Chalcone suppresses lignin biosynthesis in illuminated soybean cells

Lignin and its related metabolites play critical roles in plant growth and development. Thus, lignin biosynthesis has attracted interest as a novel target site of plant growth inhibitors. Chalcone has been shown to not only inhibit lignin biosynthesis in plants, but also to suppress the growth of many annual plant species. In order to know the direct effect of chalcone on plant metabolism, the effects of chalcone on the activities of key enzymes in lignin biosynthesis and on the related metabolites were clarified with a time‐course study by using light‐induced suspension cultures of soybean cells. The fresh weight and packed cell volume of the soybean cells were inhibited after 8 h of chalcone treatment. The activities of phenylalanine ammonia lyase (EC 4.3.1.24) and 4‐coumarate: coenzyme A ligase (4CL; EC 6.2.1.12) were largely inhibited 4 h after the treatment with 0.15 mmol L^?1 chalcone. Unlike these two enzymes, the activity of cinnamyl alcohol dehydrogenase (EC 1.1.1.195) was not inhibited until 16 h after the chalcone treatment. The content of the 4CL substrates and lignin in the soybean cells became relatively lower than the control under the light condition within 4 h and 8 h after the chalcone treatment, respectively. These results suggest that the growth suppression of soybean cells is positively associated with the inhibition of lignin biosynthesis by exogenous chalcone.     

Effect of naringenin on the growth and lignin biosynthesis of gramineous plants

Lignin biosynthesis is essential for plant growth. 4‐Coumarate CoA ligase (4‐CL, EC6.2.1.12) is involved in the monolignol synthesis and occupies a key role in regulating carbon flow into the phenylpropanoid metabolism pathway. Naringenin, one of the metabolites in this pathway, is known as a potent in vitro inhibitor of 4‐CL. The growth of rice (Oryza sativa L. cv. Koshihikari), maize (Zea mays L. cv. Yellow corn) and Echinochloa oryzicola Vasing seedlings at the 2nd leaf stage was inhibited after continuous root application with 0.1 mmol L^?1 naringenin for 1 week, although naringenin did not kill these gramineous plants. The highest inhibition of fresh weight increase was observed in maize, followed by rice and E. oryzicola. The symptoms in these plants were root browning, delay of leaf/root development and shoot dwarfing. Naringenin treatment increased the contents of 4‐CL substrates, cinnamic acid, 4‐coumaric acid, caffeic acid and ferulic acid from 1.2 to 7.2 times and from 1.2 to 3.5 times in shoots and roots, respectively, except for ferulic acid in E. oryzicola roots. It also caused a slight decrease of the lignin content and alteration of lignin constitutions in rice plants. These results suggested that the monolignol pathways after 4‐CL towards lignin has the possibility to be the novel action sites of plant growth retardants, although further investigations are needed to clarify the mode of action.     

Selective growth suppression of five annual plant species by chalcone and naringenin correlates with the total amount of 4-coumarate: coenzyme A ligase

The 4-coumarate: coenzyme A ligase (4CL) is one of the key enzymes in the biosynthesis of lignin monomers. It has been demonstrated that the 4CL is a new potential target site for developing effective plant growth inhibitors. Although previous studies demonstrate that chalcone and naringenin differentially suppress the growth of several annual plant species, we show here that the compounds can inhibit the 4CL enzyme activity in the plants. The enzyme was extracted and partially purified from the leaf tissues of two tolerant plants (wheat and soybean) and three susceptible plants (tomato, barnyard grass, and common chickweed). A maximal 29-fold purification of the enzyme, with a yield of 32% (tomato), was achieved by a six-step procedure, including anion-exchange column chromatography. Naringenin strongly inhibited the 4CL specific activity in wheat, soybean and barnyard grass, whereas chalcone showed the highest inhibitory effect in common chickweed. A good correlation was observed between the level of growth suppression by the compounds and the total 4CL amount in the plants. These results suggest that the inhibitor treatment at the same concentration could not inactivate the entire 4CL enzyme produced in the tolerant plants. Taken together, these results highlight the possibility of the 4CL as a new action site of growth suppression.     

Competition between maize and Datura stramonium in an irrigated field under semi-arid conditions

Crop growth of maize ( Zea mays L.) and Datura stramonium L. in monoculture and competition was studied over 4 years in a flood irrigated field in Zaragoza (Spain). Plant density was 8.33 m^–2 for maize and 16.66 m^–2 (1994 and 1995) and 8.33 m^–2 (1996 and 1997) for D. stramonium . Maize yield was decreased by 14–63% when competing with the weed. Yield reduction increased as the time between crop and weed emergence decreased. The development of leaf area per plant during the exponential growth phase was faster in maize primarily because the leaf area of maize seedlings at emergence time was greater than that of the weed. The faster growth of maize in leaf area and height reduced the photosynthetically active radiation received by the weed. Datura stramonium had a lower radiation use efficiency (RUE) than maize. Competition from the weed slightly decreased the maximum leaf area index (LAI) of the crop, and leaf senescence of maize was accelerated. The weed competed with the crop late in the season reducing crop growth rate, grain number per ear and grain weight. Competitive ability of D. stramonium for light was mainly due to its growth habit, with the leaves concentrated in the upper part of the canopy (more than 75% of LAI in the upper 25% of its height), its higher light extinction coefficient (0.89) and its indeterminate growth habit. The N plant content of maize was not influenced by the presence of the weed. The weed had a higher N plant content than the crop throughout the season and took up more N in monoculture.     

Enhanced field control of wheat take-all using cold tolerant isolates of Gaeumannomyces graminis var. graminis and Phialophora sp. (lobed hyphopodia)

Cold tolerant isolates of Gaeumannomyces graminis var. graminis ( Ggg ) and Phialophora sp. (lobed hyphopodia), which produced at least comparable growth rates at 5°C to those of pathogenic G. graminis var. tritici ( Ggt ), were shown to control take-all disease in wheat effectively in 2 years of field experiments in New South Wales, Australia. The addition of oat inoculum of these fungi at the rate of 60 kg/ha to the seeding furrow significantly ( P  ≤ 0.05) reduced disease and increased grain yields by 33–45% compared to the Ggt alone treatment. The use of 30 kg/ha of oat inoculum also significantly ( P  ≤ 0.05) reduced disease and increased grain yields by 21–44%. These high levels of take-all control were obtained consistently from four field experiments on three different soil types with different pHs. A treatment inoculated with Ggg alone showed no disease symptoms and produced grain yields similar to that of untreated wheat. This fungus is, therefore, non-pathogenic to wheat. At high rates of inoculation of Ggg and Phialophora sp. (lobed hyphopodia), 65–80% of tillering wheat plants (GS 32) had root systems colonized by these fungi. In contrast, two Pseudomonas spp. and an isolate each of Ggg and Phialophora sp. (lobed hyphopodia), which did not grow at 5°C, were ineffective in controlling take-all. Take-all assessments during heading (GS 61-83) were highly correlated ( R ²=0.6047, P ≤0.0005) with the relative yield increase or decrease of inoculated treatments compared to the Ggt alone treatment. The use of a Ggg isolate (90/3B) and a Phialophora sp. (lobed hyphopodia) isolate (KY) for take-all control has been patented. These fungi are being developed for commercial use.     

An integrated approach to control glyphosate‐resistant Ambrosia trifida with tillage and herbicides in glyphosate‐resistant maize

Glyphosate‐resistant Ambrosia trifida is a competitive and difficult‐to‐control annual broad‐leaved weed in several agronomic crops in the Midwestern United States and Ontario, Canada. The objectives of this study were to compare treatments for control of glyphosate‐resistant A. trifida with tillage followed by pre‐emergence (PRE) and/or post‐emergence (POST) herbicides in glyphosate‐resistant maize and to determine the impact of A. trifida escapes on maize yield. Field experiments were conducted in 2013 and 2014 in grower fields infested with glyphosate‐resistant A. trifida. Tillage prior to maize sowing resulted in 80–85% control compared with no tillage. Tillage followed by PRE application of saflufenacil plus dimethenamid‐P with or without atrazine resulted in 99% control compared with ≤86 and 96% control with PRE herbicides alone at 7 and 21 days after application respectively. Tillage or POST‐only herbicides resulted in 4–14 A. trifida plants m^?2, whereas a PRE and POST programme had <3 plants m^?2. Maize yield was greatest (13.1–14.2 tonnes ha^?1) with tillage followed by PRE and POST herbicide programme. The relationship between maize yield and late‐season density of A. trifida escapes showed a 50% maize yield reduction irrespective of control measures when A. trifida density was 8.4 plants m^?2. It was concluded that the combination of tillage with PRE and/or POST herbicides reduced A. trifida density and biomass accumulation early in the season and provided an integrated approach for effective management.     

Competition between Imperata cylindrica and maize in the forest savannah transition zone of Nigeria

Imperata cylindrica is a noxious weed that infests annual and perennial crops in most tropical regions. High crop densities may offer opportunities to reduce I. cylindrica competition in small‐scale farming systems. The competitive ability of maize relative to I. cylindrica was evaluated in an addition series experiment in the forest savannah transition zone in 2006 and 2007 at Ibadan, Nigeria. Maize and I. cylindrica were planted in eight monoculture densities (4, 8, 12, 16, 20, 32, 48 and 64 plants m^?2) and in a 1:1 mixture at eight total densities (2:2, 4:4, 6:6, 8:8, 10:10, 16:16, 24:24 and 32:32 maize: I. cylindrica plants m^?2) as in monoculture. Non‐linear regression models were used to relate crop and weed shoot biomass to their densities and total grain yield to maize density. In maize, intraspecific competition was more than interspecific competition; in I. cylindrica, interspecific competition was higher than intraspecific. As expected, total grain yield was lower in the mixture than in maize monoculture at all total densities. Average maize grain yield in maize monoculture differed from that in mixtures by 0.77 t ha^?1 in 2006 and 0.57 t ha^?1 in 2007. Niche differentiation indices were <1 in 2006 and >1 in 2007, indicating that both species competed for similar resources in 2006, but not in 2007. The greater competitive ability of maize over I. cylindrica may be associated with rapid growth and canopy development observed in the field.     

Responses of otebo bean (Phaseolus vulgaris L.) to postemergence herbicides

Ontario otebo bean growers have few herbicide options available for weed management. Six field trials were conducted in Ontario, Canada, over a 2 year period (2003 and 2004) to evaluate the tolerance of otebo bean to the postemergence (POST) application of bentazon at 1080 and 2160 g ai ha⁻¹, fomesafen at 240 and 480 g ai ha⁻¹, sethoxydim at 500 and 1000 g ai ha⁻¹, quizalofop-p-ethyl at 72 and 144 g ai ha⁻¹, imazamox plus fomesafen at 25 + 200 and 50 + 400 g ai ha⁻¹, and imazamox plus bentazon at 25 + 600 and 50 + 1200 g ai ha⁻¹. All treatments, including the untreated control, were maintained weed-free during the growing season. The POST application of bentazon, imazamox plus fomesafen, and imazamox plus bentazon caused as much as 9% visual injury and reduced the plant height ≤ 12%, reduced the shoot dry weight ≤ 32%, and delayed maturity but had no adverse effect on the yield of otebo bean. Fomesafen, sethoxydim, and quizalofop-p-ethyl applied POST caused as much as 8% visual injury but this was transient and had no adverse effect on the plant height, shoot dry weight, seed moisture content, and yield of otebo bean, except for quizalofop-p-ethyl, which reduced the shoot dry weight as much as 18%. Based on these results, bentazon, fomesafen, sethoxydim, quizalofop-p-ethyl, imazamox plus fomesafen, and imazamox plus bentazon applied POST have an adequate margin of crop safety for weed management in otebo bean production in Ontario. However, care must be taken to avoid spray overlaps to prevent injury from bentazon, imazamox plus fomesafen, and imazamox plus bentazon.     

Sulcotrione soil persistence and mobility in summer maize and winter wheat crops

Sulcotrione soil persistence in spring maize ( Zea mays L.) crops grown on a sandy loam soil was greater at pH 5·5 and 6·0 (soil half-life T _1/2≈58 days) than at pH 7·1 ( T _1/2 = 44 days). Sulcotrione was also applied as recommended on a summer maize crop at the five- to six-leaf growth stage, grown on a sandy loam soil. Sulcotrione soil half-life was 44 days, and the herbicide remained mainly in the 0- to 5-cm surface soil layer during the cropping period, in spite of the high water solubility and the heavy rains at the end of August; lower sulcotrione concentrations (10–18% of the total during the 2-month period after sulcotrione application) were detected in the 5- to 10-cm surface soil layer. The herbicide was applied pre-emergence to winter wheat ( Triticum aestivum L.) at four sites that differed in their soil texture and composition: loamy sand, sandy loam, loam and clay loam. Persistence was greater in the soils containing more organic matter. In soils having similar organic matter contents, persistence was lower in the soil containing more sand relative to loam and clay. During the winter crops, sulcotrione moved down to the 10- to 15-cm soil layer, in spite of the fact that the rains were lower in winter than in summer. Sulcotrione most generally was not detected in the 15–20 cm soil layer of the maize and winter wheat crops.     

活性氧与木质素对细菌Sneb825诱导番茄抵抗南方根结线虫侵染的响应

 根结线虫病严重威胁各类蔬菜作物的生产,是世界上最难防治的土传病害之一。利用生防细菌能够有效地控制蔬菜根结线虫种群数量并降低危害。荧光假单胞菌Sneb825是本实验室筛选出的对南方根结线虫病具有较高防效的生防细菌。本研究通过盆栽试验、裂根试验和温室试验验证了荧光假单胞菌Sneb825诱导番茄抗南方根结线虫侵染的防治效果;通过酶联免疫法(ELISA)和实时荧光定量PCR检测了番茄根系内活性氧与木质素含量及其相关基因表达量的变化。研究发现,Sneb825菌株发酵液不但能够有效降低南方根结线虫对番茄的侵染,而且对番茄植株有显著的促生作用。Sneb825菌株发酵液灌根处理并接种南方根结线虫二龄幼虫后,番茄根系内活性氧(10 dpi)和木质素含量(5 dpi)显著高于空白对照;活性氧合成相关基因RBOH1(10 dpi)和过氧化物酶基因Ep5C(10 dpi)以及木质素合成相关基因Tpx1(5 dpi)的表达量均达到最高值。研究结果表明活性氧和木质素的大量积累是荧光假单胞菌Sneb825诱导番茄抑制南方根结线虫侵染的防御对策之一。荧光假单胞菌可以有效的防治根结线虫病,在农业生产实践中具有潜在的应用前景。     

Effect of amitrole and 2,4-D applied preplant and pre-emergence in soybean (Glycine max)

There is limited information on the effect of amitrole and 2,4-D ester applied preplant and pre-emergence in soybean (G lycine max L.) in Ontario, Canada. Six field trials were conducted over a 2 year period (2004 to 2005) at three Ontario locations to evaluate the response of soybean to amitrole or 2,4-D ester applied at 14 days preplant (DPP), 7 DPP, 1 day after planting (DAP), and 7 DAP. The application of amitrole resulted in as much as 5.8, 3.9, 1.7, and 1% visible crop injury in soybean at 7, 14, 28, and 56 days after emergence (DAE), respectively. There was no visible injury in soybean with any amitrole treatment at 56 DAE, except for amitrole applied at 7 DAP, which caused 1% visible injury in soybean at 2310 g ha⁻¹. The application of the 2,4-D ester caused ≤8.3, 9.7, 4.6, and 1.3% visible injury in soybean at 7, 14, 28, and 56 DAE, respectively. The visible injury decreased over time. There was no visible injury in soybean with any of the 2,4-D ester treatments at 56 DAE, except for the 2,4-D ester treatment applied at 7 DAP, which caused 1% visible injury at 1155 g ha⁻¹ and 1.3% visible injury at 2310 g ha⁻¹. Soybean generally responded similarly to amitrole and 2,4-D ester when applied at 14 and 7 DPP; however, soybean was more tolerant to amitrole compared to 2,4-D ester when applied at 1 or 7 DAP. The application of amitrole and 2,4-D ester resulted in no biomass or yield reduction in soybean compared to the weed-free, untreated control at all doses and application timings evaluated. Soybean is tolerant to the preplant and pre-emergence application of amitrole or 2,4-D ester at the doses evaluated.     

Effects of temperature on germination and hyphal growth from conidia of Ramularia rhei and Ascochyta rhei, causing spot diseases of rhubarb (Rheum rhaponticum)

Rhubarb leaf and petiole spot disease, caused by Ramularia rhei and Ascochyta rhei , has gradually become more noticeable in the UK field crop. Conidial germination and subsequent colony growth of R. rhei and A. rhei were investigated under in vitro conditions on potato dextrose agar and in vivo on leaf discs. Results indicated that the two fungi responded differently to temperature. Ramularia rhei was better adapted to temperatures ≤ 25°C, with an optimum around 20°C, whereas A. rhei was more adapted to temperatures ≥ 15°C, with an optimum > 25°C. Overall, conidia of R. rhei germinated and subsequent colonies grew at greater rates than those of A. rhei on leaf discs at temperatures ≤ 25°C. These results indicated that it is important to identify the causal agent of leaf and petiole spot diseases in rhubarb field crops in order to estimate disease risks accurately.     

Estimating relative crop yield loss resulting from herbicide damage using crop ground cover or rated stunting, with maize and sethoxydim as a case study

The research goal was to determine whether crop damage from herbicides measured early in the growing season soon after treatment could be used to estimate relative crop yield loss. Percentage stunting was rated visually and percentage crop ground cover (i.e. percentage of the ground surface covered by vegetation) was determined from video photographs taken 2–4 weeks after sethoxydim-susceptible maize ( Zea mays L.) was sprayed with sethoxydim at various rates plus crop oil concentrate. Averaged over 3 years, relative percentage maize yield was a negative sigmoidal function of relative sethoxydim rates from 0.065× to 0.5×, where the 1× rate was 420 g a.i. ha⁻¹ ( r ² = 0.80). Relative maize yield was positively linearly related to percentage crop ground cover and negatively linearly related to rated percentage stunting averaged over 3 years. Linear regression models of relative maize yield vs. percentage maize ground cover explained only slightly more data variability ( r ² = 0.86) than did rated stunting ( r ² = 0.82) over 3 years. The advantages and disadvantages of rated stunting and crop ground cover as scientific measurements are discussed.     

Weed infestation and tea growth under various weed management methods in a young tea (Camellia sinensis[L.] Kuntze) plantation

A field experiment was conducted in the low country of Sri Lanka, during the period 1994–1995 to investigate the severity of weed infestation and tea growth in relation to weed management methods in newly established tea ( Camellia sinensis [L.] Kuntze). Manual weeding (hand and slash weeding) at various intervals was compared with various herbicides, with or without mulching. Weed control with herbicides was superior to that of hand weeding at 6-week intervals or more. Weed control with oxyfluorfen at 0.29 kg ai ha⁻¹ + paraquat at 0.17 kg ai ha⁻¹ or glyphosate at 0.99 kg ai ha⁻¹ + kaolin at 3.42 kg ha⁻¹ were superior. Plots unweeded for 12 weeks or more produced significantly greater ( P  < 0.05) weed biomass than plots unweeded for 6 weeks. Although the least weed dry weight ( P  < 0.05) and the greatest number of weed species were recorded with hand weeding at 2 week intervals, there was no particular benefit on tea growth when compared with hand weeding at 6 and 12 week intervals. Inter row mulching in chemically treated plots was more favorable for tea growth than no mulching, while living weed cover in unmulched slash weeded plots suppressed tea growth. A combination of mulching and herbicides, particularly oxyfluorfen and paraquat, followed by hand weeding at least every 6–8 weeks was considered the most appropriate weed management system for young tea.     

GFP标记的球孢白僵菌在玉米中的定殖

为明确球孢白僵菌在玉米中的定殖分布规律以及不同施用方式和处理浓度对玉米生长发育的影响,本文利用绿色荧光蛋白（GFP）标记的球孢白僵菌,在激光扫描共聚焦显微镜下观测了球孢白僵菌在玉米根部、茎部和叶部的定殖情况,同时检测了不同接种方式在球孢白僵菌不同处理浓度下对玉米生长指标的影响。结果表明,球孢白僵菌在玉米不同组织部位上的定殖有着明显的差异,各球孢白僵菌接种处理中,均以叶部定殖的白僵菌孢子数最多,而茎部均未观测到孢子定殖;玉米根部仅在浸种和灌根处理中可见少量孢子。球孢白僵菌不同接种方式对其在玉米中定殖率的影响差异较大,灌根处理定殖率最高,为76.7%;其次为浸种处理,为73.3%;茎部注射处理及叶面喷施处理定殖率较低,分别为43.3%和36.7%。研究表明,不同施用方式及接种浓度球孢白僵菌孢悬液对玉米生长指标有一定的影响,球孢白僵菌可通过不同接种方式在玉米植株中定殖并扩散,对玉米的生长发育有一定的促进作用,其中以1×10⁶~1×10⁷孢子/mL球孢白僵菌孢悬液浸种或灌根,对玉米苗的促进生长作用最明显。     

Biological control of fusarium crown and root rot of tomato with antagonistic bacteria and integrated control when combined with the fungicide carbendazim

Two bacterial isolates, Bacillus megaterium (c96) and Burkholderia cepacia (c91), demonstrated to be antagonistic against Fusarium oxysporum f.sp. radicis-lycopersici , the causal organism of fusarium crown and root rot of tomato, were evaluated as biocontrol agents alone and when integrated with the fungicide carbendazim. In an initial screening, these isolates reduced disease incidence by 75 and 88%, respectively. In vitro , both biocontrol agents were highly tolerant to the fungicide carbendazim, commonly used to control fusarium diseases. Carbendazim reduced disease symptoms by over 50% when used at > 50  µ g mL⁻¹, but had little effect at lower concentrations. Combination of the bacterial isolates and carbendazim gave significant ( P  ≤ 0·05) control of the disease when plants were artificially inoculated with the pathogen. Application of carbendazim at a low concentration (1  µ g mL⁻¹) in combination with B. cepacia c91 reduced disease symptoms by 46%, compared with a reduction of 20% obtained with the bacterium alone and no control with the chemical treatment alone. A combination of B. megaterium c96 with an increased application rate of 10  µ g mL⁻¹ carbendazim significantly reduced disease symptoms by 84% compared with inoculated controls and by 77% compared with carbendazim treatment alone. In this experiment, the integrated treatment also slightly outperformed application of 100  µ g mL⁻¹ carbendazim, and bacteria applied without fungicide also provided good disease control.     

Effects of wetness period and temperature on development of dark pod spot (Alternaria brassicae) on oilseed rape (Brassica napus)

In controlled environment experiments, when oilseed rape pods or leaves were inoculated with spore suspensions of Alternaria brassicae, the maximum disease incidence (proportion of pods or leaves diseased) increased as wetness period after inoculation increased from 4 to 24 h and as temperature increased to 20°C. There was a clear relationship between disease incidence on pods and incidence on leaves with the same wetness/temperature conditions. Logistic equations described the effects of wetness period after inoculation on disease incidence (number of pods or leaves infected) or disease severity (number of lesions on pods or leaves) using temperature-dependent and tissue-dependent parameters. The time from inoculation to the appearance of the first lesions was shorter on pods than on leaves at temperatures ≤15°C and wetness periods ≤12 h. Two-dimensional response surface equations or simple interpolations from one-dimensional equations were used to develop contour maps of expected disease incidence and severity, respectively, on leaves or pods to estimate the effects of different combinations of wetness period during infection and temperature on disease development.     

Influence of alkyl oleates on efficacy of phenmedipham applied as an acetone:water solution on Galium aparine

Galium aparine plants were treated at the two-whorl stage with technical-grade phenmedipham. The active ingredient was applied at 10 doses as an acetone:water solution, without emulsifier, alone or in mixture with an ester of oleic acid (methyl, butyl, octyl, dodecanyl, octadecanyl). The plant response was described by a log-logistic regression model. Phenmedipham applied alone did not kill the plants even at the highest dose (1621 g a.i. ha⁻¹). In contrast, addition of any alkyl oleate to phenmedipham killed the plants at the 200–400 g a.i. ha⁻¹ doses. The alkyl oleates differently affected activity of phenmedipham. Their effects could be ranked as follows: butyl ≥ methyl; octyl> methyl; dodecanyl ≤ methyl; octadecanyl < methyl oleate. Thus, butyl and octyl oleate promoted phenmedipham activity more than methyl oleate.     

Allelopathy of buckwheat: Assessment of allelopathic potential of extract of aerial parts of buckwheat and identification of fagomine and other related alkaloids as allelochemicals

The allelopathic potential of buckwheat ( Fagopyrum esculentum ) was investigated. Field study showed that living buckwheat reduced weed biomass compared with plots without buckwheat. Laboratory study revealed that root exudates suppressed root and shoot growth of weeds and reduced weed dry weight. Sequential partitioning of the aqueous ethanolic extract of the aerial parts of buckwheat showed that the chloroform extract caused an 80% reduction in radicle elongation of lettuce seedlings at a concentration of less than 100 p.p.m. Fagomine, 4-piperidone and 2-piperidinemethanol were isolated and identified by ¹H and ¹³C nuclear magnetic resonance from the chloroform extract. These compounds caused a 50% inhibition of radicle elongation in lettuce seedlings at concentrations of less than 100 p.p.m. These results suggest that compounds 1, 2, and 3 might act as allelochemicals and affect the growth or germination of different plant species.     

氯虫苯甲酰胺拌种对3种玉米地下害虫的防治效果

为明确氯虫苯甲酰胺种子处理对玉米田地下害虫的防治效果,筛选出合适的田间用药剂量,通过室内盆栽接虫与田间接虫相结合综合评价了氯虫苯甲酰胺对玉米地下害虫沟金针虫、铜绿丽金龟以及小地老虎的综合防治效果。结果表明,盆栽播种后20 d,氯虫苯甲酰胺4 g/kg拌种处理对沟金针虫、铜绿丽金龟和小地老虎的盆栽防效分别为78.15%、80.26%和81.05%;田间播种后20 d,氯虫苯甲酰胺4 g/kg拌种对沟金针虫、铜绿丽金龟和小地老虎的田间接虫防效分别为83.87%、86.27%和88.37%;高剂量的氯虫苯甲酰胺对玉米田地下害虫的田间综合防效优于对照药剂吡虫啉和氟虫腈。氯虫苯甲酰胺拌种处理对玉米种子无不良影响,对出苗和生长有一定的促进作用,有明显的防虫增产作用,可推广应用于防治玉米田地下害虫。