Selenium distribution and nitrate metabolism in hydroponic lettuce(Lactuca sativa L.): Effects of selenium forms and light spectra

A deficiency in selenium(Se) in the human diet is a worldwide problem. The intake of Se-rich vegetables can be a safe way to combat Se deficiency for humans. However, most leafy vegetables can accumulate a high content of nitrates, which poses a potential threat to human health. Light is an important environmental factor that regulates the uptake and distribution of mineral elements and nitrogen metabolism in plants. However, the effects of Se forms and light conditions, especially light spectra, on the uptake and translocation of Se and on nitrate reduction are poorly understood. In this study, lettuce(Lactuca sativa L.) was treated with exogenous Se applied as selenate(10 mmol L^-1) and selenite(0.5 mmol L^-1) and grown under five different light spectra: fluorescent light(FL), monochromatic red LED light(R), monochromatic blue LED light(B), and mixed red and blue LED light with a red to blue light ratio at 4(R/B=4), 8(R/B=8), and 12(R/B=12), respectively. The effects of light spectra and Se forms on plant growth, photosynthetic performance, Se accumulation and nitrate reduction were investigated. The results showed that the light spectra and Se forms had significant interactions for plant growth, foliar Se accumulation and nitrate reduction. The Se concentration and nitrate content in the leaves were negatively correlated with the percentage of red light from the light sources. Compared to Se applied as selenite, exogenous Se applied as selenate was more effective in reducing nitrate via promoting nitrate reductase and glutamate synthase activities. The lowest nitrate content and highest plant biomass were observed under R/B=8 for both the selenate and selenite treatments. The significant effect of the light spectra on the root concentration factor and translocation factor of Se resulted in marked variations in the Se concentrations in the roots and leaves. Compared with FL, red and blue LED light led to significant decreases in the foliar Se concentration. The results from this study suggest that the light spectra can contribute to Se distribution and accumulation to produce vegetables with better food quality.

Effects of Priming in Combination with Fungicides on Germination and Infestation of Lettuce (Lactuca sativa L.)

Two seed lots of lettuce (Lactuca sativa L.) cv. Krlowa Majowych were primed in polyethylene glycol (PEG) 8000 at -1.25MPa for 7 days in dark at 20C. Two fungicide treatments combined with PEG were used to control fungi: 1) Funaben T(0.1%) and Apron 35 SD (0.02%) were added to -1.25 MPa PEG solution (PEG+F); 2) After seed priming and drying,Funaben T was mixed at 5 g kg-1 and Apron 35 SD at 1 g kg-1 of seeds (PEG then F dust). PEG, PEG+F and PEG then F dusttreatments reduced significantly thermodormancy and increased the seed germination at 35C in both lots. PEG then Fdust treatment had the best effect on reducing seed thermodormancy at 35C, and increased seed germination to 64.5% inlot 1 and 72.0% in lot 2 compared to 0 in untreated. PEG and PEG then F dust treatments have accelerated germinationspeed at 20 and 15C in both lots. There was a significant reduction in seed infestation in which the seeds were treatedwith PEG+F and PEG then F dust compared to untreated seeds and PEG primed seeds. PEG priming enhanced seedinfestation considerably by Alternaria alternata, Penicillium spp., Rhizopus spp. and Ulocladium spp. Mycologicalanalysis showed higher frequency of Alternaria alternata and Ulocladium spp. in untreated seeds at 20C. Priming incombination with fungicides significantly alleviated the infestation of fungi, especially Alternaria alternata infestation.

Assessment of Heavy Metals and Microbial Pollution of Lettuce (<i>Lactuca sativa</i>) Cultivated in Two Sites (Paspanga and Tanghin) of Ouagadougou, Burkina Faso

Environmental pollution can have detrimental effects on crop yield and its consumers. The current study was designed to investigate the potential human health risks associated with the consumption of lettuce crop contaminated with toxic heavy metals and microbiological status. Irrigated water, soil and lettuce were analyzed by AAS technics for heavy metals including Cd, Cr, Cu, Mn, Ni, Pb and Zn. Transfer factor (TF), daily intake of metals (DIM) and health risk index (HRI) were also calculated. Microbial analysis was carried out for the presence foodborne pathogens. The results showed that the heavy metals contents were higher in the soil than wastewater and the vegetables. Heavy metals ranged (mg·Kg-1) for Cd (1.27 to 2.93), Cr (7.28 to 7.38), Cu (0.91 to 1.70), Mn (0.29 to 6.60), Ni (1.74 to 2.16), Pb (1.32 to 1.69), Zn (3.08 to 3.79);and were higher than the WHO maximum limit permissible (ML) in vegetables. HRI TF values designated an enhanced bio-contamination. Microbial numeration revealed the presence of spoiler and pathogenic microorganisms. The lettuce tested was not safe for human use, especially for direct consumption by human beings.

TDZ对莴苣(Lactuca sativa L.)器官发生及乙烯形成的影响

为了研究TDZ在植物器官发生中的生理作用，用不同浓度的TDZ替代MS中的BA，发现仅用1／50BA浓度（0．1mg／L）的TDZ处理，已相当于用BA处理所得芽数，可见它具有很强的细胞分裂素活性；但是TDZ又能显著促进乙烯形成，较低浓度时抑制莴苣的器官发生，可能此时乙烯起着主导作用。

生菜(Lactuca sativa var ro mana Hort.)下胚轴愈伤组织的诱导与植株再生

通过对生菜下胚轴的愈伤诱导和植株再生的研究 ,发现诱导愈伤组织时 ,MS培养基中加 0 .5mg/L 6 BA + 1mg/L 2 ,4 D + 0 .1mg/LNAA效果最好 ,其出愈率达 94 %;愈伤组织分化为芽时 ,在MS + 1.0mg/L 6 BA + 0 .0 5mg/L NAA中分化频率最高 ,达 10 0 %.再生苗可在 1/ 2MS+ 0 .5mg/L NAA中诱导生根成完整植株 .

Chemical composition of essential oils and in vitro antioxidant activity of fresh and dry leaves crude extracts of medicinal plant of Lactuca Sativa L.native to sultanate of Oman

Objective:To isolate and analyse the chemical composition in the essential oils and free radical scavenging activity of different crude extracts from the fresh and dry leaves of vegetable plants of Lactuca sativa L.(L.sativa).Methods:The essential oils and volatile chemical constituents were isolated from the fresh and dry leaves of L.sativa(lettuce)grown in Sultanate of Oman by hydro distillation method.The antioxidant activity of the crude extracts was carried out by well established free radical scavenging activity(DPPH)method.Results:About 20 chemical compounds of different concentration representing 83.07%and 79.88%respectively were isolated and identified by gas chromatography-mass spectroscopy in the essential oils isolated from the fresh and dry leaves asα-pinene(5.11%and 4.05%).γ-cymene(2.07%and 1.92%),thymol(11.55%and 10.73%),durenol(52.00%and 49.79%),α-terpinene(1.66%and 1.34%),thymol acetate(0.99%and 0.67%),caryophyllene(2.11%and 1.98%),spathulenol(3.09%and 2.98%).camphene(4.11%and3.65%),limonene(1.28%and 1.11%)representing these major chemical compounds.However,some other minor chemical constituents were also isolated and identified from the essential oil of lettuce including p-pinene,α-terpinolene,linalool,4-terpineol,α-terpineol,o-methylthymol,L-alloaromadendrene and viridiflorene.Conclusions:The chemical consliluents in the essential oils from the locally grown lettuce were identified in the following classes or groups of chemical compounds such as monoterpenes,sesquiterpenes volatile organic compounds and their oxygenated hydrocarbons.Therefore,the essential oils and the crude extracts from Omani vegetable species of lettuce are active candidates which would be used as antioxidant,antifungal or antimicrobial agents in new drugs preparation for therapy of infectious diseases.

Two new eudesmane sesquiterpenes from Lactuca sativa var.anagustata L

Two new eudesmane sesquiterpene lactones were isolated from the stalk of Lactuca sativa vat anagustata L and their structures were elucidated by means of spectroscopic methods, including 2D NMR （1H-1H COSY, HMBC and NOESY） as 1β-O-β-D- glucopyranosyl-4α-hydroxyl-5α, 6β, 11βH-eudesma-12, 6α-olide （1） and 1β-hydroxyl-15-O-（p-methoxyphenylacetyl）-5α, 6β, 11 βH-eudesma-3-en- 12, 6a-olide （2）.

Anxiolytic property of hydro-alcohol extract of Lactuca sativa and its effect on behavioral activities of mice

Lactuca sativa, belonging to the Asteraceae family, is a leafy vegetable known for its medicinal properties. This study aimed to understand the mechanism of Lactuca sativa extract with respect to pharmacological action. We investigated the anxiolytic effects of hydro-alcoholic extract of leaves of Lactuca sativa on mice. The behav- ioral tests performed on mice models to assess anti-anxiety properties were： open field test （OFT）, elevated plus maze test （EPM）, elevated T maze test, and marble burying test. Increased locomotor activity and time spent in the ＂open-ann＂ were observed in extract fed group. Malondialdehyde （MDA） and nitrite levels were decreased, cata- lase and glutathione levels were increased in Lactuca sativa treated mice. The data obtained in the present study suggests that the extract of Lactuca sativa can afford significant protection against anxiolytic activity.

Anxiolytic property of Lactuca sativa,effect on anxiety behaviour induced by novel food and height

Objective:To study anxiolytic property of hydro alchohol extract and to estimate polyphenols present in the extract by HPLC.Methods:To evaluate anxiolytic properly two animal models were used viz.Elevated T maze and hyponeophagia.Diazepam(1 mg/kg body wt.) served as the standard anxiolvtic agent for all the tests.The dried extract of the plant leaf in doses of 100.200 and 400 mg/kg body weight was administered orally to mice for duration of 1? or 30 days and locomotor and anxiolytic activities were performed.Polyphenols was estimated using HPLC. Results:The HPLC analysis of the polyphenols revealed the presence chlorogenic acid,vanillin, epicatechin,caffeic acid,rutin hydrate,sinapic acid,quercetin-3-rhamnoside.p-coumeric acid and quercitin.Time spent and number of entries into the open arm was improved in 30 days treated animals than that of 15 days treated groups,200 and 400 mg/kg body weight treated group showed significant results when comparing with the control group.Conclusions:Te hydro alcohol extract rich in Polyphenols and other secondary metabolites is a potent anxiolytic agent.

Construction of Lactuca sativa Plastid Transformation Vector and High-level Expression of gfp Gene in Escherichia coli

Using genomic DNA of bolting-tolerant lettuce as a template,flanking fragments of lettuce plastid rpo A gene were amplified and cloned by PCR. Targeting the sites of these two fragments,homologous recombinant fragments of exogenous gene were integrated to construct lettuce plastid expression vector p Brpo AGFP,which harbored the expression cassette Prrn-gfp-aad A-Tpsb A. The results showed that the amplified flanking fragments were 1.2 and 1.1 kb in size. After sequencing,restriction digestion,ligation and transformation,lettuce plastid expression vector containing expression cassette Prrn-gfp-aad A-Tpsb A was constructed and confirmed by SDS-PAGE electrophoresis. The results of SDS-PAGE electrophoresis indicated that gfp gene was efficiently expressed under the regulation of plasmid specific promoter Prrn and terminator Tpsb A. GFP accounted for 45. 6% of total soluble proteins; inclusion bodies accounted for 47.5 % of bacterial proteins,which reached relatively high expression levels. The construction of lettuce plastid expression vector p Brpo A-GFP laid a solid foundation for establishment of subsequent lettuce plastid transformation system and genetic improvement of lettuce using various functional genes.

Effect of Cadmium on <i>Lactuca sativa</i>Grown in Hydroponic Culture Enriched with Phosphate Fertilizer

Cadmium (Cd), one of the most toxic heavy metals added to soil after phosphate fertilizer treatment, was investigated. The effects of this metal on morphological and physiological changes of Lactuca sativa were studied in addition to its partitioning in different parts of the crop. In parallel, Lactuca sativa was allowed to grow under hydroponic conditions with modifications of the Hoagland nutrient solution. This solution was submitted to five Cd concentrations, 0, 0.093, 0.186, 0.279 and 0.372 mg Cd/L and three P concentrations, 0, 299 and 1420 mg P/L. The study showed a positive effect of phosphorus on root elongation, surface area while cadmium inhibited plant growth and sometimes the death of the plants. Cadmium was found to be accumulated in roots while zinc was preferably accumulated in the leaves and stems. The increase of performance of Lactuca sativa under hydroponic condition and Hoagland contaminated solution with cadmium was found to be better than the ones grown in Cd amended soil with or without phosphorus.

Bolting and Flowering Response of <i>Lactuca georgica</i>, a Wild Lettuce Relative, to Low Temperatures

To learn about the phenological adaptation of Lactuca georgica Grossh., a wild relative of domesticated lettuce, we studied seed sampled accessions obtained from individual plants at 19 locations throughout six regions in Armenia, and from two natural populations in Dagestan (Russian Federation) collected as bulk samples. The effects of various vernalization treatments on time to bolting, flowering and seed production time were investigated during four successive years at different growth stages of L. georgica plants. We demonstrate that low temperatures play a major role in stimulating the reproduction process of L. georgica plants. Our results would suggest that for L. georgica: 1) There is an obligatory (or nearly so) vernalization requirement;2) Plant age, vernalization duration, and genotype of original sample have a role in bolting and flowering regulation;3) Some plants behaved as typical annuals, responding to vernalization treatment at the seedling stage, but, most did not;4) Four months of vernalization could be adequate to reach bolting in plants with a developed vegetative rosette, for most—but not all—samples;5) In order to find the best solution for stimulating the reproductive process of multiple genotypes, it seems that further study should focus on about 4 - 6 months of vernalization at 4°C applied to plants of about 10 - 22 months old vegetative rosettes, with controlled post-vernalization condition;6) L. georgica germplasm could be used as a source for delayed bolting in breeding of domesticated lettuce varieties.

罗马直立生菜生长发育及营养指标对臭氧浓度升高和持续熏蒸的响应

环境臭氧(O_(3))已成为影响植物生长发育的重要生态因子。为探究地面O_(3)污染对蔬菜形态学特征及营养指标的影响,选罗马直立生菜(Lactuca sativa var.roman)为实验材料,采用开顶式气室开展熏蒸实验。实验设置4个O_(3)熏蒸浓度(NF:未过滤的环境空气;NF40:环境空气+40 nmol/mol;NF80:环境空气+80 nmol/mol;NF120:环境空气+120 nmol/mol),每个处理设置3个重复组,分析评价O_(3)污染对植物造成的可见伤害、生产量、叶片解剖学特征以及食用部位营养指标的影响。研究表明:(1)O_(3)熏蒸对生菜叶片产生不可逆的可见伤害,叶片出现浅黄色斑点和棕色斑点,且随着熏蒸时间延长,叶片出现黄化,大面积的坏死斑块,衰老加速。(2)高浓度O_(3)胁迫显著降低了生长阶段的株高(P<0.05)。与NF组相比,NF40、NF80、NF120组分别使生物量下降5.90%、14.99%、39.21%。(3)随着O_(3)熏蒸浓度升高,气孔密度增加,气孔开度减小。叶片厚度、海绵组织厚度、栅栏组织厚度与O_(3)暴露剂量AOT40呈显著负相关关系(P<0.05)。(4)高浓度O_(3)暴露使蔬菜中Ca、Na、Fe、Zn、Mg等元素含量显著降低,脂肪和蛋白质含量增加,生菜的营养指标发生改变。研究表明,罗马直立生菜对环境O_(3)污染敏感,其生长发育及营养指标在O_(3)胁迫条件下发生明显变化。目前,关于O_(3)污染对蔬菜形态学特征影响的研究较少,研究系统探讨蔬菜的叶片厚度、栅栏组织、海绵组织、气孔密度及开度等形态学指标在臭氧污染条件下的变化。蔬菜的品质是关系到“三农”问题的重要方面,研究探讨了臭氧污染对蔬菜的产量及营养指标的影响,可为O_(3)污染条件下蔬菜的生产提供科学参考。

“温控箱+蓄冷剂”包装对油麦菜贮藏品质的影响

目的探究不同包装方式对油麦菜贮藏品质的影响。方法以油麦菜为实验材料,采后分别装入泡沫箱(CK)、泡沫箱+蓄冷剂(T1)、温控箱(T2)、温控箱+蓄冷剂(T3),每隔5 d测定油麦菜的营养成分、生理生化指标和抗氧化酶活性,同时监测箱内的温度。结果CK、T1、T2、T3组温度分别为(4.06±0.07)℃、(3.61±0.05)℃、(3.72±0.04)℃、(3.49±0.03)℃,与其他处理相比,T3组温度较低,且波动范围最小;此外,T3处理组能够减缓质量损失率上升、抑制Vc氧化和叶绿素降解、延缓MDA积累、抑制PPO活性升高、维持POD、SOD、CAT活性,有效提高了油麦菜的贮藏品质,并延长了货架期。结论“温控箱+蓄冷剂”的包装方式能较好地维持油麦菜的采后贮藏品质。

微囊藻毒素-LR对生菜非结构性碳水化合物代谢的影响

【目的】研究低质量浓度微囊藻毒素-LR(MC-LR)慢性暴露对生菜(Lactuca sativa)叶片及根系非结构性碳水化合物代谢的影响,为富营养化水体在生菜灌溉中的应用提供理论指导。【方法】以散叶生菜为试验材料,采用土培试验方法,设置不同质量浓度(0(对照组),1,5,10,30μg/L)MC-LR的水溶液灌溉生菜30 d,通过分析生菜叶片及根系中可溶性糖(葡萄糖、果糖和蔗糖)及淀粉含量、蔗糖和淀粉代谢相关酶活性的变化,探讨生菜非结构性碳水化合物代谢对MC-LR慢性暴露的响应。【结果】10和30μg/L MC-LR组生菜对MC-LR的富集系数较5μg/L MC-LR组分别显著上升10.85%和17.83%(P<0.05),而对MC-LR的转运系数分别显著下降17.46%和13.85%(P<0.05)。与对照组相比,1μg/L MC-LR组生菜净光合速率显著提高了9.17%(P<0.05),叶片中果糖含量及根系中葡萄糖含量和淀粉酶(AMS)活性分别显著增加了52.71%,19.13%和37.01%(P<0.05);5,10和30μg/L MC-LR组生菜净光合速率提高,但差异不显著(P>0.05),叶片和根系中葡萄糖、果糖和蔗糖含量均显著增加(P<0.05),叶片中性转化酶(NI)活性分别显著降低了27.10%,38.01%和37.29%(P<0.05),淀粉合成酶活性分别显著增加20.92%,24.57%和30.28%(P<0.05),根系蔗糖合成酶、蔗糖磷酸合成酶(SPS)和AMS活性均显著增加(P<0.05)。【结论】1μg/L MC-LR水溶液灌溉对生菜叶片和根系中非结构性碳水化合物的分布和代谢影响较弱;而5~30μg/L MC-LR水溶液灌溉通过促进生菜根系淀粉分解和蔗糖代谢活性,维持体内较高浓度的可溶性糖,从而提高生菜的抗逆性。

不同营养液EC值对叶用莴苣生长及营养品质的影响

为明确营养液EC值对不同叶用莴苣品种生长和营养品质的影响,本研究采用单因素试验设计,设置3个不同营养液EC值(1.6、2.0、2.4 mS/cm),培养2种叶用莴苣,并测定其植株的农艺性状、光合指标及营养品质。结果表明:不同叶用莴苣品种对营养液EC值相应不同,当营养液EC值为1.6 mS/cm时,有利于紫霞品种的生长,表现为冠幅较大、最大叶宽较宽、光合指标较高、干物质及维生素C含量较高;当营养液EC值为2.0 mS/cm时,则有利于玛丽娜品种的生长,但营养指标较低。说明,不同叶用莴苣品种的农艺性状、光合指标及营养品质对营养液EC值反应差异较大。在叶用莴苣种植过程中,应根据叶用莴苣品种、生育期等适当调节营养液EC值,避免盲目提高营养液EC值,造成不必要的浪费。

超高效液相色谱-串联质谱法测定生菜中氟吡菌酰胺及其代谢物残留量

目的建立超高效液相色谱-串联质谱法测定生菜中氟吡菌酰胺及其代谢物2-(三氟甲基)苯甲酰胺的方法。方法采用QuEChERS技术,用乙腈对生菜样品进行萃取,C_(18)净化剂净化后,用含0.1%甲酸的乙酸铵溶液-乙腈在BEH C_(18)色谱柱上进行洗脱分离,质谱检测器测定。结果氟吡菌酰胺和2-(三氟甲基)苯甲酰胺在1.0~50.0 ng/mL质量浓度范围内,质量浓度与其质谱响应强度之间呈线性关系,相关系数不小于0.9996;检出限为0.25μg/kg,定量限为0.10μg/kg;回收率平均值在94.6%~97.2%,相对标准偏差为1.3%~4.5%。结论所建超高效液相色谱-串联质谱法灵敏度高、精密度好、准确度高、前处理简便,可为生菜农药残留监测及氟吡菌酰胺农药残留消解动态分析提供技术支撑。

Light-Emitting Diodes (LEDs) for Miniature Hydroponic Lettuce

There is growing concern about food safety, environmental impact, and efficient energy usage in agricultural production systems. Producing lettuce under artificial lighting could be a solution addressing these concerns. Light-emitting diodes (LEDs) offer the advantages of a narrow light spectrum, low power consumption, and little heat production. The objective of this study was to determine the effects of different light sources on the growth of miniature “Tom Thumb” butterhead lettuce in a non-circulating hydroponic system. Lettuce seedlings, started in Oasis Horticubes, were transferred to net pots in containers with a hydroponic nutrient solution. The lettuce was grown in a lab under three light treatments—blue LEDs, red LEDs, and fluorescent lights. At the end of the study, fluorescent lights resulted in greater root dry weight than blue LEDs and red LEDs. Total plant dry weight under fluorescent lights was greater than under red LEDs. There were no significant differences in shoot dry weight and plant height among the treatments. Percent partitioning of dry weight to shoots was greatest with red LEDs, followed by blue LEDS, and fluorescent lights. Percent partitioning of dry weight to roots was greatest with fluorescent lights, followed by blue LEDS, and red LEDs. Leaf chlorophyll content was greater under blue LEDs and fluorescent lights than red LEDs. The pH of the nutrient solution of the blue LED and the fluorescent light treatments were greater than the red LED treatment. Electrical conductivity of the nutrient solution of the fluorescent light treatment was greater than the blue LED treatment and the red LED treatment. In conclusion, LEDs could provide an alternative lighting source for miniature lettuce production.

Lettuce production according to different sources of organic matter and soil cover

Lettuce (Lactuca sativa L.) is one of the leading vegetables produced by farmers in the Itabaiana region, and thus it is important to study means of sustainable management for the crop. The objective of this work was to evaluate the behavior of lettuce with different sources of organic matter and soil cover. Therefore, it was chosen to cultivate Veronica. The experiment was carried out in the experimental field plot of Project Small Farmer—Great Entrepreneur in the municipality of Itabaiana-SE, in 2010. The design was a randomized block design with four replications, with treatments consisting of five sources of organic matter (organic compost, chicken manure, cattle manure, sheep manure, and castor bean) and a control (no fertilizer), all with and without mulch, totaling 12 treatments. We evaluated the characteristics of plant diameter, plant height, fresh and dry root and shoot matter. We also evaluated the influence on the temperature and soil water tension. All productivity characteristics valuated showed the significant interaction between the type of fertilizer and the mulch, except for root dry weight, where only organic manure was a significant factor. When soil mulch was used, the best source of organic matter for growing lettuce was chicken manure, and in the impossibility of using this cover, we recommend the use of organic compost as a source of organic matter, as it showed the best result in the absence of coverage. The cover age also showed good results in relation to a temperature that promoted lower soil water tensions.