The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden

River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S. myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed.     

Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite

The carbon nanotubes–chitosan (CNTs–CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs–CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and O₂ with K_m values of 19.86 μM, 9.43 μM, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and O₂), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction. It can be extended to immobilize other enzymes and biomolecules, which will greatly facilitate the development of biosensors, biofuel cells, and other bioelectrochemical devices.     

Syntheses of fully sulfonated polyaniline nano-networks and its application to the direct electrochemistry of cytochrome c

Fully sulfonated polyaniline nano-particles, nano-fibrils and nano-networks have been achieved for the first time by electrochemical homopolymerization of orthanilic acid using a three-step electrochemical deposition procedure in a mixed solvent of acetonitrile (ACN) and water. The diameter of the uniform nano-particles is about 60 nm, and the nano-fibrils can be organized in two-dimensional (2D) or three-dimensional (3D) non-periodic networks with good electrical contact. Average distance between contacts is about 850 and 600nm for a 2D and 3D system, respectively. The details of the poly(orthanilic acid) (POA) nano-structure were examined with a field emission scanning electron microscope (SEM). The structure and properties of POA were characterized with FTIR, UV-vis and electrochemical methods. The 3D POA nano-networks coated platinum electrode gave a direct electrochemical behavior of horse heart cytochrome c (Cyt c) immobilized on this electrode surface, a pair of well-defined redox waves with formal potential (E( degrees ')) of -0.032 V (versus Ag/AgCl) was achieved. The interaction between Cyt c and POA makes the formal potential shift negatively compared to that of Cyt c in solution. Spectrophotometric and electrochemical methods were used to investigate the interaction of Cyt c with POA. The immobilized Cyt c in the nano-networks POA film maintained its activity, showing a surface-controlled electrode process with the electron transfer rate constant (k(s)) of 21s(-1) and a of 0.53, and could be used for the electrocatalytic reduction of hydrogen peroxide. The quantitative determination of Cyt c by differential pulse voltammetry (DPV) using the fully sulfonated 3D POA nano-networks film coated platinum electrode was also studied.     

Production of hyperthermostable GH10 xylanase Xyl10B from Thermotoga maritima in transplastomic plants enables complete hydrolysis of methylglucuronoxylan to fermentable sugars for biofuel production

Overcoming the recalcitrance in lignocellulosic biomass for efficient hydrolysis of the polysaccharides cellulose and hemicellulose to fermentable sugars is a research priority for the transition from a fossilfuel-based economy to a renewable carbohydrate economy. Methylglucuronoxylans (MeGXn) are the major components of hemicellulose in woody biofuel crops. Here, we describe efficient production of the GH10 xylanase Xyl10B from Thermotoga maritima in transplastomic plants and demonstrate exceptional stability and catalytic activities of the in planta produced enzyme. Fully expanded leaves from homotransplastomic plants contained enzymatically active Xyl10B at a level of 11-15% of their total soluble protein. Transplastomic plants and their seed progeny were morphologically indistinguishable from non-transgenic plants. Catalytic activity of in planta produced Xyl10B was detected with poplar, sweetgum and birchwood xylan substrates following incubation between 40 and 90 °C and was also stable in dry and stored leaves. Optimal yields of Xyl10B were obtained from dry leaves if crude protein extraction was performed at 85 °C. The transplastomic plant derived Xyl10B showed exceptional catalytic activity and enabled the complete hydrolysis of MeGXn to fermentable sugars with the help of a single accessory enzyme (α-glucuronidase) as revealed by the sugar release assay. Even without this accessory enzyme, the majority of MeGXn was hydrolyzed by the transplastomic plant-derived Xyl10B to fermentable xylose and xylobiose.     

外源水杨酸对镉胁迫甜瓜幼苗生长与光合气体交换和叶绿素荧光特性的影响

以甜瓜品种‘哈密绿’为试验材料,采用基质栽培方式,研究了10~200μmol·L-1外源水杨酸(SA)对镉胁迫(100mg·L-1 Cd2+)下甜瓜幼苗生长、叶绿素含量、光合气体交换参数和叶绿素荧光参数的影响,以探讨外源SA调控Cd2+胁迫伤害的可行性。结果显示:Cd2+胁迫能显著影响甜瓜幼苗的生长和相关光合指标。适宜浓度外源SA能不同程度缓解甜瓜幼苗所受Cd2+胁迫伤害,并以100μmol·L-1 SA处理效果最好,其显著促进了幼苗生长,提高了叶片叶绿素含量、净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs),以及PSⅡ最大光化学效率(Fv/Fm)、PSⅡ天线转化效率(Fv′/Fm′)、实际光化学效率(ФPSⅡ)、光化学荧光猝灭系数(qP)和光化学反应能量(P);显著降低了初始荧光(F0)、非光化学荧光猝灭系数(NPQ)、天线热耗散能量(D)和非光化学反应耗散能量(E)。研究表明,外源SA缓解甜瓜幼苗Cd2+胁迫伤害具有剂量效应,以100μmol·L-1 SA的效果最好,有利于甜瓜幼苗在Cd2+胁迫下光合作用的维持,提高光合电子传递效率和对光能的捕获与转换,降低Cd2+胁迫对植物的损伤,从而促进生长。     

Biologically Inspired Scene Context for Object Detection Using a Single Instance

This paper presents a novel object detection method using a single instance from the object category. Our method uses biologically inspired global scene context criteria to check whether every individual location of the image can be naturally replaced by the query instance, which indicates whether there is a similar object at this location. Different from the traditional detection methods that only look at individual locations for the desired objects, our method evaluates the consistency of the entire scene. It is therefore robust to large intra-class variations, occlusions, a minor variety of poses, low-revolution conditions, background clutter etc., and there is no off-line training. The experimental results on four datasets and two video sequences clearly show the superior robustness of the proposed method, suggesting that global scene context is important for visual detection/localization.