膜下滴灌水氮对棉花根系形态和生物量分配变化的影响

通过挖掘法,研究了膜下滴灌不同生育期棉花根系形态特征和生物量分配对不同水氮的响应。结果表明:花铃期,正常灌水促进了根系和地上部的生长,根、地上部干重、根表面积指数、平均根长密度显著增加,根冠比下降。无论灌水量如何,施氮促进了根系和地上部的生长,但对地上部的促进作用远大于根系,表现为根冠比下降。吐絮期,在低氮条件下,灌水量增加,根干重、地上部干重显著增加。在中氮和高氮条件下,不同的灌水量对根干重没有影响。无论施氮量如何,灌水量增加,平均根长密度、根表面积指数显著下降,地上部干重明显增加,根冠比下降。水分胁迫时,中氮的根干重明显高于低氮和高氮处理,而施氮对地上部干重,平均根长密度的影响不明显,根表面积有降低的趋势。正常灌水时,施氮量增加,根干重、根长密度、根表面积指数显著降低,地上部干重以中氮水平最高。花铃期至吐絮期,根干重随生育期的延长明显增加。水分胁迫条件下,平均根长密度、根表面积指数随生育期的延长有增加的趋势。正常灌水条件下,平均根长密度、根表面积指数随生育期的延长下降。     

微纳米气泡水地下滴灌对紫花苜蓿土壤酶活性与根系脯氨酸的影响

为了探究微纳米气泡水地下滴灌条件下不同溶解氧质量浓度对紫花苜蓿土壤酶活性与根系脯氨酸的影响，采用田间试验方法，在地下滴灌灌溉定额相同的条件下设低（WA-1,1.8 mg·L^-1）、中（WA-2,5.0 mg·L^-1）、高（WA-3,8.2 mg·L^-1）3个微纳米气泡水溶氧量质量浓度水平和不加气常规灌溉处理（CK），研究了不同试验处理下紫花苜蓿根际土壤过氧化氢酶、脲酶活性以及根系特征和游离脯氨酸含量的变化。结果表明：微纳米气泡水地下滴灌能明显增加紫花苜蓿根区土壤过氧化氢酶和脲酶活性；在紫花苜蓿不同的生长期，随着微纳米气泡水溶解氧质量浓度的增加，土壤过氧化氢酶和脲酶活性呈增大的趋势；相同试验处理条件下，土壤过氧化氢酶和脲酶活性随着微纳米气泡水地下滴灌次数的增加呈先升后降的趋势；处理WA-3、WA-2、WA-1的土壤过氧化氢酶活性和脲酶活性最大分别为20.28、19.19、16.92 ml·g^-1和13.98、13.17、12.07 mg·g^-1·d^-1，分别比处理CK（13.82 ml·g^-1和9.63 mg·g^-1·d^-1）增加46.74%、38.86%、22.43%和45.17%、36.76%和25.34%；微纳米气泡水地下滴灌能降低根系游离脯氨酸含量，处理WA-2根系游离脯氨酸含量最低（51.01μmol·g^-1），相较于处理CK(92 μmol·g^-1)，减少44.55%。说明微纳米气泡水地下滴灌能够缓解因长时间地下滴灌导致的土壤通透性减弱的现象，提高土壤氧气扩散率，增强土壤酶活性，促进根系的正常生长发育。     

局部高浓度硝酸盐供应对玉米根系 形态及氮累积的影响

以郑单958和鲁单981为研究对象，进行水培分根试验，在正常供水和水分胁迫条件下，分别以均匀低浓度硝酸盐处理主根和种子根(LPR-LSR)、局部高浓度硝酸盐处理主根（HPR-LSR）和局部高浓度硝酸盐处理种子根（LPR-HSR），测定分析根系形态、生物量以及氮含量。结果表明：与氮低效鲁单981相比，氮高效郑单958具有较高的主根根长、根表面积、根系生物量、地上部生物量和氮累积量。水分胁迫条件下，郑单958和鲁单981的主根的根长、根表面积、根体积、地上部生物量和氮累积量总体上均低于正常水分条件。玉米主根和种子根对局部高浓度硝酸盐的反应存在差异。与均匀低浓度硝酸盐处理相比，局部高浓度硝酸盐处理促进正常水分条件下主根和种子根根系的生长，尤其是根长和根系表面积；在正常水分条件下，主根根长和根系表面积增加幅度范围为6.8%~27.3%和1.9%~21.9%，除HPR-LSR处理条件下的郑单958外，种子根根长和根系表面积增加幅度范围为30.4%~92.7%和10.5%~135.1%；在水分胁迫条件下，主根根长和表面积增加幅度范围为24.6%~152.9%和62.1%~229.9%，然而种子根根长降低了10.0%~29.9%，表明水分胁迫会影响种子根对高浓度硝酸盐的响应。除水分胁迫条件下LPR-HSR处理外，局部高浓度处理可同时增加两侧根系的生物量和氮累积量。无论是正常供水还是水分胁迫，与LPR-LSR处理相比，局部高浓度硝酸盐供应均能够增加地上部生物量以及氮累积量，在LPR-HSR处理条件下，增加幅度范围分别在35.0% ~107.9%和162.9%~291.1%，在HPR-LSR处理条件下分别为56.7%~109.4%和204.1%~377.0%，HPR-LSR处理条件下增加幅度较大，表明在氮素非均匀分布环境中，当主根处于高浓度硝酸盐区域时将会更显著促进生物量的增加和氮累积。     

水分胁迫对线辣椒根系生长及产量的影响

以陕西省关中线辣椒产区普遍种植的两个线辣椒品种多娇和辛香8号为试材,研究水分胁迫对其根系形态发育及产量的影响。试验采用盆栽方法,设置5个水分梯度：40%～50%（T1）,50%～60%(T2),60%～70%(T3),70%～80%(T4),80%～90%（CK）,测定其单株总根长、根体积、根表面积、根尖数、根交叉数、根分叉数、根平均直径、根冠比、 单株结果数和单株产量等。结果表明,各处理的单株总根长、根体积、根表面积、根尖数、根交叉数、根分叉数在水分胁迫的第20～40天期间,增加速率明显减小,甚至出现负增长,说明此时期是线辣椒根系对水分胁迫最敏感的时期;不同处理之间单株总根长、根体积、根表面积、根尖数、根分叉数、根交叉数表现为CK＞T4＞T3＞T2＞T1,T1、T2在整个水分胁迫期间均显著地抑制了根系的生长,T3、T4主要在第20～40天期间显著抑制了根系生长;在整个胁迫期间,各处理的根冠比和根平均直径均大于对照,说明线辣椒在水分胁迫下,其根系吸收的水分会首先用于保证根系自身生长,且胁迫处理不利于细根的生长及侧根的发生;单株结果数和单株产量随着土壤水分含量的降低而减少;辛香8号在各胁迫处理下的根系生长受抑制程度及单株减产程度均大于多娇,说明辛香8号的耐旱性弱于多娇。     

外源水杨酸对连作马铃薯生长发育及抗性生理的影响

探讨了不同浓度外源水杨酸处理对连作马铃薯幼苗生长发育、耐连作障碍、抗氧化能力以及块茎营养的影响。结果表明：5年连作导致马铃薯幼苗叶片中叶绿素含量、净光合速率、细胞膜稳定指数、渗透调节物质含量、抗氧化剂含量、抗氧化酶活性显著下降,块茎产量和硬度降低,块茎淀粉、Vc、可溶性蛋白含量下降,叶片MDA含量、活性氧水平显著增加,植株生长发育受到显著抑制;在施用外源水杨酸处理后,马铃薯幼苗的相对含水量增高,叶绿素含量、净光合速率、 根系活力和细胞膜稳定指数增强,生长得到促进,植物叶片内渗透调节物质含量、抗氧化剂含量、抗氧化酶活性提高,块茎产量、硬度以及块茎淀粉、Vc、可溶性蛋白含量增高,叶片MDA含量、活性氧水平显著降低;比较不同浓度的外源水杨酸处理,以20 μmol·L^-1和30 μmol·L^-1对促进马铃薯连作幼苗生长发育及缓解连作伤害效果最佳,其中对于连作5年的马铃薯,30 μmol·L^-1外源水杨酸处理相比于对照块茎产量相对增加64.4%,而叶片净光合速率相对增加287.0%。可见,适宜浓度的外源水杨酸处理显著减轻了连作障碍造成的伤害,促进了马铃薯植株的生长发育,提高了马铃薯块茎的产量,并改善了块茎的营养与品质。     

减氮增密对西南丘陵区旱地直播油菜根系发育及水分利用的影响

以氮肥施用量N1(108 kg·hm~(-2))、N2(144 kg·hm~(-2))、N3(180 kg·hm~(-2))及种植密度D1(15×10~4株·hm~(-2))、D2(22.5×10~4株·hm~(-2))、D3(30×10~4株·hm~(-2))、D4(37.5×10~4株·hm~(-2))设置12个处理,以当地传统种植方式(N3D1)为对照,在生态脆弱、水土流失严重的西南丘陵区研究了油菜不同生育期根冠比(R/T)、根系形态、土壤蓄水量以及经济产量、水分利用效率、经济收益对不同氮肥施用量及种植密度的响应。结果表明:施氮量极显著影响油菜蕾薹期、角果期及成熟期的R/T与角果期的总根长和根系总表面积,同时显著影响蕾薹期的总根长和根系总体积;种植密度极显著影响蕾薹期R/T及角果期根系总体积,同时显著影响蕾薹期的根系总表面积和根系总根体积。角果期为地上部生物量积累速率最大时期,根冠比相较蕾薹期减小55.5%,而苗期的根冠比与经济产量呈显著负相关(r=-0.673~*)。氮肥减施可以有效增加土壤蓄水量和生育期总耗水量,且氮肥减施40%后更为显著,前者表现为N1N2N3,后者则为N3N2N1;相较N3,N1和N2下的各处理平均总耗水量分别减少5.03%和3.24%。在N2下,经济产量和水分利用效率则随着种植密度的增加而显著增加;经济收益与水分经济收益也表现出显著增长的变化趋势,其中,N2D3、N2D4处理较对照每公顷经济收益增加290.73元和503.37元,水分经济收益提高2.72%和9.93%。N2D3或N2D4处理能促进油菜产量、土壤蓄水量及经济收益的增长,并显著提升水分利用效率及水分经济收益,可作为西南丘陵区直播油菜减肥增效优化种植方式。     

杂草稻与栽培稻苗期根系形态和生理特性比较

杂草稻较强的抗逆性以及对栽培稻的竞争优势与杂草稻的较快生长速率、较强光能利用率等地上部分生物学特性密切相关,但其根系形态及生理特性对其竞争力和抗逆性的影响鲜有报道。本试验以5个不同地区杂草稻种群为材料,以栽培稻(日本晴)为对照,测定播种后10、20、30 d杂草稻和栽培稻根系形态(总根长、根表面积和根体积等)和根系生理(根系总吸收表面积、活跃吸收表面积和根系氧化力)指标。结果表明,播种后30 d,江苏省5个不同杂草稻种群根系形态生理均高于日本晴,杂草稻各种群的根系总根长、根系总表面积、总体积分别显著高于栽培稻36. 02%～91. 45%、63. 21%～90. 02%、61. 97%～149. 30%;杂草稻各种群的根系总吸收表面积、活跃吸收表面积、根系氧化力分别显著高于栽培稻24. 98%～124. 43%、42. 60%～163. 30%、31. 95%～67. 37%。研究结果揭示了杂草稻在苗期具有较强的根系活性,从根系发育及代谢能力角度进一步阐述了杂草稻的竞争优势和抗逆性机制。     

马铃薯根系分泌物及氨基酸对萎缩芽孢杆菌QHZ3趋化成膜的影响

通过土培收集、硅烷衍生化分离、气质联用鉴定马铃薯苗期、现蕾期及盛花期根系分泌物的主要成分，并采用半固体平板法、类毛细管法和结晶紫染色法比较观察马铃薯不同生育时期根系分泌物及氨基酸对萎缩芽孢杆菌QHZ3趋化成膜的影响，以揭示菌株QHZ3在马铃薯根际的定殖机制。马铃薯根系分泌物鉴定中发现了5种氨基酸：脯氨酸、甘氨酸、天冬氨酸、苯丙氨酸和酪氨酸。定性试验显示，马铃薯不同生育时期的根系分泌物和除脯氨酸之外的其他4种氨基酸均对菌株QHZ3具有显著的正趋化作用，并以甘氨酸的作用最强，其趋化圈直径（6.40 cm）是对照（3.48 cm）的1.84倍；定量试验结果表明，根系分泌物（120 μg·mL^-1和240 μg·mL^-1）、甘氨酸（10 ~50 μmol·L^-1）、天冬氨酸（50~75 μmol·L^-1）和苯丙氨酸（25~50 μmol·L^-1）均对菌株QHZ3有显著正趋化作用，尤其以25 μmol·L^-1的甘氨酸趋化性指数最大，其毛细管中细菌数量（5.13×10⁵ CFU·mL^-1）达到对照组（1.53×10⁵ CFU·mL^-1）的3.3倍；结晶紫染色法显示，现蕾期和盛花期根系分泌物以及甘氨酸（25~100 μmol·L^-1）、脯氨酸（75~100 μmol·L^-1）和苯丙氨酸（25~100 μmol·L^-1）均对菌株QHZ3生物膜的形成有显著促进作用。根系分泌物和氨基酸均对菌株QHZ3在马铃薯根际趋化成膜具有促进作用，但5种氨基酸的作用各不相同，其中天冬氨酸和酪氨酸显著影响菌株的趋化作用，脯氨酸显著影响了菌株生物膜的形成，而甘氨酸和苯丙氨酸则对菌株的趋化和成膜兼具显著效果。     

干旱胁迫下3个油菜品种地上、地下部生长特征与抗旱性的关系

为了探索干旱胁迫下不同抗旱性油菜品种的地上、地下部生长特征与抗旱性的关系，通过土柱栽培试验，对油菜品种DR1、DR2和DR3在不同水分处理条件下不同土层根量、地上部生物量、冠层覆盖面积及抗旱性之间的关系进行研究。结果表明：3个品种在水分胁迫和正常供水条件下产量和根系生物量在品种间均达到显著性差异，3个品种的抗旱能力大小依次为：DR1>DR3>DR2；不同水分处理下油菜的根系主要分布于0~30 cm土层，占根系总量的70%以上；在干旱胁迫下，3个品种DR1、DR2和DR3的总根量分别减少了22.53%、24.17%和24.53%，但仍表现出抗旱性强的品种DR1的根系总量最大,达到12.07 g，其次为品种DR3和DR2；在大于30cm的土层中，DR1的根系量占到总根量的31.5%，这表明根系垂直分布量的多少对抗旱性的影响较大，同时植株冠层面积、总生物量、根系干重与抗旱性的直接通径系数分别为0.5861、0.4514、0.5715，说明除了根系外，大的冠层面积可减少地表蒸发有利于作物抗旱。     

生物炭对甜瓜幼苗质量与根系生理特性的影响

于2021年4—7月，采用盆栽方法，在育苗营养土中设置了不同的生物炭添加量（分别为0、10、20、40、80 g·kg^-1），研究生物炭对土壤物理性状、甜瓜幼苗根表面积、根系生理指标以及幼苗质量的影响。结果显示：生物炭不同添加量均能改善土壤物理性状，以80 g·kg^-1应用效果最好，提高了土壤pH和含水量，分别比CK提高了1.86%和3.16%；且降低了土壤容重，比CK降低5.93%。与CK相比，生物炭不同添加量均能提高甜瓜根系生理活性，以40 g·kg^-1应用效果最好，在甜瓜出苗后25 d，根系活力、根系中硝态氮含量、NR、CAT、POD、SOD、APX、PPO活性分别比CK提高了20.88%、5.70%、126.67%、10.47%、23.42%、31.58%、54.21%、62.88%。生物炭不同添加量均能提高甜瓜根表面积，以40 g·kg^-1应用效果最好，在甜瓜出苗后25 d，根体积、根系总吸收面积、活跃吸收面积、活跃吸收面积百分比、根比表面分别比CK提高了21.07%、40.19%、71.82%、22.56%和15.76%。生物炭不同添加量均能提高甜瓜幼苗质量，以40 g·kg^-1应用效果最好，在甜瓜出苗后25 d，株高、茎粗、叶面积、全株鲜质量、全株干质量、根冠比、壮苗指数分别比CK提高了34.87%、31.71%、33.91%、31.92%、45.10%、64.94%、43.33%。研究表明添加生物炭能够促进甜瓜幼苗形态建成，通过调节根系生理活性和改善根际土壤环境来提高幼苗质量。     

Mercury, arsenic, and cadmium in fish, water, and sediment of American Falls Reservoir, Idaho, 1974.

Mercury and cadmium were found in fish, water, and sediment of American Falls Reservoir (AFR), Idaho. Mercury and cadmium levels in some fish exceeded human health standards set by the Food and Drug Administration, U.S. Department of Health, Education and Welfare, and the World Health Organization. Analyses performed on the flesh of rainbow trout showed mercury residues of up to 1.20 mg/kg, which were higher than residues previously reported in trout collected in 1970 and 1971 from AFR. Cadmium residue levels were as high as 0.80 mg/kg. Although arsenic was found in reservoir sediment at levels of 1.36-2.40 mg/kg, it was not detected in fish.     

Intestinal uptake,metabolism, and transport of naphthol: In vitro capacity,requirements, and inhibition

The metabolism and transport of [¹⁴C]-naphthol were investigated in sacs of rat small intestine to better understand metabolism of the pesticide carbaryl (which contains naphthol) in the intestine. The capacity to synthesize polar ¹⁴C-labeled metabolites was approximately saturated at 50 μM naphthol. The metabolic capacity of the cranial small intestine was about two times the capacity of the caudal. Anaerobic incubation severely suppressed naphthol metabolism. Sodiumfree medium suppressed metabolism only slightly but altered transport of water and of the polar ¹⁴C-labeled metabolites to serosal and mucosal fluids; the effect on metabolite transport cannot be explained by the effects of sodium on water movements, however. Calcium-free medium did not affect metabolism or metabolite transport; 2,4-dinitrophenol, and possibly phlorizin, but not ouabain, suppressed naphthol metabolism in specific regions of the intestine. Each of the three inhibitors altered metabolite transport. It is concluded that the capacity to conjugate naphthol in the small intestine is greater in the cranial than caudal regions; the quantity of naphthol taken up from the medium is proportional to the rate of formation of the polar metabolite, naphthyl glucuronide; addition of 2,4-dinitrophenol, phlorizin, or ouabain, or deletion of sodium, perturbed the transport of the polar metabolite, but the perturbance could not be explained by the effect on rate or direction of fluid transfer and indicated an effect on cellular permeability or on transport mechanisms; the effect of the three inhibitors and possibly of elevated naphthol concentrations (to 520 μM) in the medium on metabolite transport may be by a sodium interaction; the latter suggests that naphthol may be toxic to the intestine at concentrations approaching 100 to 1000 μM.     

Population dynamics of Rhizoctonia,Oculimacula, and Microdochium species in soil,roots, and stems of English wheat crops

This study aimed to elucidate the population dynamics of Rhizoctonia, Oculimacula, and Microdochium species, causing the stem base disease complex of sharp eyespot, eyespot, and brown foot rot in cereals. Pathogen DNA in soil, roots, and stem fractions, and disease expression were quantified in 102 English wheat fields in two seasons. Weather data for each site was collected to determine patterns that correlate with assessed diseases. Oculimacula spp. (66%) and R. solani AG 2-1 (63%) were most frequently detected in soil, followed by R. cerealis (54%) and Microdochium spp. (33%). Oculimacula spp. (89%) and R. cerealis (56%) predominated on roots and soil but were not associated with root rot symptoms, suggesting that these species used soil and roots for survival and as inoculum source. M. nivale was more frequently detected than M. majus on stems up to GS 21–30 and co-occurred on plant samples with O. acuformis. O. yallundae had higher DNA concentration than O. acuformis at the lower 5 cm basal region at GS 37–45. R. cerealis predominated in the upper 15 cm above the base beyond stem extension. Brown foot rot by Microdochium spp. was favoured by cool and wet autumns/winters and dominated in English wheat. Eyespot and sharp eyespot disease index by Oculimacula spp. and R. cerealis, respectively, correlated with wet/humid springs and summers. Results suggested that stem base pathogens generally coexisted; however, their abundance in time and space was influenced by favourable weather patterns and host development, with niche differentiation after stem extension.     

施肥对小麦、玉米和大豆连作土壤微生物群落功能多样性的影响

为了明确长期施肥和不施肥条件下作物连作对土壤微生物群落功能多样性的影响,以典型黑土为研究对象,选取长期定位实验站长期施肥和不施肥条件下的小麦、玉米和大豆连作处理,通过稀释平板法和Biolog Eco微平板法,测定土壤细菌、真菌、放线菌数量、碳源代谢活性等指标,为建立合理的农田管理措施提供数据支撑和理论依据。结果表明:长期施肥条件下大豆、小麦和玉米连作土壤细菌、真菌和放线菌数量均高于不施肥处理,且均以大豆连作处理细菌和真菌数量最高。不施肥条件下小麦和玉米连作土壤细菌总数较大豆连作处理分别下降了24.8%和31.0%,真菌总数分别下降了64.0%和51.2%;施肥条件下小麦和玉米连作土壤细菌总数则较大豆连作处理分别下降了29.0%和45.5%,真菌总数分别下降了26.7%和31.5%。Biolog结果表明,不施肥条件下小麦连作处理的平均颜色变化率(AWCD)高于玉米和大豆连作处理,施肥条件下则是大豆连作处理的AWCD值高于小麦和玉米连作处理。不施肥条件下大豆、玉米和小麦连作处理利用最多的碳源是碳水化合物类,施肥后不同连作处理利用最多的是碳水化合物类和多聚物类。大豆和小麦连作不施肥条件下土壤微生物利用率最高的碳源均是α-D-乳糖,施肥条件下利用率最高的碳源均是D,L-α-甘油,而不论施肥与否,玉米连作条件下土壤微生物利用率最高的碳源均是D-半乳糖醛酸;葡萄糖-1-磷酸盐和γ-羟基丁酸是农田黑土微生物群落特异利用的关键碳源。主成分分析得出,施肥对土壤微生物碳源代谢能力的影响大于作物的影响。     

Allelopathic effects of Hemistepta lyrata on the germination and growth of wheat, sorghum, cucumber, rape, and radish seeds

The allelopathic effects of a water extract from Hemistepta lyrata were tested on the seeds of selected crops in Petri dishes. The results showed that the extract strongly inhibited the germination and seedling growth of wheat ( Triticum aestivum ), rape ( Brassica campestris ), and radish ( Raphanus sativus ), but only slightly inhibited those of sorghum ( Sorghum vulgare ) and cucumber ( Cucumis sativus ). The extract stimulated the growth of roots and hypocotyls at lower concentrations, while it inhibited their growth at higher concentrations. The malondialdehyde (MDA) content of cucumber and radish increased after treatment with the extract. These results indicated that the MDA concentration in plants is one important aspect of the allelopathic effects of H. lyrata .     

Germination, emergence, and dormancy of Mimosa pudica

Mimosa pudica (common sensitive plant) is a problematic weed in many crops in tropical countries. Eight experiments were conducted to determine the effects of light, seed scarification, temperature, salt and osmotic stress, pH, burial depth, and rice residue on the germination, seedling emergence, and dormancy of M. pudica seeds. Scarification released the seeds from dormancy and stimulated germination, though the germination of the scarified seeds was not influenced by light. The scarification results indicate that a hard seed coat is the primary mechanism that restricts germination. The germination increased markedly with the exposure to high temperature "pretreatment" (e.g. 150°C), which was achieved by placing non-scarified seeds in an oven for 5 min followed by incubation at 35/25°C day/night temperatures for 14 days. The germination of the scarified seeds was tolerant of salt and osmotic stress, as some seeds germinated even at 250 mmol L⁻¹ NaCl (23%) and at an osmotic potential of −0.8 MPa (5%). The germination of the scarified seeds was >74% over a pH range of 5–10. The seedling emergence of the scarified seeds was 73–88% at depths of 0–2 cm and it gradually decreased with an increasing depth, with no seedling emergence at the 8 cm depth. The rice residue applied to the soil surface at rates of ≤6 t ha⁻¹ did not influence the seedling emergence and dry weight. The information gained from this study identifies some of the factors that facilitate M. pudica becoming a widespread weed in the humid tropics and might help in developing components of integrated weed management practises to control this weed.     

DDT and BHC residues in some body tissues of goats, buffalo, and chickens, Lucknow, India

Muscle, liver, brain, and abdominal body fat samples of goats, buffalo, and chickens, all common meat sources in India, were analyzed by gas-liquid chromatography (GLC) for residues of DDT and benzene hexachloride (BHC). A few samples of goat and buffalo bone marrow were also included. Relatively high residue levels were found in body fat and bone marrow compared with other tissues. DDT and BHC residue levels were highest in chicken body fat, averaging 4.157 ppm sigma DDT and 3.879 ppm BHC. DDT content was much higher in goat and buffalo bone marrow than in the corresponding body fat. DDT levels in brain samples were highest (0.138 ppm) in buffalo. p,p'-TDE levels were higher than p,p'-DDE levels in buffalo; overall DDT levels were lowest in goats. BHC residues were generally low in buffalo; alpha-BHC accounted for most BHC residues in brain tissues. Greater accumulations of DDT and BHC were found in leg muscles than in breast muscles of chickens.     

四种常用三唑类杀菌剂在香蕉上残留行为及使用评价研究

采用田间试验研究了戊唑醇、氟环唑、苯醚甲环唑、丙环唑等4种常用三唑类杀菌剂在香蕉上的残留行为, 并比较了戊唑醇在套袋与不套袋情况下的最终残留量。研究结果表明：香蕉上戊唑醇、氟环唑、苯醚甲环唑、丙环唑的降解半衰期分别为10.8~14.1、8.1~9.5、7.9~12.9、9.4~15.6 d。在试验剂量条件下, 末次施药后42 d时, 戊唑醇(不套袋)、戊唑醇(套袋)、氟环唑、苯醚甲环唑、丙环唑在蕉肉中的残留量分别为：0.01~0.04、<0.01、0.01~0.08、≤0.01 mg/kg和0.02~0.07 mg/kg; 在全蕉上的残留量分别为0.05~0.47、<0.01、0.10~0.36、0.03~0.19 mg/kg 和0.05~0.32 mg/kg。香蕉果肉占全果的比例约为55%~75 %, 全果的残留量约为果肉2~19倍, 表明香蕉中戊唑醇、氟环唑、苯醚甲环唑、丙环唑主要残存在果皮上。戊唑醇防治香蕉叶斑病, 在套袋情况下可以显著地减少其在收获期香蕉上的残留。     

Insecticidal activity of N,N-diethyl-, N,N-dipropyl-, N,n-di-isopropyl-, and n,n-di-isobutylalkanamides against mosquito larvae

N,N-Diethyl-, N,N-dipropyl-, N,N-di-isopropyl, and N,N-di-isobutylalkanamides in which the acyl moiety ranged from C₈ to C₂₁ were synthesised, and their larvicidal activity was determined against the first-instar larvae of the southern house mosquito Culex quinquefasciatus Say. The four homologous series of amides generally showed an increase in their larvicidal activity as the carbon number in the acyl moiety of the amides increased, until the activity reached a maximum. Subsequently, an increment of carbon number resulted in declining activity in the higher homologues, until the activity disappeared. N,N-Diethyltetradecanamide, N,N-dipropylundecanamide, N,N-di-isopropylundecanamide, and N,N-di-isobutlynonanamide or -dodecanamide were the most active compounds in their respective homologous series of amides; however, they were less active than their analogous N,N-dimethylalkanamides previously studied.