玉米二元覆盖农田水分动态及水分利用效率研究

旱地玉米采用垄面覆膜、垄沟覆不同用量麦草的二元覆盖试验结果表明:随麦草覆盖量的增加土壤保墒效果明显;其中0~100cm土层土壤玉米全生育期累积贮水量5250kg/hm2和9750kg/hm2的麦草覆盖处理比垄面覆膜垄沟未覆麦草处理平均增加146.2mm,水分利用效率提高16.67%~28.65%,降水利用率提高12.39%~18.29%,玉米增产12.10%~18.15%。     

寿光设施菜田碳、氮演变及其对土壤性质的影响

寿光菜田土壤质量衰退的情况日趋严重,直接影响到了蔬菜产业的可持续发展。土壤碳、氮的演变调控着土壤中的物理、化学和生物学过程。为了明确寿光菜田土壤碳氮演变及其对土壤性质的影响,通过野外调查和室内土壤碳氮分析,得出以下结论:与附近粮田相比,寿光菜田的土壤C/N比下降了2.4个单位,有机质增加了4.1 g/kg,全氮增加了0.61 g/kg,土壤全氮的增长量是有机质增长量的2倍。设施菜田土壤NO3--N的显著升高不是菜田土壤C/N比下降的根本原因。菜田土壤碳素输入的量是粮田输入量的1.9倍,设施菜田氮素投入量分别是小麦和玉米的9.9和8.5倍。设施菜田投入的C/N比为4.2:1,粮田的为9.9:1,菜田碳氮投入比例低可能是菜田土壤C/N比下降的重要原因。土壤碳氮含量的增加和C/N比的下降,伴随着菜田土壤明显的酸化和盐渍化,同时也伴随着土壤氮磷钾养分的富集。     

Structure-Activity Relationships (SAR) studies of benzoxazinones, their degradation products and analogues. phytotoxicity on standard target species (STS)

Benzoxazinones 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA) and 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA) have been considered key compounds for understanding allelopathic phenomena in Gramineae crop plants such as corn (Zea mays L.), wheat (Triticum aestivum L.), and rye (Secale cereale L.). The degradation processes in the environment observed for these compounds, in which soil microbes are directly involved, could affect potential allelopathic activity of these plants. We present in this work a complete structure-activity relationships study based on the phytotoxic effects observed for DIMBOA, DIBOA, and their main degradation products, in addition to several synthetic analogues of them. Their effects were evaluated on standard target species (STS), which include Triticum aestivum L. (wheat) and Allium cepa L. (onion) as monocots and Lepidium sativum L. (cress), Lactuca sativa L. (lettuce), and Lycopersicon esculentum Will. (tomato) as dicots. This permitted us to elucidate their ecological role and to propose new herbicide models based on their structures. The best phytotoxicity results were shown by the degradation chemical 2-aminophenoxazin-3-one (APO) and several 2-deoxy derivatives of natural benzoxazinones, including 4-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one (ABOA), 4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIBOA), and 4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIMBOA). They showed high inhibitory activity over almost all species growth. The fact that APO is a degradation product from DIBOA with high phytotoxicity and stability makes it possible to assign an important ecological role regarding plant defense mechanisms. 2-Deoxy derivatives of natural benzoxazinones display a wide range of activities that allow proposing them as new leads for natural herbicide models with a 1,4-benzoxazine skeleton.     

玉米叶片经济和水力性状及其关联性对氮肥和水分的响应

  【目的】  研究叶片经济性状和水力性状的变异性及权衡策略是揭示植物适应环境变化机制和水碳模拟的基础。分析不同氮(N)肥和水分供给下玉米叶片经济性状和水力性状的变异性及相关性,及这些叶片性状与整株植物行为间的关系,以揭示同一物种内不同氮、水有效性下叶片经济性状和叶水力性状间的关系,并探讨叶片性状预测整株生物量和水分利用特征的可能性。  【方法】  采用二因素三水平的盆栽试验,其中氮肥水平包括不施氮肥 (N₀)、播种前施N 0.2 g/kg干土 (N₁)、播种前和五叶期各施N 0.2 g/kg干土 (N₂);水分供应水平包括充分灌水 (W₂)、中度水分胁迫 (W₁) 和重度水分胁迫 (W₀),土壤含水量分别维持在田间持水量的75%～80%、50%～55%和30%～35%约3周,共9个处理。主要测定项目包括叶经济性状 [比叶质量(LMA)、叶厚度(LT)、组织密度(TD)、质量基础上的氮含量(N_mass)和面积基础上的氮含量N_area] 及水力性状 [叶脉密度(VD)、气孔密度(SD)、气孔长度(SL)和最大气孔导度(g_wmax)]。  【结果】  施氮显著增加了LMA、N_mass、N_area、VD、SD、SL和g_wmax (P < 0.05),灌水显著提高了LMA、TD和N_area (P < 0.05);在3种氮水平下,W₂处理的LMA和TD均较W₀处理增加;在N₀和N₁下,W₂处理的SD和g_wmax亦较W₀处理增加,但在N₂下,W₂处理的SD和g_wmax则低于W₀处理,氮、水间的交互作用对LMA、TD、SD和g_wmax的影响达到显著水平 (P < 0.05)。不同氮、水条件下叶经济性状和水力性状间是紧密耦联的,表现在N_mass和SD、g_wmax之间、N_area与g_wmax之间呈显著正相关 (P < 0.05)。影响生物量的主要叶性状为N_area、N_mass和VD,影响耗水量的主要为N_area、N_mass、g_wmax和LT;影响水分利用效率的主要为N_mass、LMA、LT和VD。  【结论】  玉米叶片氮含量与气孔密度、最大气孔导度间存在高度协调性,这种协调性增加了玉米对不同资源有效性的适应性;利用叶片性状可预测不同氮、水供给下玉米的生物量和水分利用特征。     

水分胁迫条件下玉米毛状根再生植株耐旱性研究

以玉米毛状根再生植株为材料探讨其抗旱性,通过形态学指标：株高胁迫指数、干物质胁迫指数、根数、根长、根体积、根干质量、根的总吸收面积、根的活跃吸收面积及根冠比在水分胁迫下的变化的分析、灰色系统分析,表明根干质量、干物质胁迫系数、单株叶面积、根冠比、根体积与抗旱指数关系较密切。研究表明,毛状根再生植株由于强大的根系,即使在水分胁迫下仍能保持良好的根源水分信号,具有较强的抗旱能力。     

灌排调控的稻田排水中氮素浓度变化规律

基于农田排水氮素浓度及湿地进出口断面总氮（TN）、氨态氮（NH4+-N）、硝态氮（NO3--N）浓度的监测,研究了灌溉排水措施以及沟塘湿地对农田排水中氮素浓度变化的影响。结果表明,控制灌溉的水稻全生育期稻田排水中TN、NH4+-N和NO3--N浓度分别较常规灌溉处理低12.08%、20.33%和13.51%;控制排水处理下稻田排水中TN、NH4+-N和NO3--N浓度分别较常规排水处理低2.21%、7.08%和20.92%;湿地出口水体中TN、NH4+-N和NO3--N浓度分别比入口降低了16.8%、14.4%和50.9%,湿地水体中TN、NH4+-N、NO3--N浓度随时间近似服从指数函数衰减趋势。控制灌溉、控制排水及沟渠塘湿地系统的调控措施对农田排水中氮素的净化效果比较显著。     

Determination of triazine and chloroacetanilide herbicides in soils by microwave-assisted extraction (MAE) coupled to gas chromatographic analysis with either GC-NPD or GC-MS

A simple and rapid method based on microwave-assisted extraction (MAE) coupled to gas chromatographic analysis was developed for the analysis of triazine (atrazine, cyanazine, metribuzine, simazine and deethylatrazine, and deisopropylatrazine) and chloroacetanilide (acetochlor, alachlor, and metolachlor) herbicide residues in soils. Soil samples are processed by MAE for 5 min at 80 degrees C in the presence of acetonitrile (20 mL/sample). Mean recovery values of most solutes are >80% in the 10 to 500 microg/kg fortification range with respective RSDs (relative standard deviations) < 20%. The limits of quantification (LOQ) and limits of detection (LOD) are 10 and 1 to 5 microg/kg, respectively. The method was validated with two types of soils containing 1.5 and 3.0% organic matter content, respectively; no statistically significant differences were found between solute recovery values from the two types of soils. The solute mean recovery values from freshly spiked (24 h aging) and spiked samples stored refrigerated for one week before processed were also not statistically different. Residue levels determined in field weathered soils were higher when soils were processed by MAE than with a comparison method based on flask-shaking of soil suspensions overnight. Extracts were analyzed by a gas chromatographic system equipped either with a thermionic (GC-NPD) or a mass spectrometric detector (GC-MS).     

局部供应水氮条件下玉米不同根区的耗水特点

利用分根装置,采用传统均匀灌水、根系分区交替灌水2种方式和作物根区均匀施氮、固定部分根区施氮和根系分区交替施氮3种方式,对零、低、中、高4个施氮水平下玉米根系不同区域的耗水特点进行了研究。结果表明：交替灌水与均匀灌水均表现为,在均匀施氮时玉米两个根区的耗水量随施氮水平的增大一致减小;固定施氮时,随施氮水平的增大,施氮区的耗水量呈明显的减小趋势,从而使两个根区耗水量间的差距增大;交替施氮时的耗水量变化与之相同。而且,两种局部施氮方式下,低氮水平时,玉米两根区间耗水量无显著差异;高氮水平时,未(后)施氮区的耗水量较之先施氮区显著增大,其中尤以固定施氮的增幅更大。与均匀灌水所不同的是,交替灌水缩小了局部施氮条件下不同根区耗水量间的差距。     

Characterization of bacteria isolated from maize roots: Emphasis on Serratia and infestation with corn rootworms (Chrysomelidae: Diabrotica)

Larval corn rootworms (Coleoptera: Chrysomelidae) are soil-dwelling insect pests that damage maize (Zea mays L.) by consuming root tissues, thus lowering grain yield. Little is known about interactions between rootworms and soil bacteria, including potential impacts of maize rhizobacteria, such as entomopathogenic Serratia spp., on subterranean rootworm pests. We used selective growth medium (caprylate-thallous agar, CT) to quantify and isolate Serratia spp. from: (1) bulk soil, (2) roots of four field-grown maize genotypes, half of which were infested with rootworm eggs from a reared colony, and (3) non-diseased, larval rootworms from the same colony. Phenotypic testing and 16S rRNA gene sequencing were used to identify bacteria, including non-Serratia spp., that were successfully isolated on the CT solid medium. We also isolated and identified Serratia spp. associated with non-diseased and diseased Diabrotica adults. Serratia spp. associated with maize roots were more abundant than those associated with bulk soil, where they were undetectable with our methods except for Serratia grimesii. There was no impact of plant genotype on densities of bacteria isolated from maize roots. S. grimesii was frequently associated with maize roots, regardless of infestation with rootworm eggs. Serratia marcescens biotype A4, Serratia plymuthica and several other Enterobacteriaceae genera were also associated with maize roots. Infesting the soil with rootworm eggs enhance the occurrence of two strains of the S. marcescens biotype A1b, with comparable densities of these orange and pink strains within infested roots. However, both strains were associated with larval rootworms from the reared colony, which may indicate that rootworms were introducing these bacteria into infested maize roots. In addition, within larvae the orange strain was significantly more abundant than the pink strain, and was also associated with diseased rootworm adults. Our studies identified specific Serratia strains associated with diseased rootworms that may have potential as biological control agents, and additional Serratia biotypes associated with the maize rhizosphere that, based on the literature, may function as plant growth promoting agents via antagonistic action against plant-pathogenic fungi.     

不同水氮管理下稻田氨挥发损失特征及模拟

为了探讨减少稻田氨挥发的合理水氮管理措施,基于田间试验资料,分析了不同水氮管理稻田氨挥发损失规律及其交互影响,并用DNDC(土壤碳氮循环模型)模型模拟了节水灌溉条件下不同氮肥管理稻田氨挥发损失动态特征。结果表明,控制灌溉和实地氮肥管理的联合应用既大幅降低了稻田氨挥发峰值,又降低了稻田大部分无施肥时段的氨挥发损失,稻田氨挥发损失量为39.63kg/hm2,较常规水肥管理稻田降低44.69%。采用DNDC模型模拟节水灌溉条件下不同氮肥管理稻田氨挥发损失量是可行的,稻季氨挥发总量模拟值与实测值相对误差均在±10%以内。节水灌溉和实地氮肥管理的水氮联合调控显著降低了稻田氨挥发损失量,且实地氮肥管理对氨挥发损失降低的贡献率要大于节水灌溉。该文研究结果可为稻田的水肥科学管理,减少稻田氨挥发损失提供依据。     

Fate of fumonisin B(1) in corn kernel steeping water containing SO(2)

Six 100 ppm fumonisin B(1) (FB(1)) solutions were prepared by dissolving pure standard in six different solvents containing SO(2). Two of the solvents contained 0.2 or 0.4% SO(2) in distilled water. The other four solvents were obtained by steeping corn kernels at 60 degrees C in a 0.2% SO(2) aqueous solution for 6, 12, 24, or 48 h. After the addition of FB(1), all solutions were maintained at 60 degrees C for 7 days. Fumonisin B(1) content in each solution was determined in triplicate by HPLC. Steeping corn kernels in 0.2% solution at 60 degrees C for 6 h seems to be the most effective treatment to decrease the amount of FB(1).     

Factors influencing transformation rates and formation of products of phenylurea herbicides in soil.

Transformation rates of phenylurea herbicides and their products were measured in native soil, sterile soil, soil suspensions, and soil inoculated with pure cultures of microorganisms. In native soil, transformation rates generally increased with decreasing adsorption of the herbicides, but correlations with adsorption coefficients were poor. In sterile soil, substitution patterns of the compounds influenced transformation rates. In soil suspensions, transformation rates increased with lipophilicity of the herbicides. In sterilized soil inoculated with specific microorganisms, transformation was mainly influenced by substrate specificities of the microorganisms to reactive sites of the phenylureas. In all cases, N-demethylation was an important, but not the only, transformation pathway. The data indicate that transformation rates of phenylureas in soils are affected by several parameters, related to the soil, the compounds, and the type of transformation. Although the results were gained in the laboratory under artificial conditions, they form a basis to establish quantitative structure-reactivity relationships and provide explanations for quality and quantity of the formed products.     

土壤磷解吸特性对菜稻轮作田间渗漏水总磷浓度的影响

通过四季豆-瓢瓜-早稻轮作制不同磷肥用量的3年定位田间试验,探讨土壤磷解吸特性及其解吸特征值对菜稻轮作田间渗漏水总磷浓度的影响和评价指标。结果表明,提出的解吸模型可较好地拟合土壤磷素随水土质量比变化的解吸过程,通过该模型能同时得到土壤磷可解吸量Q、土壤溶液磷浓度Cli及其缓冲系数b等解吸特征值。菜菜稻轮作的总磷浓度平均只有菜菜连作的42.6%。土壤磷可解吸量与田间渗漏水总磷浓度之间满足双速率转折点的动态特征。无论是菜菜连作还是菜菜稻轮作,Q值表征的土壤磷素淋失转折点的差异很小,平均为24.4 mg kg-1。因此,菜菜稻轮作有利于削减田间渗漏水总磷浓度,土壤磷可解吸量的双速率转折点X0可用于表征菜田磷素淋失潜力的指标之一。     

Structure-activity relationship (SAR) studies of benzoxazinones, their degradation products, and analogues. Phytotoxicity on problematic weeds Avena fatua L. and Lolium rigidum Gaud

Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass) are highly problematic weeds affecting a wide variety of cereal crops worldwide. The fact that both of these weeds have developed resistance to several herbicide groups made them optimal candidates as target organisms for ongoing research about the potential application of allelochemicals and analogue compounds as natural herbicide models. Benzoxazinones, a family of natural allelochemicals present in corn, wheat, and rye, including 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, together with some degradation products, found in crop soils as well as in other systems, and some synthetic analogues of them were tested on wild oat and rigid ryegrass seeds; the results were statistically treated, and some structure-activity relationships, useful in further development of natural herbicide models, were elucidated. The most active compounds were the synthetic benzoxazinone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazin-3-one, with highly significant inhibition on the development of both weeds. The ecological role of these compounds is discussed by considering both degradability and phytotoxicity. The bioactivity of aminophenoxazines has been correlated by their aqueous solubility-lipophilicity predicted by means of computational methods.     

Second derivative spectrophotometric determination of acetaminophen and phenacetin in presence of their degradation products

A rapid and accurate method for determining acetaminophen and phenacetin in presence of their degradation products is presented. Solutions of these drugs in 0.1N HCl were analyzed by measuring their second derivative spectral response at 295 nm where the degradation products do not interfere. The mean percent recoveries for mixtures of acetaminophen and/or phenacetin with the corresponding degradation products were 100.2 +/- 0.6 and 100.6 +/- 1.1, respectively. The method can be used for assessing the stability of the 2 drugs. The proposed method is also applied to the determination of acetaminophen in tablets and syrups.     

Role of maize hybrids and their chemical composition in Fusarium infection and fumonisin production

This study was designed to investigate the role of hybrids in maize Fusarium section Liseola interaction and fumonisin production, with particular emphasis on the occurrence and accumulation of hidden fumonisins in maize (masking phenomenon). In this 2 year study, naturally infected field crops were chosen with 10 maize hybrids, six of them grown in both years. Maize samples collected in 2010 showed a higher incidence of fungal infection as well as higher fumonisin contamination than those obtained in 2009 but a very similar incidence of F. section Liseola. Fumonisin masking was confirmed in raw maize, with a lower amount of hidden forms as compared to free fumonisins detected in the year with higher contamination. The chemical composition of the different hybrids was determined and correlated with the contamination data: the results obtained highlight the main role of fatty acids, with a higher fumonisin contamination in hybrids showing a higher linoleic acid content and a higher masking action in hybrids with higher oleic to linoleic ratio. These results represent a good basis to explain maize hybrid susceptibility to F. section Liseola infection, fumonisin contamination, and masking not related to a specific commercial hybrid but extendable to all hybrids.