Jeffrey Weidenhamer
Ashland University, Chemistry, Geology, and Physics, Faculty Member
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Integrated weed management in commercial wheat production is urgently needed due to increasing herbicide resistance and production costs. Benzoxazinoids (BXs), which include benzoxazinones and benzoxazolinones, are unique bioactive... more
Integrated weed management in commercial wheat production is urgently needed due to increasing herbicide resistance and production costs. Benzoxazinoids (BXs), which include benzoxazinones and benzoxazolinones, are unique bioactive metabolites produced by certain members of the Poaceae including maize, wheat, rye and some dicots. BXs play important roles in plant defence and are causal agents of allelopathic interference. We investigated the role of genetics, environment and crop growth stage on BX abundance in the roots and rhizoplane of selected commercial wheat cultivars, and quantified their microbial transformation products (aminophenoxazinones) in roots and rhizosphere soils. Cultivar trials of competitive wheat (Triticum aestivum L.) genotypes were conducted in two moderate to low rainfall (449–572 mm) locations in southeastern Australia in 2015 and 2016. Replicated shoot, root, rhizoplane, and rhizosphere soil samples were collected for metabolic profiling at selected crop phenological stages, extracted and further analysed for known benzoxazinoid metabolites by liquid chromatography coupled with high resolution mass spectrometry. Fifteen BXs and related microbially derived aminophenoxazinones were detected in wheat shoots, roots, rhizoplanes and rhizosphere soils in both years and locations. MBOA, HMBOA and HMBOA-Glc were the three most abundant BX metabolites in wheat tissues, with the heritage cultivar Federation producing the highest levels of MBOA. The phytotoxic aminophenoxazinones APO and AMPO were the most abundant BX microbial transformation products and were detected in wheat roots, rhizoplanes and rhizospheres. Abundance varied with cultivar, growth stage, location and year. Microbially-produced aminophenoxazinones generated from both heritage and modern wheat root exudates were detected and quantified in rhizosphere soils, with abundance dependent on cultivar, growth stage, and season. Concentrations of microbial metabolites APO, AMPO, and AAPO were higher in the rhizosphere of young wheat seedlings in contrast to that of mature plants suggesting that phenoxazinone production was upregulated early in the season. Our findings demonstrate that BX metabolites at all life stages of wheat potentially undergo rapid biotransformation to aminophenoxazinones under field conditions, resulting in ecologically relevant concentrations sufficient for weed suppression by certain wheat cultivars.
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In 2014–2016, replicated field trials were performed to evaluate mechanisms of weed suppression in Australian canola genotypes in moderate to low rainfall zones at Wagga Wagga (572 mm) and Condobolin (449 mm) NSW, respectively. In... more
In 2014–2016, replicated field trials were performed to evaluate mechanisms of weed suppression in Australian canola genotypes in moderate to low rainfall zones at Wagga Wagga (572 mm) and Condobolin (449 mm) NSW, respectively. In 2015–2016, a split plot design with and without trifluralin as the main plot and cultivar as the sub plot was employed for trials; in this experiment 8 cultivars including hybrid and open-pollinated cultivars were assessed. At each site, crop and weed growth were monitored at various phenological stages including early season, vegetative, grain-filling, harvest and post-harvest. Certain cultivars exhibiting early vigour and also the ability to intercept light due to leaf canopy structure were associated with increased suppression of in-crop weed growth in canola trials; in addition, improved post-harvest weed suppression was associated with the presence of remaining crop residues after harvest. Cultivars GT-50, Hyola 600RR and Hyola 50 were Field evaluatio...
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In 2014 and 2015, replicated field trials were performed at commercial paddocks in moderate to low rainfall zones at Wagga Wagga and Condobolin NSW, respectively. In 2014, a total of 11 winter wheat cultivars (Triticum aestivum L.)... more
In 2014 and 2015, replicated field trials were performed at commercial paddocks in moderate to low rainfall zones at Wagga Wagga and Condobolin NSW, respectively. In 2014, a total of 11 winter wheat cultivars (Triticum aestivum L.) representing four major breeding family lines grown in Australia were evaluated with 13 cultivars assessed in 2015. At each site, crop and/or weed growth were monitored at various stages of growth: early season (tillering), vegetative, grain filling, harvest and post-harvest. Significant differences between wheat cultivar and location were observed for crop biomass, early vigour, leaf area index (LAI), weed number, weed biomass, canopy architecture and yield in both 2014 and 2015. Differences in weed suppression were largely impacted by crop architecture and phenology early in the growing season. Cultivar competitive traits were also influenced by both genotype and environmental factors, as shown by clear differences in cultivar performance, yield and wee...
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Replicated and randomised wheat (Triticum aestivum L.) cultivar trials were conducted in moderate to low rainfall zones at Wagga Wagga and Condobolin NSW, respectively in 2014 to 2016. At each experimental site, crop and/or weed growth... more
Replicated and randomised wheat (Triticum aestivum L.) cultivar trials were conducted in moderate to low rainfall zones at Wagga Wagga and Condobolin NSW, respectively in 2014 to 2016. At each experimental site, crop and/or weed growth were monitored at selected growth stages including tillering, vegetative, grain filling, harvest and after crop harvest. In addition, shoots, roots, rhizoplane and bulk rhizosphere soil samples were collected. All shoot and root samples were extracted in methanol using Buchi automated high pressure extractor, while soil samples were extracted using a rotary shaker. Extracts were profiled for unique secondary plant products acting as allelochemicals for weed suppression, specifically benzoxazinoids (BXs), using liquid chromatograph coupled to a triple quadrupole mass spectrometer (UPLC-MS QQQ). In addition, non-targeted metabolomics analysis was performed to evaluate relative abundance of diverse metabolites using a quadrupole time-of-flight mass spect...
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Due to the rise of herbicide resistance, diverse weed management tools are required to ensure sustainable weed control. This chapter focuses on competitive cereal crops and cultural strategies for weed management, including the use of... more
Due to the rise of herbicide resistance, diverse weed management tools are required to ensure sustainable weed control. This chapter focuses on competitive cereal crops and cultural strategies for weed management, including the use of weed-suppressive cultivars, post-harvest crop residues, and cover crops for management of the weed seedbank and eventual weed suppression. It also addresses factors influencing the effect of allelopathy on weeds, including soil and environmental conditions which limit or intensify the efficacy of allelochemicals. The response of some weeds to secondary metabolites released by living cereal crops and/or crop residues (selectivity) is also reviewed. Finally, recommendations are given for future research, aiming to address the knowledge gap regarding the fate of these compounds in the environment and their role in important physiological processes in both plants and microbes in the soil rhizosphere.
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Herbicide resistance in weeds restricts control options, thereby escalating economic loss and threatening agricultural sustainability in cereal production. Field evaluation of the crop performance, competitive traits, and consequent weed... more
Herbicide resistance in weeds restricts control options, thereby escalating economic loss and threatening agricultural sustainability in cereal production. Field evaluation of the crop performance, competitive traits, and consequent weed suppressive potential of 13 commercial winter wheat (Triticum aestivum L.) cultivars was performed in central NSW Australia with a focus on the evaluation and modelling of above-ground interactions. In 2015 and 2016, replicated field trials were established with genetically diverse commercial wheat genotypes under moderate to low rainfall conditions in Wagga Wagga (572 mm) and Condobolin (437 mm) New South Wales, respectively. The heritage cultivar Federation and a commercial cultivar of winter cereal rye (Secale cereale L.) were included as known weed-suppressive controls. Crop and weed growth, as well as early vigour, leaf area index, and photosynthetically active radiation, were monitored at various crop phenological stages including early growth...
Research Interests: Agronomy, Biology, Phenology, Canopy, Cultivar, and 4 moreLeaf Area Index, Weed Control, Weed, and Crop
Research Interests: Agronomy, Biology, Agriculture, Cultivar, Weed Control, and 4 moreWeed, Crop, Crop Protection, and Canola
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Artisanal aluminum cookware releases lead and other metals that pose significant health risk for people in low and middle-income countries. Cookware is made from recycled engine and electronic appliance parts, cans, and other materials.... more
Artisanal aluminum cookware releases lead and other metals that pose significant health risk for people in low and middle-income countries. Cookware is made from recycled engine and electronic appliance parts, cans, and other materials. We obtained fourteen custom-made pots from Ghana, produced from seven different scrap aluminum sources. We sought to determine whether avoiding certain source materials could reduce leaching of metals. Cooking was simulated using dilute acetic acid and palm oil. Aluminum released from all pots exceeded recommended guidelines. Variable amounts of lead, cadmium, chromium, nickel and other metals were leached, with the most lead coming from auto radiators and mixed metals. Pots made from engine blocks did not yield detectable amounts of lead. All pots released potentially harmful concentrations of two or more metals. Selective scrap aluminum sourcing for recycled cookware does not avoid metal contamination of food, although some sources may release lower concentrations of certain metals.
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Research Interests: Chemical Ecology, Invasive Species, Allelopathy, Nutrient Cycling, Competitive advantage, and 15 moreBiological Sciences, Environmental Sciences, Herbicides, Invasive plants, Nutrient, Environmental Impact, CHEMICAL SCIENCES, Invasive Plant, Ecosystem, Ecosystem Function, Glycine, Native Species, Microbial community, nutrient cycle, and Biogeochemical Cycle
(1) Experimental plant populations were grown at varying densities and varying levels of phytotoxins in the soil to investigate the potential interacting influences of allelopathy and resource competition on plant response and... more
(1) Experimental plant populations were grown at varying densities and varying levels of phytotoxins in the soil to investigate the potential interacting influences of allelopathy and resource competition on plant response and yield-density relationships.(2) Experiments ...
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ABSTRACT Disposal of electronic waste is a growing problem. This article describes an experiment for nonmajors that was developed (i) to demonstrate the concept of atomic absorption (AA) to the students by qualitative screening of circuit... more
ABSTRACT Disposal of electronic waste is a growing problem. This article describes an experiment for nonmajors that was developed (i) to demonstrate the concept of atomic absorption (AA) to the students by qualitative screening of circuit board materials and (ii) to demonstrate the use of AA for quantitative analysis of environmental samples. Circuit board samples are digested in aqua regia and analyzed following dilution. This experiment provides an effective demonstration of the lead content of consumer products that students can readily identify with. For nonmajors, the lab provides a significant introduction to major quantitative techniques of environmental analysis. The experiment can readily be extended to projects for science majors in the general chemistry or analytical chemistry courses. The experiment can also easily be connected to discussions of the potential environmental hazards of unsafe disposal of used electronic equipment and discussion of the various public policy options for dealing with this growing problem. Keywords (Audience): First-Year Undergraduate / General
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ABSTRACT The aerial parts of Chrysoma pauciflosculosa (syn. Solidago pauciflosculosa) gave two new sesquiterpenes, (+)-β-turmerone and a bisabolane endoperoxide, together with the known (-)-α-trans-bergamotene and... more
ABSTRACT The aerial parts of Chrysoma pauciflosculosa (syn. Solidago pauciflosculosa) gave two new sesquiterpenes, (+)-β-turmerone and a bisabolane endoperoxide, together with the known (-)-α-trans-bergamotene and (+)-β-sesquiphellandrene. When exposed to air and light, (+)-β-turmerone and (+)-β-sesquiphellandrene gave oxidative degradation products, involving hydroperoxide intermediates. Photosensitized singlet oxygen reactions of (+)-β-turmerone provided a series of bisabolane-type endoperoxides. The structures of the natural compounds as well as those of the degradation products and derivatives were elucidated by chemical and spectroscopic methods, mainly NMR and MS. Aqueous solutions of (+)-β-turmerone,(+)-β-sesquiphellandrene and (-)-α-trans-bergamotene were tested for their effects on the germination and radicle growth of three Florida sandhill species, Rudbeckia hirta, Schizachyrium scoparium, Leptochloa dubia, as well as Lactuca sativa. (+)-β-Turmerone significantly inhibited germination of L. sativa, stimulated radicle growth of L. sativa and S. scoparium at the 10 M level, and mildly inhibited radicle growth of R. hirta, as did (+)-β-sesquiphellandrene. (-)-α-trans-Bergamotene stimulated germination of S. scoparium and L. sativa and significantly enhanced radicle growth of S. scoparium.
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Research Interests: Chemical Ecology, Carbon, Chemical, Allelopathy, Activated Carbon, and 15 moreBiological Sciences, Environmental Sciences, Lettuce, Indicator species, Nitrogen, Bioavailability, Laboratories, CHEMICAL SCIENCES, Ammonium Nitrate, Fertilization, Microbial Activity, Biological Indicators, Bioassays, Growth Inhibition, and Biological Assay
The aerial parts of Chrysoma pauciflosculosa (syn. Solidago pauciflosculosa) gave two new sesquiterpenes, (+)-β-turmerone and a bisabolane endoperoxide, together with the known (-)-α-trans-bergamotene and (+)-β-sesquiphellandrene. When... more
The aerial parts of Chrysoma pauciflosculosa (syn. Solidago pauciflosculosa) gave two new sesquiterpenes, (+)-β-turmerone and a bisabolane endoperoxide, together with the known (-)-α-trans-bergamotene and (+)-β-sesquiphellandrene. When exposed to air and light, (+)-β-turmerone and (+)-β-sesquiphellandrene gave oxidative degradation products, involving hydroperoxide intermediates. Photosensitized singlet oxygen reactions of (+)-β-turmerone provided a series of bisabolane-type endoperoxides. The structures of the natural compounds as
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Thesis (M.S.)--Louisiana State University, Baton Rouge, 1991. Vita. Includes bibliographical references (leaves 58-61). Abstract.
Allelopathy is a complex ecological phenomenon, and it has proven notoriously difficult to develop experimental methods that can distinguish the role of both chemical interference and resource competition on plant growth. This paper... more
Allelopathy is a complex ecological phenomenon, and it has proven notoriously difficult to develop experimental methods that can distinguish the role of both chemical interference and resource competition on plant growth. This paper discusses two promising new methodologies which can be used to study allelopathic interactions in the greenhouse and field. (a) Bioassays in which the density of the susceptible
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ABSTRACT The potential significance of allelopathy in plant communities The broadest definition of allelopathy encompasses both stimulatory and inhibitory biochemical interactions among plants at all levels of complexity, including... more
ABSTRACT The potential significance of allelopathy in plant communities The broadest definition of allelopathy encompasses both stimulatory and inhibitory biochemical interactions among plants at all levels of complexity, including microorganisms (Molisch 1937). Over the years, it has been proposed that beyond the direct or indirect chemical effects of a plant on its neighbors, allelopathy may also affect community-level processes such as succession, nitrogen cycling and community dynamics (Muller, 1966; Rice, 1984; White, 1994; Wardle et al. 1998). Muller (1966, p. 332) summarizes allelopathy's potential importance to plant communities: The significance of allelopathy to ecological theory is very great. Small quantities of toxins may be responsible for massive reductions in plant growth and in water or mineral absorptions and thus strongly influence microclimate. Traditional theories of competition, reaction, biomass proportions, energy flow, mineral cycling, and ecosystem organization are all liable to reevaluation where allelopathy is demonstrable. Elucidating allelopathic interactions has also been of interest for intensely practical reasons. Understanding this phenomenon could lead to the development of new herbicide chemistries, the use of allelopathic mulches, cover crops and cropping rotations to control weeds, the development of allelopathic crop varieties, and the control of soil sickness and replant problems resulting from autotoxicity (Gliessman, 1983; Duke and Lydon, 1988; Weston, 1996; Olofsdotter, 1998; Anaya, 1999; Birkett et al. 2001).
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ABSTRACT Four sesquiterpene lactones which share structural features of the lactone rings of strigol were tested as witchweed germination stimulants. Confertiflorin and parthenin significantly increased witchweed germination at 10−4 M,... more
ABSTRACT Four sesquiterpene lactones which share structural features of the lactone rings of strigol were tested as witchweed germination stimulants. Confertiflorin and parthenin significantly increased witchweed germination at 10−4 M, and parthenin and desacetylconfertiflorin increased germination at 10−5 M. Dihydroparthenolide induced 70% germination of witchweed across a concentration range of 10−7 to 10−9 M. This activity is comparable to the activity of strigol and its synthetic analogues.
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Chemical constituents of the perennial shrub Calamintha ashei have been characterized as part of our investigation of the allelopathic properties of this plant. Besides the known monoterpenes, (+)-evodone, (-)-calaminthone and... more
Chemical constituents of the perennial shrub Calamintha ashei have been characterized as part of our investigation of the allelopathic properties of this plant. Besides the known monoterpenes, (+)-evodone, (-)-calaminthone and (+)-desacetylcalaminthone, fresh aerial parts of C. ashei provided six new menthofurans, two new germacrane sesquiterpenes, and the six, known flavonoids: 5-desmethoxynobiletin, 5-hydroxy-6,7,8,4'-tetramethoxyflavone, 5,4'-dihydroxy-6,7,8,3'-tetramethoxyflavone, thymonin, 5,4'-dihydroxy-6,7-dimethoxyflavone and 6-hydroxy-7,3'-dimethoxyluteolin. The structures of the new compounds were elucidated by spectroscopic methods and comparison of their 1H NMR spectra with those of structurally related compounds. The molecular structures of (+)-evodone, 5-desmethoxynobiletin (5-hydroxy-6,7,8,3',4'-pentamethoxyflavone) and the triacetate of thymonin (7,8,3'-trimethoxy-5,6,4'-triacetoxyflavone), were determined by single crystal X-ray d...
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... of any allelochemicals present in the soil, even though some water-sol-uble compounds would be expected to leach away during ... 172 JD Weidenhamer and JT Romeo There is evidence that environmental factors are important in mediating... more
... of any allelochemicals present in the soil, even though some water-sol-uble compounds would be expected to leach away during ... 172 JD Weidenhamer and JT Romeo There is evidence that environmental factors are important in mediating the activity of scrub allelochemicals. ...
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... 194/John T. Romeo and Jeffrey D. Weidenhumer with 6-methoxy-2, 3-benzoxazolinone (MBOA) also yielded AZOB as well as its mono-(MAZOB) and dimethoxy ... 199 Ib). In summary, primary allelochemicals from rye, DIBOA and BOA, were shown... more
... 194/John T. Romeo and Jeffrey D. Weidenhumer with 6-methoxy-2, 3-benzoxazolinone (MBOA) also yielded AZOB as well as its mono-(MAZOB) and dimethoxy ... 199 Ib). In summary, primary allelochemicals from rye, DIBOA and BOA, were shown to be able to leach into the soil. ...