烟株对Se(Ⅵ)和Se(Ⅳ)的吸收及叶片硒亚细胞分布

为了解烟草对不同价态硒的吸收及耐性机制,以水培烟株为材料,研究了不同浓度(0、2、5、10、20 mg/L)Se(Ⅵ)和Se(Ⅳ)对烟株硒吸收及叶片硒亚细胞分布的影响。结果表明:(1)水培液中加入Se(Ⅵ)和Se(Ⅳ)处理,低浓度(2 mg/L)对烟株生长有促进效果,高浓度(5 mg/L)有抑制作用,且相同硒浓度下表现为Se(Ⅳ)毒性大于Se(Ⅵ);(2)施硒处理烟株各部位硒含量增加显著,叶片以有机硒为主,无机硒主要以Se(Ⅳ)形态存储;(3)烟株叶片和茎秆对Se(Ⅵ)的亲和力大于Se(Ⅳ),而根系对Se(Ⅳ)的亲和力大于Se(Ⅵ);(4)烟株叶片吸收的硒主要贮存在细胞质和细胞壁中,其次为线粒体和叶绿体;(5)同等硒用量下,Se(Ⅵ)处理叶片总硒及细胞壁、细胞质中硒含量大于Se(Ⅳ)处理。综合分析得出,水培条件下,烟株对Se(Ⅵ)的吸收能力和耐受性均大于Se(Ⅳ),原因为烟株吸收的Se(Ⅵ)更易合成含硒氨基酸或蛋白质等积累在细胞质中和被细胞壁固定,进而缓解了硒的毒性。     

揭膜时期对烟株生长及烟叶产质量的影响

对地膜覆盖栽培的揭膜时期进行了研究。结果表明 ,在生育中期揭膜有利于成熟期烟株根系的生长 ,移栽后 30d揭膜处理的烟株根干重是全生育期盖膜处理的 1.72倍 ;盖膜导致了碱解氮、水溶性硼、速效钾、交换性镁等移动性强的养分在畦土表层富集。全生育期盖膜处理烟叶采收结束时 ,畦土表层 1.5cm深处土壤的碱解氮、水溶性硼、速效钾和交换性镁含量分别为 937.5 8mg/kg、1.60mg/kg、2 136.0 6mg/kg和 143.96mg/kg。试验还表明烟株生育中期揭膜 ,对提高烟叶产质量有一定效果 ,但上部烟叶烟碱含量较高     

生物炭对弱碱性土壤烤烟Cd吸收及转运富集特征的影响

[目的] 通过研究施用生物炭后烤烟对Cd的吸收效应及分配富集特征,来阐明生物炭对Cd污染植烟土壤的修复及对烤烟Cd含量的降低效果。 [方法] 于2015年采用盆栽试验（每盆装土25 kg）,选取豫中地区弱碱性土壤,外源添加Cd 0 mg/kg（G0）、50 mg/kg（G1）、100 mg/kg（G2）,分别添加生物炭0 g/盆（T0）、300 g/盆（T1）、600 g/盆（T2）,采用二因素试验共计9个处理,分别为:G0T0、G0T1、G0T2、G1T0、G1T1、G1T2、G2T0、G2T1、G2T2。测定各处理的土壤pH值、土壤有效态Cd含量,并分析烟株采收时不同部位Cd含量和烟株对Cd的转运及富集系数。 [结果] （1）土壤pH值随生物炭施用量的增加而升高,处理G2T2的土壤pH值最大,为7.81;土壤有效态Cd含量随生物炭施用量的增加呈现降低的趋势。（2）土壤Cd含量与烟株叶片中的Cd含量呈极显著正相关关系,且在同一污染水平下,施加生物炭后,烟株各部位叶对Cd的吸收呈显著降低的趋势。（3）施用生物炭的处理,烟株整体对Cd的转运系数降低,烟株根系对Cd的富集系数升高,叶片对Cd的富集系数降低。 [结论] 在Cd污染土壤种植烤烟时适量施用生物炭可以降低土壤有效态Cd含量,从而降低烟叶Cd含量。      

植烟土壤适宜施硒量研究

采用大田试验方式,在硒含量较低的土壤上施用亚硒酸钠,分析其对烤后烟叶硒含量、品质及卷烟产品安全性的影响,确定了植烟土壤适宜施硒量。结果表明：（1）烤后烟叶硒含量随土壤施硒量增加呈现抛物线趋势,当土壤施用亚硒酸钠量为13.50 kg/hm²时,烟叶硒含量最高。（2）土壤施用亚硒酸钠为6.75~11.25 kg/hm²时,烟叶烟碱等化学成分含量较适宜、可用性较高,评吸质量较好。（3）富硒烟叶可降低卷烟产品细胞急性毒性、致突变能力以及诱导细胞活性氧产生的能力。通过综合分析土壤施硒量对以上各种指标的影响,确定植烟土壤施用亚硒酸钠的适宜量为6.75~11.25 kg/hm²。     

两种稻田用除草剂残留对烟草危害的阈值研究

为指导烟稻轮作区稻田用除草剂2,4-滴丁酯和氯氟吡氧乙酸的合理使用,通过室内盆栽与大田试验,研究了两种除草剂在土壤和烟株中的残留和消解动态,以及烟株药害症状和内源激素含量变化。结果表明：（1）两种除草剂残留均可导致烟株矮化,茎秆扭曲,烟叶卷曲黄化;（2）两种除草剂残留导致不同部位烟叶IAA和GA₃含量显著降低,ABA含量显著升高（p<0.05）;（3）随施用剂量和处理时间增加,两种除草剂残留对烟株农艺性状的抑制作用增强,以株高或叶面积抑制率为10%~15%为标准,2,4-滴丁酯和氯氟吡氧乙酸的致害阈值在土壤中分别为1.022和0.053 mg/kg,在叶片中分别为0.047 8和0.027 6 mg/kg;（4）结合致害阈值得出2,4-滴丁酯和氯氟吡氧乙酸的田间安全间隔期分别为53 d和160 d。     

恩施烟区土壤硒分布特征及其与烟叶硒的关系

通过土壤与烟叶对应取样研究了恩施烟区土壤总硒的分布特征和烟叶硒与土壤硒的关系。结果表明,恩施烟区土壤硒有98%以上的区域处于"足"和"富"以上的水平,平均含量达到了(0.63±0.56)mg/kg。烟叶硒含量上部叶最高(0.18±0.13)mg/kg,中部叶和下部叶基本相当(0.17±0.11)mg/kg。不同部位烟叶硒含量与土壤硒含量的相关性表现出明显差异,上中部叶与土壤硒含量的相关性达到了极显著正相关(r分别为0.686**、0.480**,r0.01为0.302,n=70),下部叶硒含量与土壤硒含量的相关性未达到显著水平(r=0.123,n=70)。土壤"富"硒区烟叶硒含量(上、中、下部分别为0.24、0.19和0.20 mg/kg)明显高于"少"硒区和"足"硒区(上、中、下部分别为0.17、0.14和0.14 mg/kg),"富"硒区中上部烟叶硒含量与土壤硒含量表现出极显著正相关,在"少"硒区和"足"硒区烟叶硒含量与土壤硒含量没有明显的相关性。     

恩施州植烟土壤及烟叶硒含量状况分析

调查了恩施州植烟土壤及烟叶硒含量状况。结果表明:(1)恩施州植烟土壤硒含量平均为0.661 mg/kg,从土壤总硒水平来看,恩施土壤属于富硒土壤。烟叶硒含量平均为0.216 mg/kg,并表现为B2F>C3F>X2F,高于我国其他烟区。(2)恩施土壤硒的垂直地理分布特性明显,即随海拔高度的升高而极显著地增加;土壤硒含量与土壤中有机质、碱解氮、速效磷、速效钾等大量元素具有极显著正相关,而与pH的相关性没有达到显著水平。当土壤等级为足硒和富硒土壤时,土壤中主要养分含量处于烟叶生长所需的适宜范围内。(3)在相对较高的硒含量土壤中,烟叶对硒的吸收累积强于低硒土壤。8个植烟县(市)土壤和烟叶硒含量的相关性均为正相关。     

氯素营养水平对烤烟生长发育及产质量的影响

为了探索福建烟区烤烟土壤氯素的适宜用量和烟叶氯含量的适宜水平,采用盆栽和大田试验方法,分析了土壤中不同水溶性氯含量和不同氯肥用量对烟株生长发育、干物质积累、经济性状、评吸质量的影响。结果显示,福建烟区土壤水溶性氯含量25~35 mg/kg为适宜,15~25 mg/kg 为潜在缺乏,低于15 mg/kg 为缺乏,高于35 mg/kg为丰富;高于330 mg/kg为严重过量,导致烤烟中毒。烟叶中氯含量0.46%~0.66%为适宜,大于0.99%时,烟叶品质受到严重影响。     

水肥一体化条件下烤烟氮素营养高效利用研究

  目的  为探究水肥一体化技术对烤烟氮素营养利用效率的影响。  方法  试验设置了空白对照（CK）、常规栽培（FP）和水肥一体化（DF）3个处理,通过2年的田间试验和1年的盆栽实验,检测了3个处理不同时期烟株的干物质积累量和氮素吸收量,对比了3个处理不同生育时期烟株根系生长发育情况,并测定了常规栽培（FP）和水肥一体化（DF）处理烟叶硝酸还原酶（NR）和谷氨酰胺合成酶（GS）的活性和烤烟氮代谢相关的NITR和GS基因的表达量。  结果  （1）DF处理NR活性在移栽20 d和40 d均明显高于FP处理,分别是FP处理的1.26倍和1.31倍,NITR基因的相对表达量也均高于FP处理,在移栽80 d后,DF处理NR活性大幅下降60.81%,而FP处理下降较缓慢;（2）DF处理较FP处理能显著提高烟株根系活力和根体积,促进烟株根系生长发育和形态建成,使烟株氮肥表观利用率提高了93.21%,氮肥偏生产力提高了15.24%,土壤氮素依存率降低了15.01%;（3）DF处理和FP处理烟株干物质和氮素积累变化规律趋势相同,但DF处理的干物质和氮素积累量以及积累速率均较FP处理有明显提升,且DF处理干物质积累和氮素吸收高峰提前,烟株生育后期氮素调亏,成熟落黄较好,烤后烟叶品质较高。  结论  采用水肥一体化技术可以有效调控烟株对氮素的吸收,提高氮素利用率,对促进烟株干物质积累和产质量的提高有积极的影响。      

ABT生根粉对烤烟产质及生理变化的影响

在烤烟移栽前５～７天，用ＡＢＴ生根粉４号１５ｐｐｍ浓度的溶液喷施烟苗。结果表明：施用ＡＢＴ生根粉的烟株根系发达，侧根数量剧增，呈簇状，根系干、鲜重明显增加；烟株株高、茎粗、叶数、单叶重（生物学性状）明显优于对照；处理烟株总核酸含量减少（ＤＮＡ增加，ＲＮＡ含量减少），旺长期叶片的光合色素增加，有机酸含量降低（苹果酸减少，柠檬酸增加），碳水化合物含量增加（还原糖降低）；烤后烟叶处理黄烟率高，对照青筋黄片偏多。使用生根粉的烟叶总糖降低，蛋白质含量增高，烟叶化学成分较对照更趋于协调。     

土壤施硒对白肋烟含硒量的影响

盆栽试验结果表明,在本试验设定的土壤施硒范围内,白肋烟叶、根、茎的含硒量分别为3.8~210、2.2~57、1.4~42μg/g,呈叶 > 根 > 茎的分布规律,而且均与土壤施硒量呈极显著的正相关;白肋烟叶、茎、根的吸硒量分别为0.208~11.343、0.143~3.682、0.032~1.000 mg/pot,呈现叶 > 茎 > 根的分布规律,亦均与土壤施硒量呈极显著的正相关:叶、茎、根的吸硒量占烟株总吸硒量的比例分别为54.3%~70.8%、20.8%~37.5%、5.5%~9.5%,说明白肋烟的硒积累能力为叶 > 茎 > 根;白肋烟对土壤施硒的回收率为8.9%~18.1%。      

Uptake and distribution of added selenite and selenate by barley and red clover as influenced by sulphur

The uptake of added Se from selenite and selenate by barley and red clover was investigated in a pot experiment. Much more of selenate than of selenite was taken up but the Se concentrations in the plants declined more with time when selenate was the source. Increasing sulphate addition to the soil decreased the uptake of Se from selenate greatly and from selenite to a lesser extent. The ratio Se in the roots/Se in the tops shows that Se is more readily translocated from the roots when taken up from added selenate than from selenite. On the basis of these and other investigations it is concluded that selenite is a better source than selenate when the Se concentration in the plants has to be raised to a level sufficient for livestock nutrition.     

Distribution of selenium and phenolics in buckwheat plants grown from seeds soaked in Se solution and under different levels of UV-B radiation

Seeds of common buckwheat (Fagopyrum esculentum) were soaked in water, sodium selenate (5, 10 or 20 mg Se^VI/L), or sodium selenite (10 or 20 mg Se^IV/L) solutions. Plants grown from soaked seeds were exposed to reduced UV-B radiation, ambient, or enhanced UV-B. The mass fraction of selenium in leaves was much higher in plants obtained from seeds soaked with selenate (up to 185 ng/g) in comparison to selenite (up to 103 ng/g). In plants obtained from seeds soaked in water, regardless of UV-B levels, the highest concentration of selenium was found in leaves, where the values were between 45 and 66 ng Se/g. In buckwheat leaves 44.5–63.6 mg/100 g d.m. of fagopyrin was found, and in stems 14.3–26.4 mg/100 g d.m.; here no influence of seed soaking solution or UV-B exposure was found. The content of total flavonoids in leaves was 7.8–15.9% and in stems 1.4–4.1%.     

The effect of heat treatment on intrinsic and fortified selenium levels in cow's milk

The effects of two heat processing methods (pasteurisation and spray drying) routinely used in the processing of cow's milk and the production of infant formula powder on the selenium (Se) content of liquid milk, milk fortified with sodium selenite and sodium selenate were studied. Pasteurisation reduced intrinsic Se and selenate levels by 7.9% and 6.2% at p < 0.05 level and selenite levels by 7.0% at p > 0.05 level. Se losses following spray drying were 44.8% (p < 0.001), 11.4% (p < 0.01) and 10.0% (p < 0.01) for intrinsic selenium, selenite and selenate fortified milk, respectively. Total Se losses from unprocessed milk following processing (pasteurisation and spray drying) were 49.2% (p < 0.001), 17.6% (p < 0.001) and 15.6% (p < 0.001) for intrinsic selenium, selenite and selenate fortified milk, respectively.     

Effects of foliar and fruit addition of sodium selenate on selenium accumulation and fruit quality

BACKGROUND: We investigated the effects of the foliar and fruit application of sodium selenate on selenium (Se) accumulation, fruit growth and ripening in peach and pear. Trials were conducted in two growing seasons. In 2008 selenate was applied at a rate of 0.1 and 1.0 mg Se L^?1 to the leaves of peach. In 2009 selenate was applied at a rate of 1 mg Se L^?1 via foliar (LT) or fruit (FT) application to peach and pear. RESULTS: The foliar addition of selenate to peach resulted in an increase in Se concentration both in leaves and fruit. The higher Se content in fruit resulted in an increase in flesh firmness and a decrease in soluble solid content. LT significantly increased the Se content in the leaves and fruit of peach and pear, and leaves showed the highest Se concentrations. FT increased the fruit Se concentration in both crops, and it was more effective than LT in increasing Se content. After storage, flesh firmness decreased in all treatments, but it was significantly higher in FT compared to LT and control samples. CONCLUSION: Foliar and fruit selenium spraying appeared effective in increasing the Se content of fruit in peach and pear. The enhanced Se concentration affected the shelf life of fruit, delaying the reduction in flesh firmness and fruit ripening, thus positively affecting fruit storage. Copyright © 2011 Society of Chemical Industry     

Combined speciation analysis by X-ray absorption near-edge structure spectroscopy, ion chromatography, and solid-phase microextraction gas chromatography-mass spectrometry to evaluate biotreatment of concentrated selenium wastewaters

In this study we evaluate the potential of anaerobic granular sludge as an inoculum for the bioremediation of selenium-contaminated waters using species-specific analytical methods. Solid species formed by microbial reduction were investigated using X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K-edge. Furthermore, dissolved selenium species were specifically determined by ion chromatography (IC) and solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). Least-squares linear combination of the XANES spectra for samples incubated with the highest selenate/selenite concentrations (10(-3) M) show the predominance of elemental selenium and a Se(-I) selenide, such as ferroselite, the thermodynamically most stable iron selenide. In contrast, elemental selenium and Se(-II) selenides are the main species detected at the lower selenate/selenite concentrations. In each repeated fed batch incubation, most aqueous selenite anions were converted into solid selenium species, regardless of the type of electron donor used (acetate or H(2)/CO(2)) and the selenium concentration applied. On the other hand, at higher concentrations of selenate (10(-4) and 10(-3) M), significant amounts of the oxyanion remained unconverted after consecutive incubations. SPME-GC-MS demonstrated selenium alkylation with both electron donors investigated, as dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe). Selenite was even more alkylated in the presence of H(2)/CO(2) (maximum 2156 μg of Se/L of DMSe + DMDSe) as compared to acetate (maximum 50 μg of Se/L). In contrast, selenate was less alkylated using both electron donors (maximum 166 and 3 μg of Se/L, respectively). The high alkylation potential for selenite limits its bioremediation in selenium laden waters involving H(2)/CO(2) as the electron donor despite the fact that nontoxic elemental selenium and thermodynamically stable metal selenide species are formed.     

Factors affecting soluble selenium removal by a selenate-reducing bacterium Bacillus sp. SF-1

High concentrations of soluble selenium, selenate and selenite, have acute and chronic toxicity toward living things. With the aim of developing a biological process for selenium removal, the effects of a variety of parameters on the reduction of soluble selenium by a Bacillus sp. strain SF-1, which is capable of reductively transforming selenate into selenite and, subsequently, into nontoxic insoluble elemental selenium, were studied. The bacterial strain could effectively reduce 20 mM of selenate to selenite and 2 mM of selenite to elemental selenium in the presence of an appropriate carbon source and in the absence of oxygen. The reduction rate of selenate to selenite was much higher than that of selenite to elemental selenium, resulting in the transient accumulation of selenite during selenate reduction. The selenate reduction rate increased with increases in the selenate concentration up to 20 mM, while the rate of selenite reduction decreased sharply at selenite concentrations of more than 2 mM. The elemental selenium transformed from selenate via selenite was found both inside and outside the cells. Bacillus sp. SF-1 was able to utilize a variety of organic acids or sugars as a carbon source in selenate reduction. Although the copresence of sulfate did not inhibit selenate reduction, it was completely inhibited by some other oxyanions, including nitrate. A model sequencing batch system using the bacterial strain was developed and exhibited good performance in the treatment of wastewater containing high concentrations of selenate.     

Factors affecting soluble selenium removal by a selenate-reducing bacterium Bacillus sp. SF-1

High concentrations of soluble selenium, selenate and selenite, have acute and chronic toxicity toward living things. With the aim of developing a biological process for selenium removal, the effects of a variety of parameters on the reduction of soluble selenium by a Bacillus sp. strain SF-1, which is capable of reductively transforming selenate into selenite and, subsequently, into nontoxic insoluble elemental selenium, were studied. The bacterial strain could effectively reduce 20 mM of selenate to selenite and 2 mM of selenite to elemental selenium in the presence of an appropriate carbon source and in the absence of oxygen. The reduction rate of selenate to selenite was much higher than that of selenite to elemental selenium, resulting in the transient accumulation of selenite during selenate reduction. The selenate reduction rate increased with increases in the selenate concentration up to 20 mM, while the rate of selenite reduction decreased sharply at selenite concentrations of more than 2 mM. The elemental selenium transformed from selenate via selenite was found both inside and outside the cells. Bacillus sp. SF-1 was able to utilize a variety of organic acids or sugars as a carbon source in selenate reduction. Although the copresence of sulfate did not inhibit selenate reduction, it was completely inhibited by some other oxyanions, including nitrate. A model sequencing batch system using the bacterial strain was developed and exhibited good performance in the treatment of wastewater containing high concentrations of selenate.     

Speciation of Se and DOC in soil solution and their relation to Se bioavailability

A 0.01 M CaCl(2) extraction is often used to asses the bioavailability of plant nutrients in soils. However, almost no correlation was found between selenium (Se) in the soil extraction and Se content in grass. The recently developed anion Donnan membrane technique was used to analyze chemical speciation of Se in the 0.01 M CaCl(2) extractions of grassland soils and fractionation of DOC (dissolved organic carbon). The results show that most of Se (67-86%) in the extractions (15 samples) are colloidal-sized Se. Only 13-34% of extractable Se are selenate, selenite and small organic Se (<1 nm). Colloidal Se is, most likely, Se bound to or incorporated in colloidal-sized organic matter. The dominant form of small Se compounds (selenate, selenite/small organic compounds) depends on soil. A total of 47-85% of DOC is colloidal-sized and 15-53% are small organic molecules (<1 nm). In combination with soluble S (sulfur) and/or P (phosphor), concentration of small DOC can explain most of the variability of Se content in grass. The results indicate that mineralization of organic Se is the most important factor that controls Se availability in soils. Competition with sulfate and phosphate needs to be taken into account. Further research is needed to verify if concentration of small DOC is a good indicator of mineralization of soil organic matter.