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A G McKenzie‐Gopsill S Amirsadeghi H J Earl A M P Jones L Lukens E Lee C J Swanton 《Weed Research》2019,59(4):288-299
The mechanisms by which weeds compete with crop plants are poorly understood. To gain insight into these mechanisms, we characterised early physiological responses of soyabean to neighbouring weeds using a biological weedy system that generated a consistent far‐red‐enriched light environment and excluded direct resource competition. Neighbouring weeds decreased superoxide dismutase activity in unifoliate leaves. This coincided with increased hydrogen peroxide (H2O2) and oxidized ascorbate levels, while the steady‐state level of superoxide, catalase activity and lipid peroxidation remained unchanged. These responses suggested increased leaf production of singlet oxygen (1O2), which was demonstrated by detection of increased Singlet Oxygen Sensor Green (SOSG) fluorescence within 3 h after staining of unifoliate leaves. This finding was further supported by increased ratios of the photosensitiser protochlorophyllide to both chlorophyllide a, and total chlorophyll in the dark as well as enhanced sensitivity to cell death by a 1O2‐generating compound in the light. These responses coincided with dramatic changes in photosynthesis, carbon partitioning and biomass allocation with a persistent decline in leaf sucrose level and biomass production at later growth stages. This study provides direct experimental evidence that under resource‐independent competition, far‐red‐enriched light reflected by neighbouring weeds can alter the balance between ROS production and detoxification and thereby generate an oxidative stress signal in soyabean leaves. 相似文献
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Plants are sessile organisms that have evolved various mechanisms to adapt to complex and changing environments. One important feature of plant adaption is the production of specialised metabolites. Terpenes are the largest class of specialised metabolites, with over 80 000 structures reported so far, and they have important ecological functions in plant adaptation. Here, we review the current knowledge on plant terpenes that mediate below‐ground interactions between plants and other organisms, including microbes, herbivores and other plants. The discovery, functions and biosynthesis of these terpenes are discussed, and prospects for bioengineering terpenoids for plant protection are considered. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献
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MOHAMMAD AMZAD HOSSAIN YUKIO ISHIMINE HITOSHI KURAMOCHI HIKARU AKAMINE 《Weed Biology and Management》2002,2(3):153-158
The present study was undertaken from May 1996 to October 1997 in the glasshouse of the University of the Ryukyus, Okinawa, Japan to investigate standing water (12 cm deep) and shoot removal plus standing water regimes on morphological changes, growth, regrowth and biomass production of torpedograss ( Panicum repens L.). The stem internode was longer in standing-water-treated plants than that in untreated plants. The root-crown was developed from the submerged stem-node. Spike-like tillers and sheath-like leaf blades were observed in water-treated plants. Higher shoot biomass and lower rhizome biomass were obtained in standing-water-treated plants than that in untreated plants. Standing-water-treated plants attained higher total biomass than untreated plants. Standing-water stress was the factor that inhibited regrowth of torpedograss when the above-ground shoot was removed. Rhizomes without shoots of 6-month-old torpedograss did not survive in standing water for more than 6 months. The results indicate that torpedograss can survive in standing water if the shoots remain above the water surface. Shoot removal is one effective way to control torpedograss regrowth in standing water. The results of this study may be dependent on season, day length, water temperature, water pH, water depth and salt concentration in water. 相似文献
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The adsorption processes of carbofuran from an aqueous solution have been determined at the solid–liquid interface, onto silica and at liquid–vapour interfaces. At the solid–liquid interface, the adsorption isotherms and their evolution with temperature reveal that adsorption is generally weak but increases with temperature. Adsorption also significantly increases with concentration when the solubility limit is approached. The study at the liquid–vapour interface reveals that adsorption at this interface is 70 times larger than at the solid–liquid interface. Again, adsorption values at the liquid–vapour interface increase with temperature (below 30°C) and near the solubility limit. Consequences of the observations on the behaviour of carbofuran in the environment are discussed. © 1998 SCI 相似文献
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Light is an important resource that crops and weeds compete for and so increased light interception by the crop can be used as a method of weed suppression in cereal crops. This research investigated the impact of altered availability of photosynthetically active radiation (PAR) (from crop row orientation or seeding rate) on the growth and fecundity of Lolium rigidum. Wheat and barley crops were sown in an east–west (EW) or north–south (NS) direction, at a high or low seeding rate, in three field trials in 2010 and 2011 (at Merredin, Wongan Hills and Katanning, Western Australia). The average PAR available to L. rigidum in the inter‐row space of EW crops compared with NS crops was 78% to 91% at crop tillering, 39% to 56% at stem elongation, 28% to 53% at boot/anthesis and 41% to 59% at grain fill. Reduced PAR in the EW crop rows resulted in reduced L. rigidum fecundity in five of the six trials (average of 2968 and 5705 L. rigidum seeds m?2 in the EW and NS crops). Availability of PAR was not influenced by seeding rate, but the high seeding rate reduced fecundity in three of the six trials (average of 3354 and 5092 seeds m?2 in the crops with high and low seeding rate). Increased competitive ability of crops (through increased interception of PAR or increased crop density) was highly effective in reducing L. rigidum fecundity and is an environmentally friendly and low cost method of weed suppression. 相似文献
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Non‐chemical weed control on pavements needs more frequently repeated treatments than the application of glyphosate and often uses large amounts of fuel. To obtain effective hot water control with minimum energy consumption, an in‐depth study of efficacy‐influencing factors was performed. Three dose–response pot experiments were conducted outdoors to investigate the impact of growth stage (39, 60 and 81 day old), water temperature (78, 88 and 98°C), time of the day (2, 7 and 12 h after sunrise) and treatment interval (2, 3, 4 and 6 week intervals) on hot water sensitivity of seven weed species that are hard to control on pavements. Responses to hot water were quantified by weed coverage and total dry biomass. In general, hot water sensitivity was highest for species with large planophile leaves and lowest for grasses with small erectophile leaves. Most species were twofold to sixfold more sensitive to water at 98°C than at 78 and 88°C, particularly when treated at early growth stages. Among treatment intervals, treating at 3‐week intervals was up to twofold more effective and energy efficient than treating at 6‐week intervals. Sensitivity was about twofold lower in the morning than in the afternoon. For effective control of weeds, while using less fuel, it is recommended to apply hot water in the late afternoon, to operate at high water temperature (98°C) and to treat plants as young as possible at 3‐week intervals. 相似文献
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Tina Tind Tenna J Mathiesen Jens E Jensen Christian Ritz Jens C Streibig 《Pest management science》2009,65(11):1257-1262
BACKGROUND: Grass seed crops are minor crops that cannot support the development of selective herbicides for grass weed control in grass seed crops. An option is to screen for selective herbicides with the use of logarithmic spraying technology. The aim of this paper is to assess selectivity of various herbicides in grass seed crops by using dose–response curves. RESULTS: Six grass species were subjected to logarithmic spraying with 11 herbicides and with Poa pratensis L. as a weed. The ratio between the doses that caused 10% of damage to the crop and 90% of damage to the weed was used as a selectivity index. Compounds with selectivity indices above 2 can be safely used in a crop. The two ACCase herbicides clodinafop‐propargyl and fenoxaprop‐P‐ethyl and a mixture of the two ALS herbicides mesosulfuron and iodosulfuron could be used selectively to control P. pratensis in Festuca rubra L., although the selectivity indices in no instances were greater than the desired 2.0. CONCLUSION: The logarithmic sprayer can be a rapid screening tool for identifying compounds with favourable selectivity indices. Good experimental design is needed to alleviate rates being systematically distributed and confounded with growth rate and soil fertility gradients. Copyright © 2009 Society of Chemical Industry 相似文献
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Direct and host‐mediated interactions between Fusarium pathogens and herbivorous arthropods in cereals 
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下载免费PDF全文 Fusarium head blight and fusarium ear rot diseases of cereal crops are significant global problems, causing yield and grain quality losses and accumulation of harmful mycotoxins. Safety limits have been set by the European Commission for several Fusarium‐produced mycotoxins; mitigating the risk of breaching these limits is of great importance to crop producers as part of an integrated approach to disease management. This review examines current knowledge regarding the role of arthropods in disease epidemiology. In the field, diseased host plants are likely to interact with arthropods that may substantially impact the disease by influencing spread or condition of the shared host. For example, disease progress by Fusarium graminearum can be doubled if wheat plants are aphid‐infested. Arthropods have been implicated in disease epidemiology in several cases and the evidence ranges from observed correlations between arthropod infestation and increased disease severity and mycotoxin accumulation, to experimental evidence for arthropod infestation causing heightened pathogen prevalence in hosts. Fusarium pathogens differ in spore production and impact on host volatile chemistry, which influences their suitability for arthropod dispersal. Herbivores may allow secondary fungal infection after wounding a plant or they may alter host susceptibility by inducing changes in plant defence pathways. Post‐harvest, during storage, arthropods may also interact with Fusarium pathogens, with instances of fungivory and altered behaviour by arthropods towards volatile chemicals from infected grain. Host‐mediated indirect pathogen–arthropod interactions are discussed alongside a comprehensive review of evidence for direct interactions where arthropods act as vectors for inoculum. 相似文献
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Could recent increases in atmospheric CO2 have acted as a selection factor in Avena fatua populations? A case study of cultivated and wild oat competition 下载免费PDF全文
下载免费PDF全文 L H Ziska 《Weed Research》2017,57(6):399-405
Projected increases in atmospheric carbon dioxide concentration [CO2] may lead to differential selection and competition between weeds and crops. Yet, the current level of atmospheric [CO2] already reflects a rapid rise (~25%) from mid‐20th century levels. To assess whether this increase could have already resulted in differential selection between weeds and crops, two temporally distinct populations of Avena fatua (wild oat) from the same geographic location, one from the 1960s (WOold) and one from 2014 (WOnew), were grown with and without a cultivated oat (CO) line, Clintland 64 (Avena sativa) at current and mid‐20th century [CO2] levels (ca 320 and 402 μmol mol?1 respectively). Monocultures of each WO population differed in their response to recent increases in atmospheric [CO2], with WOnew showing a significantly higher response for all vegetative parameters relative to WOold. Assessment of competitive outcomes indicated that at 315 μmol mol?1 cultivated oat was at a competitive advantage relative to either A. fatua population for leaf area and total above‐ground biomass. However, at current levels of CO2, an overall increase in WOnew competitive ability was observed relative to the cultivated oat line. Overall, these differences are consistent with, but not conclusive for, improved evolutionary fitness and increased early competitive ability of A. fatua relative to cultivated oat as a function of the recent increase in atmospheric [CO2]. While additional empirical studies are needed, these preliminary results indicate that weeds may be adapting rapidly to rising levels of atmospheric carbon dioxide. 相似文献
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BACKGROUND: Twenty‐three isolates of Metarhizium anisopliae (Metschnikof) Sorokin and M. acridum (Driver & Milner) JF Bischoff, Rehner & Humber from non‐aphid host insects around the globe were evaluated for their aphid biocontrol potential, which is not well known. RESULTS: The apterous adults of green peach aphid Myzus persicae (Sulzer) were exposed to the fungal sprays of 11.5, 99 and 1179 conidia mm?2 and blank control in three leaf‐dish bioassays. All the tested isolates except one were proven to be infective to the aphid species at 21 ± 1 °C and 14:10 h light:dark photoperiod, causing corrected mortalities of 10.1–95.3% at the high spore concentration. The data from ten isolates causing > 50% mortality at the high concentration were found to fit a time–concentration–mortality model well, yielding parameters for the estimates of their LC50 and LT50 that vary with post‐spray time and spore concentration respectively. Four isolates of M. anisopliae (ARSEF 759, 4132, 2080 and 576) had LC50 values of 44–80 conidia mm?2 on day 8 and LT50 values of 4.9–6.8 days at 100 conidia mm?2, with 91–98% of the killed aphids being well mycotised after death. CONCLUSION: The Metarhizium infectivity to M. persicae differs greatly among the tested isolates. The four mentioned isolates with desired virulence and sporulation potential are excellent candidates for microbial control of aphids. Copyright © 2010 Society of Chemical Industry 相似文献
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Cropping systems modify soil biota effects on wheat (Triticum aestivum) growth and competitive ability 下载免费PDF全文
下载免费PDF全文 Plants alter soil biota which subsequently modifies plant growth, plant–plant interactions and plant community dynamics. While much research has been conducted on the magnitude and importance of soil biota effects (SBEs) in natural systems, little is known in agro‐ecosystems. We investigated whether agricultural management systems could affect SBEs impacts on crop growth and crop–weed competition. Utilising soil collected from eight paired farms, we evaluated the extent to which SBEs differed between conventional and organic farming systems. Soils were conditioned by growing two common annual weeds: Amaranthus retroflexus (redroot pigweed) or Avena fatua (wild oat). Soil biota effects were measured in wheat (Triticum aestivum) growth and crop–weed competition, with SBEs calculated as the natural log of plant biomass in pots inoculated with living soil divided by the plant biomass in pots inoculated with sterilised soil. SBEs were generally more positive when soil inoculum was collected from organic farms compared with conventional farms, suggesting that cropping systems modify the relative abundance of mutualistic and pathogenic organisms responsible for the observed SBEs. Also, as feedbacks became more positive, crop–weed competition decreased and facilitation increased. In annual cropping systems, SBEs can alter plant growth and crop–weed competition. By identifying the management practices that promote positive SBEs, producers can minimise the impacts of crop–weed competition and decrease their reliance on off‐farm chemical and mechanical inputs to control weeds, enhancing agroecosystem sustainability. 相似文献
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Noritada Matsuo 《Pest management science》1998,52(1):21-28
The three commercial synthetic pyrethroids containing a carbon–carbon triple bond, α-ethynyl-2-methylpent-2-enyl (1R)-trans-chrysanthemate, (S)-2-methyl-4-oxo-3-(2-propynyl)cyclopent-2-enyl (1R)-trans,cis-chrysanthemate and [2,5-dioxo-3-(2-propynyl)-1-imidazolidinyl]methyl (1R)-trans-chrysanthemate are reviewed with emphasis on their inventive histories. Their chemistry and efficacy are described briefly. The relationship between stereochemistry and the biological activity is also discussed. © 1998 SCI. 相似文献
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A simple, effective and convenient laboratory leaf system was developed to detect transmission of Iris yellow spot virus (IYSV) by thrips. It was shown that IYSV was transmitted highly efficiently by adults and also by larvae of five thelytokous populations of Thripstabaci from distinct areas in Japan: over all these populations, transmission efficiency of adults ranged from 20·4% (19/93) to 41·1% (76/185) and that of larvae from 17·3% (14/81) to 44·1% (67/152). Finally, it was demonstrated that IYSV infection was not detrimental to the development and fecundity of thrips until early adulthood. Larval mortalities of virus‐exposed thrips were higher than in their unexposed counterparts in all three populations, but the differences were not significant. The results demonstrated that T. tabaci populations have considerable potential to cause outbreaks of IYSV and spread the disease because of their efficient transmission of the virus. 相似文献
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Kazuo Yagi Kazuhiko Akimoto Norihiko Mimori Toshiro Miyake Masaki Kudo Kazutaka Arai Shigeru Ishii 《Pest management science》2000,56(1):65-73
A series of novel 3‐(2,4,6‐trisubstituted phenyl)uracil derivatives has been synthesised and assayed for insecticidal/acaricidal activity. The assay indicated certain requirements for optimal insecticidal activity, which can be summarised as follows: (a) the substituents on the phenyl ring should possess hydrophobicity and electron‐withdrawing properties, and the sum of their volumes determines the level of activity; (b) the substituent at the 6‐position on the uracil ring should also possess electron‐withdrawing properties and hydrophobicity, together with the correct volume; (c) the 1‐position on the uracil ring should be unsubstituted for activity against Nephotettix cincticeps and Epilachna vigintioctopunctata, but substituents with length C3 to C4 may be optimal for activity against Tetranychus urticae; (d) certain substituents at the 5‐position of the uracil ring give activity against E vigintioctopunctata and T urticae, but not against N cincticeps; (e) a thiocarbonyl group at the 2‐position of the uracil ring is less effective than a carbonyl group. Of the compounds assayed, 3‐(2,6‐dichloro‐4‐trifluoromethylphenyl)‐6‐trifluoromethyluracil showed high activity against all the species assayed. © 2000 Society of Chemical Industry 相似文献