Self-propulsion of dew drops on lotus leaves: a potential mechanism for self cleaning

This study shows that condensation on the hierarchically structured lotus leaf can facilitate self-propulsion of water droplets off the surface. Droplets on leaves inclined at high angles can be completely removed from the surface by self-propulsion with the assistance of gravity. Due to the small size of mobile droplets, light breezes may also fully remove the propelled droplets, which are typically projected beyond the boundary layer of the leaf cuticle. Moreover the self-propelled droplets/condensate were able to remove contaminants (eg silica particles) from the leaf surface. The biological significance of this process may be associated with maintaining a healthy cuticle surface when the action of rain to clean the surface via the lotus effect is not possible (due to no precipitation). Indeed, the native lotus plants in this study were located in a region with extended time periods (several months) without rain. Thus, dew formation on the leaf may provide an alternative self-cleaning mechanism during times of drought and optimise the functional efficiency of the leaf surface as well as protecting the surface from long term exposure to pathogens such as bacteria and fungi.     

Anisotropism of the Non-Smooth Surface of Butterfly Wing

Twenty-nine species of butterflies were collected for observation and determination of the wing surfaces using a ScanningElectron Microscope(SEM).Butterfly wing surface displays structural anisotropism in micro-,submicro- and nano-scales.Thescales on butterfly wing surface arrange like overlapping roof tiles.There are submicrometric vertical gibbosities,horizontallinks,and nano-protuberances on the scales.First-incline-then-drip method and first-drip-then-incline method were used tomeasure the Sliding Angle(SA)of droplet on butterfly wing surface by an optical Contact Angle(CA)measuring system.Relatively smaller sliding angles indicate that the butterfly wing surface has fine self-cleaning property.Significantly differentSAs in various directions indicate the anisotropic self-cleaning property of butterfly wing surface.The SAs on the butterfly wingsurface without scales are remarkably larger than those with scales,which proves the crucial role of scales in determining theself-cleaning property.Butterfly wing surface is a template for design and fabrication ofbiomimetic materials and self-cleaningsubstrates.This work may offer insights into how to design directional self-cleaning coatings and anisotropic wetting surface.     

Impact of Drops on Non-wetting Biomimetic Surfaces

We have carried out an experimental study of liquid drop impact on superhydrophobic substrates covered by a carpet ofchemically coated nano-wires.The micro-structure of the surface is similar to some biological ones(Lotus leaf for example).Inthis situation the contact angle can then be considered as equal to 180 degrees,with no hysteresis.Due to its initial inertia,thedrop experiences a flattening phase after it hits the surface,taking the shape of a pancake.Once it reaches its maximal lateralextension,the drop begins to retract and bounces back.We have extracted the lateral extension of the drop,and we propose amodel that explains the trend.We find a limit initial velocity beyond which the drop protrudes into the nano-wire carpet.Wediscuss the relevance of practical issues in terms of self-cleaning surfaces or spray-cooling.     

Trypsin-enabled construction of anti-fouling and self-cleaning polyethersulfone membrane

Constructing anti-fouling and self-cleaning membrane surfaces based on covalent attachment of trypsin on poly(methacrylic acid)-graft-polyethersulfone (PMAA-g-PES) membrane was reported. The carboxylic acid groups enriched on asymmetric PMAA-g-PES membrane surface were activated with 1-ethyl-(3-3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) and employed as chemical anchors for the conjugation with amino groups of trypsin. Activity assays showed that such chemically immobilized trypsin was much more active and stable than that of the physically adsorbed counterpart. Trypsin covalently attached on membrane surface could substantially resist protein fouling in dynamic flow process. The considerable enhancement of protein solution permeation flux was observed as a consequence of rapid enzymatic degradation of protein deposited onto membrane surface. The permeation flux of the membrane could be recovered upon simple hydraulic flush after protein filtration, suggesting superior self-cleaning property. After multi-cycle BSA filtration over 15-day period, the active self-cleaning membrane maintained more than 95.0% of its initial flux.     

Genome of the long-living sacred lotus (Nelumbo nucifera Gaertn.)

Background

Sacred lotus is a basal eudicot with agricultural, medicinal, cultural and religious importance. It was domesticated in Asia about 7,000 years ago, and cultivated for its rhizomes and seeds as a food crop. It is particularly noted for its 1,300-year seed longevity and exceptional water repellency, known as the lotus effect. The latter property is due to the nanoscopic closely packed protuberances of its self-cleaning leaf surface, which have been adapted for the manufacture of a self-cleaning industrial paint, Lotusan.

Results

The genome of the China Antique variety of the sacred lotus was sequenced with Illumina and 454 technologies, at respective depths of 101× and 5.2×. The final assembly has a contig N50 of 38.8 kbp and a scaffold N50 of 3.4 Mbp, and covers 86.5% of the estimated 929 Mbp total genome size. The genome notably lacks the paleo-triplication observed in other eudicots, but reveals a lineage-specific duplication. The genome has evidence of slow evolution, with a 30% slower nucleotide mutation rate than observed in grape. Comparisons of the available sequenced genomes suggest a minimum gene set for vascular plants of 4,223 genes. Strikingly, the sacred lotus has 16 COG2132 multi-copper oxidase family proteins with root-specific expression; these are involved in root meristem phosphate starvation, reflecting adaptation to limited nutrient availability in an aquatic environment.

Conclusions

The slow nucleotide substitution rate makes the sacred lotus a better resource than the current standard, grape, for reconstructing the pan-eudicot genome, and should therefore accelerate comparative analysis between eudicots and monocots.     

Ultrastructure of rabbit tracheal epithelium after saline lavage of the airways

In experiment the effect of saline lavage on the ultrastructure of the tracheal epithelium was investigated. Immediately after this procedure the trachea was lined with markedly altered pseudostratified columnar epithelium with remnants of the ciliary border. The intercellular spaces were markedly dilated, but the apical junctional complexes were left intact. 99% of the goblet cells were exhausted degenerated and were gradually expelled from the epithelium. Damage to the ciliated cells was not so generalized but some of them displayed signs of vacuolar degeneration. The ciliary border was severely impaired with only 1.5 kinocilia/microns 2, but the majority of remaining cilia were intact. Compared with controls there was only mild, but significant increase in the number of degenerating and malformed cilia. Morphological signs of impaired self-cleaning ability of the epithelium were not noticed.     

菲氏叶猴与黑叶猴的下颌骨

本文对15只菲氏叶猴和8只黑叶猴成年下颌骨作了功能形态学研究。在21项所分析的变量中,两种之间有4项达到显著性差异水平,而10项达到非常显著的差异水平。从所分析的结构看来,菲氏时猴下臼齿及门齿的面积大于黑叶猴,而黑叶猴的咬肌附着部分(支高、颌高,支宽及髁头长)大于菲氏叶猴。这表现了黑叶猴比菲氏叶猴具更强的咀嚼能力。因而,可以推测在食物成分中,黑叶猴食坚果的比例要大于菲氏叶猴。     

Biomimetic Superhydrophobic Surfaces with Transition Metals and Their Oxides: A Review

Transition metals and their oxide materials have been widely employed to fabricate superhydrophobic surfaces,not onlybecause of their surface topography with controllable microstructures leading to water-repellence,diverse adhesion even tunable wettability,but also due to a variety of special properties like optical performance,magnetism,anti-bacterial,transparency and so on.At the meantime,biomimetic superhydrophobic surfaces have attracted great interest from fabricating hierarchical micro-/nano-structures inspired by nature to imitate creature's properties and many potential applications,including self-cleaning,antifogging,antireflection,low drag and great stability and durability.In this review,natural surfaces and biomimetic materials with special wettability are introduced by classification according to the similar microstructure of morphology,like array structure,sheet overlapped structure,high density hairs and seta shaped structure.Not only do we exhibit their special performances,but also try to find out the true reasons behind the phenomenon.Then,the recent progress of a series of superhydrophobic transition mental and their oxide materials,including TiO2,ZnO,Fe3O4,CuO,Ag,Au and so on,is presented with a focus on fabricating methods,microstructures,wettability,and other properties.As followed,these superhydro-phobic surfaces can be applied in many fields,such as oil/water separation,self-cleaning,photo-controlled reversible wettability,surface-enhanced Raman scattering,antibacterial,anticorrosion,and synthesis of various applications.However,few of them have been applied in practical life.Hence,we discuss the remaining challenges at present and the development tendency in future at the end of this article.This review aims to present recent development of transition metals and their oxides applied in biomimetic superhydrophobic surfaces about fabrication,microstructure,water repellence,various properties,and potential applications.     

Infection of ryegrass plants with ryegrass mosaic virus decreases numbers of the mite vector

A single spray of tridemorph on 1 June almost doubled leaf area index of Zephyr barley during much of the second half of June. Increases in leaf area duration before ear emergence seemed important in these plots, because they yielded much better than plots sprayed on 11 June although differing little from them in leaf area duration after ear emergence.     

根据叶表皮微形态特征试论披碱草属（禾本科）中小颖组、宽颖组和长颖组间的系统关系

观察了披碱草属中小颖组、宽颖组和长颖组主要代表种的叶表皮形态学特征,总结了3组植物叶表皮结构的异同,探讨了叶表皮特征的分类学意义。同时,根据3组植物叶表皮性状的演化趋势,分析了各组的演化关系和系统位置。结果表明,小颖组最原始,宽颖组较进化,长颖组最高级;小颖组可能直接派生了较进化的宽颖组,并在宽颖组的基础上进而产生了最高级的长颖组。小颖组、宽颖组和长颖组的这一系统关系与利用外部形态特征所获得的演化趋势基本一致。     

The dream of staying clean: Lotus and biomimetic surfaces

The Lotus has been the symbol of purity for thousands of years; contaminations and pathogens are washed off the surfaces of Lotus and some other plants with rain or even dew. After the introduction of scanning electron microscopy, we were able to resolve the mechanism behind this phenomenon. It took some further decades before in-depth studies on self-cleaning with plants were conducted and the effect could be understood in detail. We identified extreme water-repellency ('superhydrophobicity'), characterized by very high contact angles and low sliding angles, as the prerequisite for self-cleaning properties. We could show that the combination of two factors is necessary for obtaining a high degree of water-repellency: (1) low energy surfaces being hydrophobic and (2) surface structures that significantly increase hydrophobicity. It is suggested that this mechanism plays an important role in the protection of plants against pathogens. Our technological application of this effect has resulted in the development of successful, eco-friendly and sustainable industrial products. Another interesting property was found with superhydrophobic surfaces of certain aquatic and semi-aquatic plants and animals: here a layer of air under water is retained. We present a new approach of using this feature for creating structured, air-retaining surfaces for technical underwater applications. It is proposed that such surfaces can reduce significantly the drag of large ships. We conclude that basic biological research is of particular importance for true innovation. Our research on superhydrophobic self-cleaning biological surfaces and the development of similar engineered materials suggests that biomimicry is a matter of multi-stage processes rather than a simple copying of biological developments.     

Cytokinin-dependent expression of the ARR5::GUS construct during transgenic arabidopsis growth

Growth and glucuronidase (GUS) activity were followed in the cotyledons and rosette leaves of Arabidopsis thaliana (L.) Heynh (ecotype Wassilewskija) plants transformed with the GUS gene under the control of the cytokinin-dependent promoter of the ARR5 gene. The presence of active cytokinins in plant tissues was assessed from GUS activity. Plants were grown for three weeks on the nitrate-or ammonium-containing nutrient medium. In plants grown on ammonium nutrition, cotyledon and leaf growth was substantially suppressed as compared with plants feeding with nitrates. In correspondence with this growth inhibition, GUS activity was markedly lower in plant leaves grown on the ammonium-containing medium. This indicated a reduction in these leaves of active cytokinin forms capable of activation of the promoter for the ARR5 gene. On both nitrogen sources, GUS activity increased during leaf growth and dropped sharply after growth ceasing. This indicated that leaf growth depended on the cytokinin content in them. High GUS activity was detected in petioles and leaf conductive system, indicating leaf providing with cytokinins along the conductive vessels. A sharp drop in the GUS activity after leaf growth stoppage coincided in time with GUS activation in the leaf positioned above this leaf. This indicated possible cytokinin redistribution in the plant; its content could be a limiting factor for leaf growth. A higher growth rate in plants on nitrate nitrogen nutrition and corresponding high GUS activity in them are discussed in terms of cytokinin signaling role in leaf growth regulation mediated by nitrate.     

Phase behavior of a model bilayer membrane with coupled leaves

We discuss the thermodynamic behavior of a bilayer composed of two coupled leaves and derive the Gibbs Phase Rule for such a system. A simple phenomenological model of such a system is considered in which the state of the bilayer is specified by the relative number of ordering lipids in the outer leaf, and in the inner leaf. Two cases are treated. In the first, both inner and outer leaves could undergo phase separation when uncoupled from one another. The bilayer can exist in four different phases, and can exhibit three-phase coexistence. In the second case, an outer layer which can undergo phase separation by itself is coupled to an inner leaf which cannot. We find that when the coupling is weak, the bilayer can exist in only two phases, one in which the outer layer is rich in ordering lipids and the inner leaf is somewhat richer in them than when uncoupled, and another in which the outer layer is poor in ordering lipids and the inner leaf is poorer in them than when uncoupled. Increasing the coupling increases the effect on the inner leaf composition due to small changes in those of the outer leaf. For sufficiently large coupling, a phase transition occurs and the bilayer exhibits four phases as in the first case considered. Our results are in accord with several observations made recently.     

The morphology of a potato leaf such as that of Solarium andigenum Juz. et Buk.

The morphology of a potato with a dissected leaf, such as that of Solanum andigenum Juz. et Buk., is considered, and a terminology for leaf dissection is proposed. Summary comparison of the principal characters of the leaves of various S. andigenum varieties showed that the majority of them have a strong degree of dissection, a considerable distance between the adjacent leaf lobes and mostly ovate lobes with long rachidules.     

Abnormal germling development by brown rust and powdery mildew on cer barley mutants

The barley leaf rust fungus forms appressoria over host leaf stomata and penetrates via the stomatal pore. High levels of avoidance to leaf rust fungi have been described in some wild accessions of Hordeum species where a prominent wax layer on the stomata inhibits triggering of fungal appressorium differentiation. Leaf rust avoidance has not yet been found in H. vulgare. Since cuticular leaf waxes are implicated in the avoidance trait, we screened 27 eceriferum (cer) mutant lines of H. vulgare for avoidance to barley leaf rust. These mutations affect leaf waxes. Reduction in numbers of germ tubes forming appressoria over stomata was found in some lines, but the greatest reduction (ca 30%) was less than previously found in wild barley spp. or in an accession of H. chilense used here as a check. In one line (cer-zh654), avoidance was due to a combination of factors. Firstly, fewer germ tubes oriented towards stomata and so failed to contact them. Secondly, some germ tubes that encountered stomata did not form appressoria but over-grew them. In this line, therefore, the fungus tended to fail both to locate and to respond to stomata. The appressoria of barley powdery mildew form on leaf epidermal cells that they penetrate directly. On certain cer lines, a proportion of germlings of the barley powdery mildew fungus developed abnormally, suggesting that germlings failed to recognise and/or respond to the leaf surface waxes on these mutants.     

Automatically diagnosing leaf scorching and disease symptoms in trees/shrubs by using RGB image computation with a common statistical algorithm

Better computation and auto-identification of plant and tree characteristics is usually based on the direct use of knowledge about them. With the background of our previous study about manual image measurement of leaf scorch symptoms, we try to automatically diagnose leaf scorching and the inward spread of leaf disease symptoms by using RGB image computation to increase the mechanical utilization and improve the identification efficiency in the future. The special characteristics of the symptoms made them easy to identify automatically. In the process of performing the computation, common statistical algorithms, such as quadratic functional regression and variance analysis, were used to obtain proper parameters for the final discrimination of the symptoms. By using our program, more than 80% of sample cases were correctly classified.     

Do leaf shelters always protect caterpillars from invertebrate predators?

Abstract 1. All larval instars of Epargyreus clarus , the silver-spotted skipper, construct and inhabit leaf shelters that are presumed to protect them from predator attack.
2. Shelters effectively protected the larvae against foraging Crematogaster opuntiae ants and naive Polistes spp. wasps in laboratory tests, but did not protect them from predators, largely vespid wasps, present in the field.
3. A range of factors, including type of predator, learning ability, and experience level, may determine the effectiveness of leaf shelters as protection from predators.     

北京市11种园林植物滞留大气颗粒物能力研究

测定了北京市11种园林植物叶面颗粒物附着密度,利用环境扫描电镜观察比较了各测试树种叶表面微形态,测量统计了滞留颗粒物的粒径分布.结果表明,植物主要通过叶片上表面滞留大气颗粒物,上表面滞留的大气颗粒物数量约为下表面的5倍;叶片上表面滞留大气颗粒物能力由高到低的微形态结构依次是沟槽>叶脉＋小室 >小室>条状突起,并且结构越密集、深浅差别越大,越有利于滞留大气颗粒物;测试树种叶片上、下表面PM_2.5和PM₁₀平均百分含量分别为66.7％和98.3％与 43.4％和92.9％.     

北京东灵山不同坡位辽东栎(Quercus liaotungensis)叶属性的比较

植物在山地环境中生存不仅受到海拔等大尺度地形因子的影响,坡位等小尺度地形因子也会对植物产生影响.不同坡位上光照、温度、土壤养分和水分等均会影响到植物的资源利用策略.为比较不同坡位对辽东栎资源利用策略的影响,在北京东灵山海拔1000～1800 m的辽东栎分布范围内针对比叶面积、叶氮含量和叶干物质含量3个重要的叶属性进行了研究.ANOVA统计分析发现,地形和土壤养分及水分等环境因子在不同坡位上出现变化,但只有土壤有机质含量有显著差异.在叶属性中,干物质含量在上坡位最高,下坡位最低,在坡位间差异极显著.比叶面积与叶干物质含量在不同坡位间均成反比关系,在上坡位比叶面积变化一定的情况下,叶干物质含量的变化幅度最小;而比叶面积与叶氮含量仅在上坡位成反比关系.这些结果说明坡位对辽东栎的叶属性有一定的影响,尤其是上坡位的影响最大.