A novel role for proline in plant floral nectars

Plants offer metabolically rich floral nectar to attract visiting pollinators. The composition of nectar includes not only sugars, but also amino acids. We have examined the amino acid content of the nectar of ornamental tobacco and found that it is extremely rich (2 mM) in proline. Because insect pollinators preferentially utilize proline during the initial phases of insect flight and can reportedly taste proline, we determined whether honeybees showed a preference for synthetic nectars rich in proline. We therefore established an insect preference test and found that honeybees indeed prefer nectars rich in the amino acid proline. To determine whether this was a general phenomenon, we also examined the nectars of two insect-pollinated wild perennial species of soybean. These species also showed high levels of proline in their nectars demonstrating that plants often produce proline-rich floral nectar. Because insects such as honeybees prefer proline-rich nectars, we hypothesize that some plants offer proline-rich nectars as a mechanism to attract visiting pollinators.     

On the evolutionary significance of the size and planarity of the proline ring

Proline is a proteinogenic amino acid in which the side chain forms a ring, the pyrrolidine ring. This is a five-membered ring made up of four carbons and one nitrogen. Here, we study the evolutionary significance of this ring size. It is shown that the size of the pyrrolidine ring has the advantage of being nearly planar and strain-free, based on a general mathematical assertion saying that the angular sum of a polygon is maximum if it is planar and convex. We also provide a sketch of the proof to this assertion. The optimality of the ring size of proline can be derived from a triangle inequality for angles. Quasi-planarity is physiologically significant because it allows an easier and evolutionarily old type of fit into binding grooves of proteins with which proline-rich proteins interact. Finally, we present a comparison with other planar, nearly planar and non-planar biomolecules such as neurotransmitters, hormones and toxins, involving, for example, aromatic rings, cyclopentanone and 1,3-dioxole.     

球果蔊菜脯氨酸的积累及与Cd耐性的关系

采用盆栽方法,以风花菜(Rorippa islandica)为对照植物,研究Cd超积累植物球果蔊菜[Rorippa globosa (Turcz.) Thell.]脯氨酸的积累、丙二醛含量、生物量及叶绿素含量的变化,及其与Cd生物积累的关系.结果显示,Cd处理能明显促进2种植物体内脯氨酸的积累,当土壤中Cd浓度≤25μg/g时,球果蔊菜叶片脯氨酸的积累效应尤为显著;此时叶片生物量、叶绿素及丙二醛含量与对照相比均无显著差异,表明其叶片脯氨酸的积累在一定程度上可缓解Cd胁迫造成的氧化损伤.相关分析表明,球果蔊菜根系脯氨酸可指示球果蔊菜根系中Cd的积累.     

水分胁迫环境对管花蒲公英体内POD活性与游离脯氨酸含量的影响

本实验选取管花蒲公英种子在实验室条件下种植,当幼苗长到5-6片真叶时进行水分胁迫处理,结果表明水分协迫组植株比正常植株的POD活性和脯氨酸含量高,而且随着胁迫时间的增加,POD活性和脯氨酸含量也随之增加.     

二氧化硫暴露对谷子幼苗气孔运动、脯氨酸代谢和抗氧化酶系统的影响

二氧化硫(SO_2)是一种有毒的大气污染物,主要经气孔进入植物体内.目前对于SO_2毒性的研究多集中在氧化损伤方面,关于SO_2对植物脯氨酸代谢的影响及相关分子机制的研究还很少.本文以谷子幼苗为材料,研究了不同浓度SO_2气体暴露对叶片气孔运动、脯氨酸代谢和抗氧化酶系统的影响.结果显示,10 mg·m~(-3) SO_2熏气对谷子幼苗的叶片形态、相对含水量、气孔开度、脯氨酸含量及抗氧化酶活性均无明显影响.30 mg·m~(-3) SO_2暴露24～72 h后,叶片出现明显的受损症状,相对含水量降低,叶面气孔开度减小;30 mg·m~(-3) SO_2熏气导致叶中脯氨酸含量显著增加,脯氨酸脱氢酶(PDH)活性明显升高.同时,长时间的SO_2胁迫可诱导SiPDH基因表达上调,而脯氨酸合成相关基因SiP5CS、SiP5CR表达受到明显抑制.此外,谷子幼苗暴露于30 mg·m~(-3) SO_2时,叶中超氧阴离子(O■)产生速率与对照相比显著提高,诱导超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性增强,从而将过氧化氢(H_2O_2)含量维持在正常水平.以上结果表明,SO_2对谷子的毒性效应具有浓度依赖性.高浓度SO_2暴露下,谷子能够通过控制气孔开放、调节脯氨酸代谢和抗氧化酶活性等过程来适应SO_2胁迫.     

地下水溶质反常运移的分数阶对流扩散模型研究进展

地下水溶质在非均质多孔介质中的扩散过程并不总是遵循Fick定律,因此称为反常扩散或反常运移,其本质上是非马尔可夫非局域性过程.分数阶对流扩散模型可以对含水层中溶质的这种运移进行充分而准确的描述.本文在阐明多孔介质溶质反常运移基本问题及其动力学机理基础上,综述了三类分数阶对流扩散模型,即空间分数阶对流扩散模型、时间分数阶对流扩散模型和分布式分数阶对流扩散模型,并详细讨论了分数阶对流扩散模型在地下水溶质反常运移领域的应用前景和挑战.     

Phytotoxicity of cadmium on protein, proline and antioxidant enzyme activities in growing Arachis hypogaea L. seedlings

Phytotoxicity of cadmium on growing Arachis hypogaea L. seedlings was studied. Seeds were exposed to 25, 50, and 100 μmol/L CdCl2 concentrations, for a period of 10, 15, 20 and 25 d. The extent of damage to chlorophyll, protein, proline, nitrate and nitrite reductase, antioxidant enzyme activity in leaves and roots were evaluated after 10 d of cadmium stress. The higher concentration of cadmium （100 μmol/L） resulted （leaves and roots） total chlorophyll 91.01%, protein 79.51%, 83.61%, nitrate reductase 79.39%, 80.72% and nitrite reductase 77.07%, 75.88% activity decreased with increase in cadmium concentrations and exposure periods. Cadmium caused significant changes in the activity of antioxidative enzymes. Contrastingly Cd treated plant tissues showed an increase in proline 159.87%, 239.6%, gluthion reductase （GR） 337.72%, 306.14%, superoxide disumutase （SOD） 688.56%, 381.72%, ascorbate peroxidase （APX） 226.47%, 252.14%, peroxidase （POD） 72.19%, 60.29% and catalase （CAT） 228.96%, 214.74% as compared to control. Cadmium stress caused a significant increase in the rate of SOD activity in leaves and roots of plant species. Results show the crop A. hypogaea is highly sensitive even at very low cadmium concentrations.     

黑炭腐殖酸复合物对泰乐菌素的吸附特性

以泰乐菌素作为目标有机污染物,系统研究了不同来源的纳米黑炭与腐殖酸的复合物对泰乐菌素的吸附特性和机制.结果表明：黑炭与腐殖酸复合后其对泰乐菌素的吸附明显增强;吸附在24h可完全达到平衡,吸附动力学可以用二级动力学较好的拟合;且线性吸附模型和Freundlich吸附模型可以较好的拟合吸附等温线;黑炭与腐殖酸复合后其对泰乐菌素的吸附受溶液pH值和离子强度的影响.吸附机制主要以疏水性分配、氢键作用和离子交换为主.     

SBAR中好氧污泥颗粒化及其特性

采用气升式内循环间歇反应器对好氧污泥颗粒化的过程进行了研究,考察了不同水力循环时间下好氧污泥颗粒化过程及其特性,并且对反应器中形成的好氧颗粒污泥内部菌群形态进行了描述.结果表明,不同水力循环时间对好氧颗粒污泥生长特性产生了很大的影响,在较短水力循环时间下,颗粒污泥粒径增长速度快,形成的颗粒粒径多数在 1.0～2.0mm 之间,并且 VSS含量达 92.08%,强度也较高,而在较长水力循环时间中形成的颗粒粒径在 0.5～1.0mm 之间、VSS 含量在 83.92%,污泥强度下降.     

生物膜—膜生物反应器脱氮除磷性能

在膜生物反应器中投加聚乙烯悬浮填料,考察生物膜—膜生物反应器对生活污水中污染物质去除效果.结果表明,投加悬浮填料使膜生物反应器去除有机污染物质的能力得到增强,总氮、总磷的平均去除率由45.5%和47.2%分别增至57.4%和71.8%.投加悬浮填料还可以延缓膜污染,膜生物反应器中膜丝比流量在试验结束时为0.1L/(hkPa),而未投加悬浮填料的膜生物反应器中膜丝比流量降至0.036L/(hkPa).     

The influence of sewage sludge properties on sludge-borne metal availability

With the advent of more stringent controls on wastewater treatment, sewage sludge production in Europe and many parts of the world is increasing. With this increase comes the problem of sludge disposal, and recycling to land arguably offers an economically and environmentally sustainable option. However, a major limitation of sewage sludge reuse is the potential release of heavy metals from the sludge and heavy metal accumulation to toxic levels in topsoils. The properties of the sludge play a crucial role in determining the initial release and subsequent availability of heavy metals in amended soils. Bioavailable forms of heavy metals in recently amended soils are most likely to be those that are bioavailable in the sewage sludge. In this paper, published research on the importance of sewage sludge characteristics on metal release and bioavailability will be reviewed and contrasted with original research. A selection of sludges from around Australia has been collected for this purpose. Through the use of incubation studies, isotope dilution techniques, ion-selective electrode measurements and ¹³C-NMR spectroscopy, the importance of a range of sludge properties on heavy metal behaviour in sludges and sludge-amended soils is addressed.     

脯氨酸掺杂g-C3N4纳米片的制备及其对RhB的降解

通过简单的水热及煅烧方法制备了脯氨酸掺杂的g-C₃N₄纳米片,借助FTIR、XRD、SEM、BET、XPS、UV-vis DRS、PL、电化学工作站等手段对所制备的光催化剂进行结构、形貌、组成及光电性能表征分析.结果表明,脯氨酸的加入可以自主剥离前驱体,制成纳米片状的g-C₃N₄,增加催化剂的比表面积.此外脯氨酸的引入可以调节催化剂的能带结构,增加可见光吸收,提高光生载流子分离率.在模拟可见光照射下,考察其对罗丹明B (RhB)的光催化降解性能获得了最优掺杂条件.1%脯氨酸掺杂(PCN-1%)的催化剂经过60min可见光照射即可降解99%以上的污染物.降解速率得到显著提升,PCN-1%对RhB的降解速度(0.0271min^-1)达到传统体相氮化碳(BCN)降解速率(0.0027min^-1)的10.04倍,显著提高了g-C₃N₄的光催化能力.     

河道淤泥的有效利用方式及其物性探讨

对河道淤泥再生资源化利用的可能性及方式进行了探讨。在室内试验的基础上，评价了处理后的河道淤泥作为填上材料使用时的基本工程性质，为促进河道淤泥的再生资源化利用和保护环境提供了必要的依据。