrazar a la respectiva madre y toda Colombia pudo abrigar, durante algunos instantes, le dulce ilusión de una paz cercana. En presencia de observadores internacionales y de incontables periodistas, los jefes de la guerrilla concluyeron con un patético festejo la entrega de los soldados al CICR. Luego, éstos volvieron a subir a los helicópteros.
The aspartic proteinase is expressed inArabidopsis thalianaseeds and localized in the protein bodies
Authors: Mutlu Asuman , Chen Xia , M. Reddy Sridhar , Gal Susannah
Published: May 2019

We have been studying a seed aspartic proteinase, termed AtAP, fromArabidopsis thaliana.In previous work, we purified the proteinase, analysed its activity and isolated the cDNA sequence. In this paper, the expression of the mRNA for the aspartic proteinase was analysed in seed tissues both by Northern blots for overall regulation and byin situhybridization to follow cell-specific localization of message. We found a 1.9 kb aspartic proteinase message in dry seeds and seed pods. This message was expressed in many different cell types of the mature dry seed. The localization of the protein within these cells was also determined. Antibodies were raised against the AtAP and purified using affinity chromatography on an AtAP–immobilized-pepstatin A–agarose column. This purified antibody recognized several AtAP peptides in seeds. To localize the enzyme in cells, we isolated protein bodies from the dry seeds of Arabidopsis using a non-aqueous isolation method. The AtAP activity and antigenic peptides were found to be highest in the protein body fraction and co-localized with the seed storage protein 2S albumin and the vacuolar marker enzyme α-mannosidase. This protein body localization of the AtAP was confirmed with immunocytochemical localization by electron microscopy and shows that the protein is not secreted by these cells.
Internal anatomy of individual tomato seeds: relationship to abscisic acid and germination physiology
Authors: Downie Bruce , Gurusinghe Sunitha , Bradford Kent J.
Published: May 2019

Tomato seeds that have been dried, imbibed and redried (primed) develop internal free space between the embryo and endosperm. Seeds of the ABA-deficient sitiens(sitw) tomato mutant can exhibit internal free space at the completion of seed development even without priming. Both primed and sitwseeds germinate more rapidly than untreated wild-type seeds. To determine whether internal anatomy predicts germination physiology, individual sitwand primed wild-type seeds were sorted into three categories based upon the extent of internal free space observed non-destructively using X-radiography. Category 3 (C3, extensive free space present) sitw seeds completed germination more rapidly than all other seed categories and genotypes in water, in abscisic acid (ABA) or under far-red illumination. The force necessary to puncture the endosperm caps (and testa) of C3 sitw seeds was less, and the percentage of nuclei in C3 sitw radicle tips in the G2 stage of the cell cycle was greater than for all other seed categories. Wild-type seeds exhibited free space following long-term priming, but germination was still prevented by far-red light and ABA, and endosperm cap strength and nuclear DNA contents were not altered. Endo-β-mannanase activity of individual endosperm caps was not consistently related to their resistance to puncture. While internal free space is diagnostic for primed tomato seeds and occurs in a fraction of sitw seeds, it is not predictive of many aspects of germination physiology.
Desiccation sensitivity and activities of free radical-scavenging enzymes in recalcitrant Theobroma cacao seeds
Authors: Li Changrun , Sun Wendell Q.
Published: May 2019

Mature and immature axes of Theobroma cacao (cocoa) seeds tolerated desiccation under a rapid-drying regime to critical water contents of 1.0 and 1.7 g g-1 dw, respectively. These critical water contents corresponded to water contents below which activities of free radical-scavenging enzymes (ascorbate peroxidase, peroxidase and superoxide dismutase) decreased rapidly during desiccation. The decline in axis viability below the critical water content was correlated with sharp increases in lipid peroxidation and cellular leakage. Cotyledon tissues were more desiccation-tolerant than axes, with a low critical water content of 0.24 g g–1dw. Desiccation sensitivity in cotyledon tissues was also correlated with the decrease in superoxide dismutase activity and increased lipid peroxidation products. However, in the cotyledons, no ascorbate peroxidase activity was detected at any water content, and peroxidase activity was gradually reduced as desiccation proceeded. Cocoa embryonic axes contained large amounts of sucrose, raffinose and stachyose but only traces of reducing monosaccharides. Desiccation sensitivity of recalcitrant cocoa axes did not appear to be due to the lack of sugar-related protective mechanisms during desiccation, and it was more likely related to the decrease of enzymic protection against desiccation-induced oxidative stresses.
Triage, Transportation, and Destination Decisions by Out-of-Hospital Emergency Care Providers
Authors: Billittier Anthony J. , Lerner E. Brooke , Moscati Ronald M. , Young Gregory
Published: May 2019

Introduction:

The effectiveness of a tiered emergency medical services system often hinges upon the ability of initial care providers with little or no formal training to identify emergent patient needs and determine the best means to meet those needs.

Objectives:

To determine if out-of-hospital emergency care providers consistently make appropriate triage, transportation, and destination decisions; and to determine if experience and training have an effect on these decisions.

Methods:

A survey consisting of 14 patient-care scenarios was administered to certified and non-certified out-of-hospital emergency-care providers (n = 311) from 20 randomly selected EMS agencies. These agencies were part of EMS systems that utilize one, two, and three tiered responses by ambulance and fire-based commercial, municipal, and volunteer agencies. Participants were asked to select the most appropriate mode of transport and destination facility using the assumption that they had responded to each scenario in a basic life support ambulance. Answers included transporting the patient to various receiving facilities or requesting a more advanced-level unit to respond to the scene. Transport times to receiving facilities and estimated times of arrival for advanced-level units were provided with each choice. Eight emergency physicians unanimously had agreed upon the most appropriate answer for each scenario. A two-tailed t-test was used to compare the scores of the certified and non-certified groups; and Spearman's Correlation Coefficients were used to test the effects of experience and training.

Results:

Non-certified providers (n = 108) had a mean score of 32.6% or 4.6 (SD = 1.84) correct answers; certified providers (n = 203) had a mean score of 41.1% or 5.76 (SD = 2.12) correct answers (p < 0.000001). Spearman's Correlation Coefficients were: 1) individual provider level - (0.3978); 2) agency provider level - (0.2741); 3) hours workea per week - (0.2505); 4) years in EMS - (- 0.0821); 5) commercial or volunteer provider - (0.2398); 6) agency call volume - (0.2012); 7) agency location - (0.0685), and 8) transporting versus non-transporting agency - (0.2523).

Conclusion:

A need exists for further education of out-of-hospital emergency care providers with respect to triage, transportation, and destination decisions. Provider experience and level of certification do not appear to affect these critical patient-care decisions.