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1.
为探明生防菌Br-2在分枝列当体内及番茄根围的定殖能力,采用PEG-CaCl_2介导的原生质体转化体系将红色荧光蛋白基因DsRed转入到菌株Br-2中,并构建其生长曲线,测定其对分枝列当种子萌发的抑制率,通过共聚焦显微镜观察其在分枝列当茎内及番茄根围的定殖情况。结果表明:通过原生质体转化体系得到了标记菌株Br-2-DsRed,继代培养5代后,其在共聚焦显微镜下仍可观察到亮红色荧光,经PCR检测带有DsRed基因,证明其稳定性好。标记菌株Br-2-DsRed与野生菌株Br-2的生长曲线基本一致,对分枝列当种子萌发的抑制率分别为75.86%和74.14%,无显著差异。显微观察发现,标记菌株Br-2-DsRed接种1 d后即能够侵染分枝列当的茎部表皮,3 d后主要分布在茎表皮和厚壁细胞间隙,5 d后侵染到厚壁细胞及维管束细胞内部并导致茎部腐烂;而标记菌株Br-2-DsRed不能侵染番茄根尖的内部,主要定殖在番茄根尖表面。  相似文献   

2.
Broomrapes (Orobanche spp.) are parasitic weeds that cause significant losses of crop yield. Experiments were conducted to investigate the seed response to the artificial germination stimulant GR24 in three species of Orobanche subjected to preconditioning under various temperatures, water potentials and with plant growth regulators. The highest germination percentages were observed in Orobanche ramosa, Orobanche aegyptiaca and Orobanche minor seeds conditioned at 18°C for 7 days followed by germination stimulation at 18°C. With the increase of the conditioning period (7, 14, 21 and 28 days), the germination percentage of O. ramosa and O. aegyptiaca progressively decreased. When conditioned at −2 MPa, the germination percentage was lower than at 0 and −1 MPa, especially at 13 and 28°C. Orobanche minor seeds could retain relatively high germination if conditioned at 18, 23 or 28°C, even after significantly extended conditioning periods (up to 84 days). GA3 (30–100 mg L−1), norflurazon and fluridone (10–100 mg L−1), and brassinolide (0.5–1.0 mg L−1) increased seed germination, while 0.01 mg L−1 uniconazole significantly reduced germination rates of all three Orobanche spp. The promotional effects of GA3 and norflurazon and the inhibitory effect of uniconazole were evident, even when they were treated for 3 days. Germination of Orobanche seeds was much lower when the unconditioned seeds were directly exposed to GR24 at 10−6 m . This early GR24-induced inhibition was however alleviated or even eliminated by the inclusion of GA3 or norflurazon (10–50 mg L−1) in the conditioning medium. On the contrary, the inclusion of uniconazole increased the inhibitory effect of GR24, particularly in the case of O. ramosa.  相似文献   

3.
Adsorption, incubation and soil-column experiments with bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were carried out in ten different soils from the marches surrounding the Doñana National Park (Huelva, SW Spain). Adsorption isotherms for the different soils showed a good fit with the Freundlich equation. Bentazone was poorly adsorbed in all the soils studied, with no significant relationship between theKf values and soil characteristics. A significant correlation was obtained between the soil organic matter content and the distribution constant values (Kd) calculated at an equilibrium concentration of 200 μg cm−3. The low adsorption and non-degradation of bentazone on these soils suggest that the herbicide readily percolates through soils to reach the surface and ground waters. The mobility of bentazone through three soil columns was also studied. The mass balances carried out showed that bentazone was totally eluted from the soil columns. The theoretical model applied to explain bentazone leaching under our experimental conditions seems to be suitable for soil columns with a uniform water-flow rate.  相似文献   

4.
The activity of GR7 and Striga germination stimulant(s) from Euphorbia aegyptiaca Boiss. showed adequate persistence (6–8 days) in acidic soils (pH 5·0–6·3), but residual activity was short (1–3 days) in alkaline soils. The compounds tended to lose activity at a faster rate in the alkaline clay Gezira soil (pH 7·8), than in its sandy equivalent (pH 8·1). In solution, pH had no influence on initial activity, but residual action was reduced more rapidly by alkalinity and high temperature. However, the rate of loss of activity in solution was slower than in soils.  相似文献   

5.
为明确埃及吹绵蚧Icerya aegyptiaca昆虫病原真菌在生物防治中的应用潜力,采用生物测定法筛选得到产孢量高和致病力强的优势分离株,根据形态学特征和rDNA ITS序列分析对优势分离株进行鉴定,并对其室内毒力和温室防效进行测定。结果显示,筛选得到的优势分离株为IJID003,产孢量最高,可达8.51×10~6个/mL,且致病力最强,处理埃及吹绵蚧2龄若虫5 d后,其校正死亡率为95.40%;根据形态学特征和r DNA ITS序列分析鉴定结果,确定该分离株为爪哇棒束孢Isaria javan‐ica。随着分离株IJID003接种浓度的增加,埃及吹绵蚧2龄若虫、3龄若虫和雌成虫的校正死亡率也随之增加,致死中时间LT50则递减;在分生孢子浓度为1.00×10~8个/mL时,其对2龄若虫、3龄若虫和雌成虫的LT50最小,分别为1.89、2.29、2.31 d;随着接种后天数的延长,致死中浓度LC50减小,在接种后6 d,其对2龄若虫、3龄若虫和雌成虫的LC50最小,分别为1.25×10~3、2.04×10~4、8.37×10~5个/mL,表明分离株IJID003对埃及吹绵蚧2龄若虫的毒力较其它2种虫态高;啶虫·毒死蜱2 000倍液对埃及吹绵蚧2龄若虫的前期致死速率较快,而分离株IJID003在后期侵染速率较快,处理后6 d两者的防效无显著差异,效果相当。表明爪哇棒束孢分离株IJID003具有产孢量高且致病力强的特点,在埃及吹绵蚧生物防治中具有较好的应用前景。  相似文献   

6.
Several laboratory and glasshouse experiments were conducted to assess seed germination, seedling establishment and growth patterns of wrinklegrass (Ischaemum rugosum Salisb.) influenced by temperature and light regimes, and chemical media. Wrinklegrass was a positively photoblastic species, and seed germination was temperature‐dependent and light‐mediated. Seeds soaked in distilled water for 24 h, or oven‐dried at the respective temperature regimes of 15, 20, 25, 30, 35, or 40°C prior to treatment in distilled water and incubated in darkness, failed to germinate. Likewise, no germination prevailed when the seeds were exposed to similar temperature regimes and treated with 0.2 m KNO3, 5% H2O2 or 0.01 m HNO3, and incubated under continuous darkness. Seeds treated with 5% H2O2 at 30°C, or oven‐dried and treated with 0.01% M HNO3 at 35°C registered 10 and 20% germination. Approximately 75 and 90% of the light‐exposed seeds for all treatments germinated in the first three and six days at 25°C. No germination occurred at 15°C in the first three days after treatment. Seeds subjected to 40°C for six days after treatment recorded 36% germination. The optimum temperatures for seed germination were 25–30°C. Seed drying and soaking treatments widened the windows of the optimal temperatures for wrinklegrass germination. The acidic media of KNO3, H2O2 or HNO3 favored seed germination. Less than 5% of seed germination occurred with burial or water inundation at depths exceeding 2 cm. Seed burial or inundation at ≥2 cm depths inhibited seed germination. Seeds sown onto moist paddy soils registered ca. 50% germination. Free‐floating seeds on the water surface registered ca. 98% germination within the first six days after seeding. The mean number of seedlings that survived was inversely proportional to water depths, with close to 100% mortality at the 14 cm depths of inundation. Both plant height and seedling survival were linearly proportional to the amount of root mass of seedlings which penetrated the soil. The weed was a prolific seed producer (ca. 6000 seeds/genet or 18 000 seeds/genet per year). The vegetative and reproductive efforts of each wrinklegrass plant registered values of 0.68 and 0.32, respectively.  相似文献   

7.
水分对不同栽培年限日光温室土壤氮矿化的影响   总被引：1，自引：0，他引：1  
采用室内短期（84 d）好气培养法评价了不同水分供应水平下（田间持水量的60%、80%及100%,分别用60FC、80FC和100FC表示）陕西杨凌地区不同栽培年限（种植前、种植第二年及种植第三年）日光温室土壤（0~20 cm及20~40 cm土层）氮素矿化特性。结果表明：随着日光温室栽培年限的延长,0~20 cm土层累积净矿化氮量显著增加,且随栽培年限的增加,20~40 cm 土层氮矿化势呈增加的趋势;土壤水分含量由60FC增加到80FC,土壤累积矿化氮量呈增加趋势,但当含水量达到100FC时,土壤累积矿化氮量降低。回归分析结果表明,土壤有机质含量每增加1 g·kg-1, 60FC、80FC、100FC土壤含水量条件下土壤氮矿化势分别增加 1.62、1.88 mg·kg-1和1.57 mg·kg-1;土壤全氮含量每增加1 g·kg-1,土壤氮矿化势分别增加28.93、33.42 mg·kg-1和27.82 mg·kg-1。因此,建议日光温室蔬菜栽培中应综合考虑温室年限及灌溉量对土壤氮素矿化过程的影响。  相似文献   

8.
Highest inorganic bromine residues (30 ppm) were found when soil was fumigated with liquid methyl bromide (MB) introduced by conventional means into evaporating dishes. With preheated (vaporized) MB or injection of MB/chloropicrin (CP) mixtures, bromide concentrations were reduced by 50%. They were uniform throughout the soil (0 to 60 cm) except after MB/CP injection, when larger residues were found in the 30-60 cm layer. Leaching with 2000 mp3/ha (20 cm) of water always reduced bromide content to 7.5 and 10 ppm at the 0-30 and 30-60 cm depth, respectively. Organic amendments to soils substantially increased bromide levels up to 118 ppm, most of which was found in the upper soil layers; two teachings with 2000 mp3 /ha water were required to return the soils to their normal state.Sclerotium rolfsii andFusarium oxysporum f. sp.dianthi cultures buried in soil were eliminated from the upper 30 cm with MB applied either conventionally or preheated. At 50 cm, 500 kg/ha of the preheated gas was superior to 1000 kg/ha of the cold gas. All MB fumigations suppressed carnation flower yields compared with CP alone but were superior to no treatment. After leaching, MB-fumigated soils yielded the highest number of flowers.  相似文献   

9.
Residual effects of chlorotriazine herbicides in soil at three Rumanian sites. II. Prediction of the phytotoxicity of atrazine residues to following crops Total and plant-available atrazine residues in the top 10 cm soil were measured 120 days after application of 3 kg ai ha?1 to maize (Zea mays L.) at three sites in Rumania. At one site, similar measurements were made 3?5 years after application of 100 kg ai ha?1. Plant-available atrazine residues were estimated by extraction of soil samples with water, and by bioassay using Brassica rapa as the test plant. It was calculated that between 30 and 120μg atrazine 1?1 was potentially available to plants in the different soils. Dose-response relationships for atrazine and the most important rotational crops with maize in Rumania—sunflower, winter wheat, soybean and flax—were determined in hydroponic culture using herbicide concentrations corresponding with the plant-available fractions measured in the different soils. ED50 values were determined by probit analysis and the results showed that sunflower (ED50, 22μg 1?1) was the most sensitive crop, and soybean (ED50, 78μg 1?1) was the least. The residual phytotoxicity of atrazine to succeeding crops in the different soils was predicted using the appropriate availability and phytotoxicity data, and the results showed good agreement with those observed. The results suggest that measurements of plant-available herbicide residues afford a rapid method of assessing possible phytotoxicity to following crops.  相似文献   

10.
The distribution resulting from the drenching of soil with a suspension concentrate of [14C]metazoxolon was studied in the laboratory and the field. Penetration of soil columns was increased by (a) increasing the drench volume from 1 to 7.8 litres m?2, (b) changing the original soil moisture content from air-dry to field-capacity, and (c) including 1 % of ‘Renex 30’ surfactant in the drench. Penetration was greatest in soils containing large pores and was reduced when aggregates were broken down by sieving. Leaching the column with 1.56 cm of ‘rain’, 15 h after treatment, did not increase the penetration by metazoxolon. In all experiments, the maximum concentration of metazoxolon occurred in the top 2 cm of soil. Equivalent effects were found when metazoxolon was applied to a poorly-structured sandy clay loam in the field.  相似文献   

11.
Soil available water capacity (AWC) is an important factor affecting soil productivity in semiarid and subhumid environments and is mainly determined by the soil textural composition. As the soils of these environments usually present fairly uniform textures across depth, we hypothesized that it would be possible to accurately estimate the whole-profile AWC using surface information. Our objective was to test this hypothesis in the Argentine Semiarid Pampas. Information was collected from 152 sites where AWC was measured in 20?cm layers up to a depth of 140?cm or up to the upper limit of the petrocalcic horizon, when present. In each case, whole profile AWC was estimated using a one-step and a two-step approach, comparing multiple regression and artificial neural networks as modeling techniques. Both modeling methods were effective (R2?>?0.76, P?相似文献   

12.
为合理评估除草剂异唑草酮的环境风险,在实验室模拟条件下,研究了异唑草酮在土壤 (红壤土)表面光解以及在不同质地土壤 (潮土、水稻土和红壤土) 中的降解和淋溶特性。结果表明:异唑草酮在土壤表面的光解遵循一级反应动力学方程ct = 4.23e–0.008t (r = 0.937),半衰期为82.5 h;其在潮土、水稻土和红壤土中的降解均符合一级动力学方程,好氧条件下,异唑草酮在3种土壤中的降解半衰期分别为10.5、43.3和139 h,厌氧条件下的降解半衰期分别为19.4、18.4和158 h;其在潮土、水稻土和红壤土中的淋溶系数 (Rf) 分别为0.417 0、0.083 3和0.083 3。研究表明:异唑草酮在土壤表面光解速率较慢,而在土壤中好氧及厌氧条件下降解速率均较快,残留期短;其在土壤中淋溶性较弱,不易对周围环境及地下水造成污染风险。  相似文献   

13.
为明确臭氧对韭菜迟眼蕈蚊Bradysia odoriphaga的毒力及对韭菜和土壤环境安全性的影响采用室内生测法测定了臭氧对3龄幼虫、蛹和成虫的毒力,并测定了臭氧水对韭菜种子的影响及对土壤环境的安全性。结果显示,臭氧对韭菜迟眼蕈蚊3龄幼虫和蛹均有较高的毒力,LC_(50)分别为3.79 mg/L和4.95 mg/L;对其成虫的毒力稍弱,LC_(50)为61.52 mg/m~3。臭氧水浓度为4.50 mg/L时对韭菜种子萌发和幼苗生长促进效果最显著,发芽率、根长和芽长较对照分别显著增加了22.29%、14.11%和4.75%。4.50 mg/L臭氧水处理土壤后,细菌、真菌和放线菌数量较对照分别显著下降了91.91%、85.71%和59.99%;土壤pH提高了2.07%,速效钾含量显著上升了313.19%,有效磷、氨态氮、有机质的含量分别下降了4.69%、18.75%、35.44%。表明臭氧对韭菜迟眼蕈蚊3种虫态均有杀伤作用,且对韭菜种子萌发和幼苗生长有良好的安全性,但对土壤环境有一定影响。  相似文献   

14.
The objective of this study was to investigate the potential of native Thai species for reclaiming salt-affected areas in Thailand. Plant species diversity in Nakhon Ratchasima Province in northeast Thailand, and their soil characteristics (texture, electrical conductivity (ECe), exchangeable sodium percentage (ESP), and pH) were measured. A total of 19 species in 16 genera of 12 families were found, among which the most abundant species belonged to the Poaceae and Cyperaceae families. The highest values of ECe were found near the surface (0–20?cm) with an average range between 30–80?dS?m?1, while lower values in the range of 15–25?dS?m?1 were found at lower depths (20–100?cm). Soil conditions in the subplots with plant coverage showed lower ECe and ESP when compared to plots without vegetation. Seeds from the three most frequently occurring species, including Azima sarmentosa, Gymnosporia mekongensis, and Buchanania siamensis, were then tested for germination at different salinities. Seeds of all three species germinated at high salinities, from 25–45?dS?m?1, with total germination ranging 40–90%. Together with the ability to germinate at high salinities, these native species showed deep, rapid root elongation, likely to escape high surface ECe levels (approximately the top 30?cm). Planting these species in areas with vegetation coverage would aid successful reclamation of saline areas. Reclaiming salt-affected soils will not only improve local farmer’s economic status, but can also reduce the extent of deforestation, benefiting the entire ecosystem.  相似文献   

15.
威百亩对西葫芦常见土传病原菌的毒力及田间防效   总被引：2，自引：1，他引：1  
为明确威百亩对西葫芦常见土传病原菌的活性及田间防治效果,以1,3-二氯丙烯为对照药剂,采用改进的密封盘法比较了2种熏蒸剂对西葫芦菌核病菌等4种病原菌的毒力及对菌核萌发的影响,并于田间采用密闭熏蒸法比较了2种药剂对西葫芦茎基腐病的防治效果.室内结果显示:威百亩对西葫芦菌核病菌、茎基腐病菌、枯萎病菌及绵腐病菌的EC50分别为0.060、0.945、1.380、2.953 mg/L,而1,3-二氯丙烯对这4种病原菌的EC50为516.654、928.558、633.784、77.242 mg/L,威百亩0.228 mg/L可完全抑制菌核的萌发.田间药效试验表明:威百亩150、90、75、60 kg/hm2及1,3-二氯丙烯200 kg/hm2均能不同程度控制西葫芦茎基腐病的发生,防治效果分别为88.94%、87.58%、83.76%、80.60%和64.80%,且各试验剂量均对西葫芦安全并能在一定程度上起到增产作用,威百亩150 kg/hm2处理增产率最高,达34.82%.从防治效果及经济效益分析,在西葫芦田推荐使用威百亩防治土传病害.  相似文献   

16.
Aqueous extracts of fifteen Euphorbia species induced germination of Striga hermonthica (Del.) Benth. seeds to varying extents. Extracts from E. supina Raf., E. pilulifera Jacq., E. acalyphoides Hochst. ex. Boiss, E. prunifolia (Jacq.) Hort. Schoent., E. hirta L., E. aegyptiaca Boiss, E. splendens Boj., and E. granulata Forsk, were the most active. Extracts from E. acalyphoides and E. pilulifera were inhibitory at high concentrations. Undiluted extracts from E. pilulifera, E. aegyptiaca and E. hirta induced haustorial initiation. The stimulatory substance(s) were widely distributed in plants of E. aegyptiaca. Extracts from E. aegyptiaca also stimulated seed germination and haustorial initiation in a range of Striga species and strains.  相似文献   

17.
The phytopathogenic fungi Fusarium oxysporum f. sp. lycopersici and Rhizoctonia solani were completely eradicated after exposure for 30 min to a 0.4-0.5 % aqueous solution by weight of formaldehyde. With metham-sodium, higher concentrations or longer exposures were needed to obtain similar results. When tested in tuff (a granular plant growth medium of volcanic rock origin), the toxicity of formaldehyde was lower and that of metham-sodium was higher, compared with the corresponding toxicities in aqueous solutions. Both fungicides eradicated the two fungi, as well as Pythium myriotilum, when tested under practical conditions in vertical aluminium tubes filled with tuff. No detrimental effect could be observed on strawberry plants subsequently grown in these columns.  相似文献   

18.
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19.
Field bioassays were conducted to assess the toxicity of three insecticides, chlorpyrifos, cypermethrin and pirimicarb, to four species of springtails, Isotoma viridis, Isotomurus palustris, Folsomia candida (Collembola: Isotomidae) and Sminthurus viridis (Collembola: Sminthuridae). Spray residues on two soil types (a sandy clay loam and a sandy soil) were obtained in the field, in the presence and absence of a wheat crop canopy, after spray application by a commercial tractor-mounted sprayer. Collembola were then confined for 24-h periods on the sprayed soils in a constant laboratory environment at 1, 2, 3, 8 and 15 days after treatment. Residual insecticide toxicity was compared between species, insecticides, soils and exposure conditions (crop or no crop) using the age of residue at which median mortality occurred (DAT50). Cypermethrin and pirimicarb residues were of low toxicity, causing less than 10% mortality, whereas residues of chloryprifos were toxic to all four species of Collembola on both soil types and in both exposure treatments. Interspecific differences in collembolan susceptibility to chlorpyrifos residues gave the ranking (from most to least susceptible) S. viridis>F. candida>Isotomurus palustris>Isotoma viridis. Residues on the sandy soil were more toxic than those on the sandy clay loam. These results are discussed in terms of how field bioassay approaches may be used to determine pesticide residual toxicity to microarthropods. We conclude that field bioassays offer a feasible method for evaluating the toxicity of pesticides and the persistence of toxic effects on Collembola. Advantages and disadvantages of this method are considered.  相似文献   

20.
In field trials, loamy soils were fumigated by injecting dichloropropene and metham-sodium with a horizontal-blade injector. Concentrations of cis- and trans-1,3-dichloropropene, and of methyl isothiocyanate were measured. The influence of different methods of tillage on fumigation effectiveness was compared by computing concentration-time products at the various depths in the soil. With a fine-structured top layer, there was no clear beneficial effect of shallow or deep rotary tillage before injection. If a dense top layer was not rotary-tilled beforehand, deep and wide cracks were formed during injection. Shallow or deep rotary tillage both left loose cereal stubble mixed in the surface layer, which was difficult to finish off. Concentration-time products could be substantially increased by finishing off the soil surface better after injection.  相似文献   

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