Subspecies-level variation in the phytoextraction of weathered p,p'-DDE by Cucurbita pepo

Previous studies indicate that Cucurbita pepo can phytoextract highly weathered persistent organic pollutants (POPs) from soil and translocate large quantities to aerial tissues. To investigate intraspecific variability in uptake potential, a field study was conducted to quantify the phytoextraction of weathered p,p'-DDE by 21 cultivar varieties of summer squash from two distinct subspecies, C. pepo ssp texana and C. pepo ssp pepo. Significant differences exist between the two subspecies, with average root and stem to soil bioconcentration factors (BCF, dry weight ratio of contaminant concentration in the vegetation to that in the soil) of 7.22 and 5.40 for ssp pepo and of 2.37 and 0.454 for spp texana, respectively. The amounts of weathered p,p-DDE extracted from the soil by ssp pepo and ssp texana were 0.301 and 0.065%, respectively, with maximum values within each subspecies of 0.780 and 0.182%, respectively. The quantities of 14 inorganic elements were determined in both the soil and tissues (roots, stems, leaves, and fruit) of all 21 cultivar varieties. Phosphorus concentrations in the tissues of ssp pepo were 14 (fruit)-73% (stems) greater than those of ssp texana. These data support our hypothesis that the unique ability of certain cultivars of C. pepo to phytoextract highly weathered POPs from soil is the result of low molecular weight organic acid exudation as a unique phosphorus acquisition mechanism.     

Surfactants differentially impact p,p'-DDE accumulation by plant and earthworm species

The effect of four surfactants (Triton X-100, Tween-80, rhamnolipids, cyclodextrin) at 100-1000 mg/L on p,p'-DDE phytoextraction by Cucurbita pepo (zucchini) under field conditions and p,p'-DDE bioaccumulation by earthworm species (Eisenia fetida, Lumbricus terrestris) under laboratory conditions was investigated. Abiotically, surfactants (except cyclodextrin) increased contaminant desorption from soil by 4-fold, with higher concentrations generally promoting greater release. Cyclodextrin had no effect on DDE desorption. DDE concentrations in unamended zucchini roots and stems were 30- and 7.8-fold greater than soil levels, respectively, and 1.6% of the contaminant was extracted from the soil. The surfactant effects were cultivar specific. Triton X-100 increased DDE uptake in "Costata" by 2.6-fold, yielding 5% contaminant phytoextraction. In "Goldrush", DDE accumulation decreased by 69% across all surfactants. Surfactants significantly increased DDE bioaccumulation by earthworms. For E. fetida with all surfactants and L. terrestriswith Triton X-100 and cyclodextrin, DDE accumulation increased 2.5-7.2-fold, paralleling abiotic desorption. However, Tween-80 and rhamnolipids increased DDE accumulation in L. terrestris by 74 and 36 fold, respectively. These dramatic increases in contaminant bioaccumulation do not correlate with the increased availability observed abiotically. Surfactant-mediated increases in contaminant bioavailability are an unexpectedly complex process and clearly present unanticipated concerns over pollutant exposure to nontarget organisms.     

RESIDUES OF p, p'-DDE AND DICOFOL IN MILK OF DAIRY COWS FED COMMERCIALLY PRODUCED APPLE POMACE

Residues of the miticide, dicofol, used in orchards, as well as p,p'-DDE a metabolite of p,p'-DDT present as an impurity in dicofol, were found in each commercial apple pomace sampled at several locations in Central New York. Traces of dicofol and p,p'-DDE were found in milk when cows were experimentally fed one of the pomaces for 9 days. These compounds were also detected in the milk of cows which had been fed by a dairy farmer on a practical basis for several months. It was judged that the milk residues were too low to be of health significance to consumers.     

Distribution and elimination of polychlorinated dibenzo-p-dioxins,dibenzofurans, biphenyls,and p,p'-DDE in tissues of bald eagles from the Upper Peninsula of Michigan

Liver, muscle, fat, kidney, and gall bladder of eight bald eagles (Haliaeetus leucocephalus) found dead in the Upper Peninsula of Michigan during 2000 were analyzed for the presence of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (including coplanar PCBs), p,p'-DDE, and hexachlorobenzene (HCB). Necropsy results showed that the birds suffered from peritonitis, bacterial infection, or trauma. Concentrations of PCDD/DFs in livers ranged from 23 to 4500 pg/g on a wet weight basis (wet wt), whereas the least concentrations were found in blood plasma of bald eagle nestlings (2.3-49 pg/g, wet wt). A maximum total PCB concentration of 280,000 ng/g, wet wt, was found in the liver of a dead bald eagle affected by peritonitis. The greatest concentrations of p,p'-DDE and HCB in eagle livers were 17,000 and 120 ng/g, wet wt, respectively. Eagles with elevated 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or total PCB concentrations tended to have great TCDD/TCDF or PCB126/PCB77 ratios, hypothesized to be due to induction of cytochrome P450 enzymes and subsequent metabolism of TCDF and PCB77. Concentrations of TCDD toxic equivalents (TEQs) in the tissues of bald eagles exceeded the thresholds for toxicity in a few avian species. Non-ortho coplanar PCBs accounted for 68-88% of the total TEQs in bald eagle tissues. PCDDs and PCDFs collectively accounted for, on average, 17% of the total TEQs. On the basis of the analysis of a single gall bladder with bile, biliary excretion rates of PCDDs, PCDFs, and PCBs were estimated as 0.015-0.02% per day.     

HCB, p,p'-DDE and PCB ontogenetic transfer and magnification in bluefin tuna (Thunnus thynnus) from the Mediterranean Sea

The bluefin tuna, Thunnus thynnus (Linnaeus 1758), is biologically and economically important in the Atlantic--Mediterranean ecosystems. Bluefin tuna feed on diverse food items depending on their age, thus they occupy different trophic levels during their lifespan. Hexachlorobenzene (HCB), p,p'-DDE and polychlorinated biphenyls (PCBs) are well-known persistent organic pollutants (POPs) in the Mediterranean basin. The relationship between stable isotopes of nitrogen (N) and the POP residue levels in tissues has recently increased knowledge on the link between the trophic levels and the contaminant accumulation. Trophic levels were estimated by using 15N/14N ratio (delta15N) and HCB, p,p'-DDE, and forty-three PCBs were quantified in bluefin tuna from the southern Tyrrhenian Sea. Results showed that changes in PCB and p,p'-DDE concentrations were a function of size and trophic level, while no correlations were observed for HCB. Apart from HCB and PCB nos. 101, 207, 95, 158, and 60 + 56, which did not show any significant increase per trophic level, the other PCBs and the p,p'-DDE increased significantly. The ontogenetic magnification factor of PCBs was 6.6 +/- 0.5, which was significantly (12 times) higher (p < 0.05) than the values found for p,p'-DDE (1.4) and HCB (1.4).     

NaNO3对两种杜氏藻生长及色素积累的影响

研究NaNO3对两种杜氏藻Dunaliella salina和Dunaliella parva生长速度、色素积累的影响和NaNO3的吸收规律。结果表明,NaNO3浓度为1.5 mmol/L时,D.salina生长最快,最高密度76.4×104cell/mL;对照组为16.3×104cell/mL;低氮有利于D.salinaβ-胡萝卜素积累,β-胡萝卜素最大值105 mg/g出现在0.5 mmol/L NaNO3样中,对照组为45 mg/g;较高的NaNO3有利于叶绿素a的合成;藻液pH开始3 d~5 d急剧上升,后在波动中下降。对D.parva来说,NaNO3浓度为2.5 mmol/L时生长最快,细胞最高密度为295×104cell/mL,对照组为15×104cell/mL;在实验范围内,NaNO3浓度越高,β-胡萝卜素含量越高,β-胡萝卜素最大值为37.5 mg/g,叶绿素最大值为65 mg/g;建立了两种杜氏藻对NaNO3利用的动力学方程。     

HACCP在农作物生产中的应用

HACCP是一种食品安全保证体系,最早起源于20世纪60年代初美国对航天食品的管理,现在已成为很多国家普遍接受的最重要的食品安全管理体系.HACCP强调以预防为主,包括HA(即危害分析,Hazard Analysis)和CCP(即关键控制点,Critical Control Point)两个部分.     

有待开发的高原作物--青稞

青稞,又称裸大麦(HordeumValgereVar.Muda),亦称米大麦、裸麦、元麦、糖麦等,是大麦的一个变种,一年生或越年生草本植物。青稞的生育期较短,比小麦早熟,且能适应迟种早收。青稞成熟后种子与耔壳分离,容易脱落成裸粒,种皮有灰白色、灰色、紫色、紫黑色等,因种植地区和品种的不同而异。中国的青藏高原是野生大麦和青稞栽培的起源地,也是优质青稞的丰产地。青稞的最高单产世界记录出现在青藏高原,1978年,青海西宁刘家寨乡西北园种植的8号青稞1.5亩,亩产673kg;1982年,西藏日喀则农科所的1.15亩喜玛拉雅6号青稞,创亩产805kg的高科所的1.15亩喜…     

烟草特有的N-亚硝胺形成、积累及其影响因素

烟草特有的Ｎ－亚硝胺（ＴＳＮＡ）是一组只在烟草、烟制品及烟气中发现的致癌物质。它们形成的前体物是烟草生物碱、硝酸盐和亚硝酸盐。大田正常生长及成熟的青烟不含ＴＳＮＡ，是采收后在调制、贮存陈化过程中逐步形成和积累起来的。凡影响前体物质的因素，都会影响烟草ＴＳＮＡ的形成、积累和含量。可通过控制两种前体物质的各种途径来降低烟草ＴＳＮＡ。     

Proximate Composition of Sweet Potato Greens in Relation to Cultivar, Harvest Date, Crop Year and Processing

Two sweet potato green cultivars, ‘Jewel’ and ‘Carver’, were produced during two crop years (1981 and 1982). The influence of cultivar, harvest date, crop year and processing on the proximate nutrient content of both varieties was determined. Results showed that overall nutrient content for both varieties were similar except for fat and ash content. Protein content in blanched and canned greens showed a decrease during the second and third collection periods, and the nutrient content from year to year remained constant. These data suggest that like other traditional vegetables, sweet potato greens can be preserved by traditional methods.     

玉米秸秆预处理研究

研究了秸秆粉碎后经过稀酸、稀碱和氨水3种预处理方式对玉米秸秆的影响;考查了预处理后秸秆的纤维素比例、糖转化率及对设备要求和环境污染等因素。研究表明:每种预处理对玉米秸秆的利用都有不同的影响,最终选择以质量分数4%H_2SO_4作为最佳预处理方式,此时的纤维素比例为65.1%,糖转化率达到47.8%。     

生物有机肥对烤烟氮磷钾积累、吸收和含量的影响

田间试验研究了生物有机肥对烤烟体内氮、磷、钾积累、吸收和含量的影响.结果表明,烤烟施用生物有机肥提高了烟株体内氮、磷、钾的积累;烤烟对氮素的积累为T3＞T2＞T1＞CK,单株分别积累氮素5.29、4.84、4.20、3.55g;对钾素的积累为T2＞T1＞T3＞CK,分别积累钾素4.92,4.59、4.58、3.92g.施用生物有机肥对烤烟氮素吸收速率的影响是50d前较对照明显升高;对磷素为50 d前施用50%生物有机肥的处理较对照增加,而75%生物有机肥的处理则较对照低;对钾的吸收速率团棵后逐渐增加,50d时达到高峰.施用生物有机肥增加了旺长期烟株体内氮、磷、钾的含量,促进了烟株生长,提高了烤后烟叶含钾量.     

甘蔗蔗糖积累的规律、影响因素及其调控机制的研究进展

甘蔗茎中积累高浓度蔗糖,其积累涉及到蔗糖的合成、运输和代谢等生理过程。本文对甘蔗茎中蔗糖积累的规律、影响因素及其调控机制的研究进展进行综述,并对今后研究的方向和路径作出展望。     

发芽大豆中异黄酮积累的光诱导作用研究

考察了不同光质、光强和光期对发芽大豆中的苯丙氨酸氨基裂解酶（PAL）活性及异黄酮合成积累的影响。试验结果表明，蓝光、白光、紫外光和红光等不同光质照射对发芽大豆的PAL活性和异黄酮含量有不同的影响。紫外光、蓝光和白光对发芽大豆的PAL活性和异黄酮的合成具有诱导促进作用，其中紫外光的促进作用最强，蓝光和白光的作用较弱。红光照射抑制发芽大豆的PAL活性和异黄酮的合成。紫外光照射强度试验表明，在0－60μmolm^-2s^-1光照强度范围内，发芽大豆的PAL活性和异黄酮含量随着紫外光照射强度的增加而显著提高。试验结果同时表明，红光照射显著地促进发芽大豆的生长，紫外光抑制生长，而蓝光和白光对发芽大豆的生长无明显影响。与黑暗（对照）相比，每天8h紫外光、16h红光和每天16h紫外光、8h红光交替处理，既可以促进发芽大豆的生长，对异黄酮的合成积累又具有明显的诱导促进作用。