Time-resolving luminescence techniques for possible detection of forest decline

Needles from spruces at different environmental and physiological conditions were analyzed by picosecond fluorescence spectroscopy using a novel laser diode and single photon counting detection. The decay curves of chlorophyll fluorescence showed a superposition of three exponentially decaying components with time constants of T1 = 100-200 ps, T2 = 300-500 ps and T3 = 2.0-3.5 ns. A high relative intensity of the long-lived component was found in damaged spruces as well as in trees showing first symptoms of yellowing, needle loss or parasite infection, although all measurements were carried out with green needles which appeared visually intact. Therefore, fluorescence spectroscopy with subnanosecond time resolution seems to be a valuable attempt for an early detection of forest decline.     

Microbat responses to forest decline

Tree declines have been recorded across forests and woodlands on most continents, causing tree mortality over thousands of square kilometres, yet the impact of tree declines upon mammals have only rarely been quantified. Once the dominant tree over the western parts of the Swan Coastal Plain in Western Australia, tuart (Eucalyptus gomphocephala) forest has been reduced to less than a third of its former range through clearing for agriculture and urban development. Additionally, over the last 30 years, the remnant population has been heavily impacted by a decline that has an unknown cause, but is likely related to a root pathogen coupled with abiotic factors (reduced rainfall, increased salinity and elevated temperatures). Tuart decline is evident as marked canopy dieback, replacement with epicormic growth and increasing bare branches, while leaf litter is lost from the tree surrounds. We examined the effect of tuart decline and other vegetation measures upon bat activity using auditory monitoring. Vegetation structure was correlated with Vespertilionidae bat activity. Falsistrellus mackenziei were more likely to forage around healthy canopies (activity positively correlated with tuart crown density and negatively correlated with tuart crown dieback). By contrast, the other three taxa were more often encountered in declining rather than healthy tuart sites. Chalinolobus gouldii was positively associated with tuart crown dieback. Activity of Vespadelus regulus and Nyctophilus spp. (species not distinguishable from their calls) were significantly positively correlated with an open tall canopy (positively with cover of plants >10 m tall and negatively with overall canopy cover density). There were no vegetation measurements that were strong predictors of activity of two Molossidae species (Ozimops kitcheneri and Austronomus australis), which intercept insects above the forest canopy. This study clearly reveals different factors influencing the activity of bat taxa, which are likely related to where they feed and their manoeuvrability around tree canopies.     

Liquid chromatography/luminescence techniques

The techniques of pre- and post-column reactions in HPLC with fluorimetric detection for catecholamines (CAs) were described. The post-column reactor based on trishydroxyindole formation have frequently used in the routine analysis of CAs. The fluorescence intensity of the derivative dopamine (DA) at 520 nm (with exitation at 410 nm) is weaker than that of the norepinephrine (NE) and epinephrine (E) derivatives. Although urinary DA can be detected by using this method, its detection in plasma is difficult. Recently a new pre-column derivatization method using 1,2-diphenylethylenediamine (DPE) was found in Ohkura's laboratory. After the clean-up using a cation-exchange column, CAs were converted into the fluorescent compounds by reaction with DPE. The limites of detection for NE, E and DA were about 2 fmol at a signal-to-noise ratio of 2. DA in plasma can be determined by this method. A modified THI technique with electrochemical oxidation was examined. The above methods are very sensitive and selective for the measurement of CAs (NE, E and/or DA) in biological samples.     

防护林衰退研究进展

森林衰退问题已成为21世纪全球环境发展的难题之一,而占中国森林总面积31%的防护林出现部分严重衰退,形势严峻.本文在广泛收集国内外相关文献的基础上,提出防护林在生长发育过程中出现的生理机能下降,因生产力、地力衰退、林分结构不合理等导致防护效能下降的状态即为防护林衰退.总结了引起防护林衰退的主要原因,包括:没有适地适树、林分结构不合理、缺乏合理的经营管理、人为干扰和频发的自然干扰等.本文从防护林衰退机理、防护林结构、经营管理、人为干扰、林种结构等方面分析了中国防护林研究存在的主要问题,建议今后应加强对防护林衰退形成过程和机制、衰退的早期诊断与评价、防护林衰退防治以及防护林宏观布局和应对干扰策略等方面的研究.     

The contribution of ozone to forest decline

More than 10 years of intensive research into forest decline in Germany has ascertained that the full extent of the visible damage cannot be explained by just one of the current hypotheses on forest decline. One of the prominent hypotheses is that chronic exposure of forest trees to ozone is probably one of the primary causes of forest decline. The aim of this paper is the critical review of a number of recent results dealing with the ozone hypothesis from a plant physiological point of view. The synopsis focusses on the effects of ozone on conifers because the most extensive data are available for coniferous trees, especially for spruce ( Picea sp.) and pine ( Pinus sp.) trees.     

Enzyme-amplified lanthanide luminescence for enzyme detection in bioanalytical assays

Enzyme-amplified lanthanide luminescence (EALL) is a new method which has been developed for enzymatically amplified signal detection in ultrasensitive bioanalytical assays where an enzyme is used as label or is itself the analyte of interest. Signal generation is performed by enzymatically transforming a substrate into a product which forms a luminescent lanthanide chelate; the product chelate can then be detected using time-resolved or normal fluorescence methods. Alkaline phosphatase substrates have been developed and demonstrated in a model immunoassay in microwell format. The method has also been demonstrated for detection of a variety of other hydrolytic and oxidative enzymes. Thus the EALL method shows promise for use in a wide variety of bioanalytical applications.     

Ecological succession following forest decline in a xeric oak forest of south-central United States

Aims The loss of canopy trees associated with forest decline can greatly influence the species composition and structure of a forest and have major impacts on the ecosystem. We studied the changes in forest composition and structure 1 and 5 years following nearly total canopy mortality on several hundreds of hectares of xeric oak forests in south-central United States. Because the forests were within an ecotonal vegetation type composed of a mosaic of forest, savanna and grassland, we sought to learn whether forest decline areas would recover to forest or change to more open savanna and grassland conditions in the landscape pattern of vegetation. Because low intensity fire shaped the vegetation type, we sought to learn whether fire would keep the decline areas open.Methods The study was conducted in a xeric oak forest in east-central Oklahoma, USA. Randomly located vegetation and regeneration surveys were conducted in decline and non-decline stands 1 and 5 years following nearly total canopy mortality. Diameter at breast height (DBH), regeneration and sprout origin were recorded for all woody species.Important findings The major canopy species post oak (Quercus stellata Wangenh.), blackjack oak (Quercus marilandica Muenchh.) and black hickory (Carya texana Buckl.) suffered 85–92% mortality; however, minor canopy components experienced limited mortality. Mortality affected all size classes of canopy trees except those below 5cm breast height diameter. There was abundant regeneration of all species and fire seemed to maintain a high level of sprouting. Decline appeared to decrease the relative importance of stump sprouting and increase other types including root sprouts. Decline areas had abundant true seedlings, with stem origin from a root with the same diameter as the stem, which is very unusual for xeric oak forests. Regeneration height in decline areas was twice that of non-decline forests. Our findings suggest that forest decline may lead to: (i) reduced oak dominance and species change in the canopy, (ii) change in reproduction type to increase success of true seedlings and maintain genetic diversity of oaks.     

Modeling and simulation of luminescence detection platforms

Motivated by the design of an integrated CMOS-based detection platform, a simulation model for CCD and CMOS imager-based luminescence detection systems is developed. The model comprises four parts. The first portion models the process of photon flux generation from luminescence probes using ATP-based and luciferase label-based assay kinetics. An optics simulator is then used to compute the incident photon flux on the imaging plane for a given photon flux and system geometry. Subsequently, the output image is computed using a detailed imaging sensor model that accounts for photodetector spectral response, dark current, conversion gain, and various noise sources. Finally, signal processing algorithms are applied to the image to enhance detection reliability and hence increase the overall system throughput. To validate the model, simulation results are compared to experimental results obtained from a CCD-based system that was built to emulate the integrated CMOS-based platform.     

Drought-induced forest decline: causes, scope and implications

A large number of episodes of forest mortality associated with drought and heat stress have been detected worldwide in recent decades, suggesting that some of the world's forested ecosystems may be already responding to climate change. Here, we summarize a special session titled 'Drought-induced forest decline: causes, scope and implications' within the 12th European Ecological Federation Congress, held in ávila (Spain) from 25 to 29 September 2011. The session focused on the interacting causes and impacts of die-off episodes at the community and ecosystem levels, and highlighted recent events of drought- and heat-related tree decline, advances in understanding mechanisms and in predicting mortality events, and diverse consequences of forest decline. Talks and subsequent discussion noted a potentially important role of carbon that may be interrelated with plant hydraulics in the multi-faceted process leading to drought-induced mortality; a substantial and yet understudied capacity of many forests to cope with extreme climatic events; and the difficulty of separating climate effects from other anthropogenic changes currently shaping forest dynamics in many regions of the Earth. The need for standard protocols and multi-level monitoring programmes to track the spatio-temporal scope of forest decline globally was emphasized as critical for addressing this emerging environmental issue.     

Primary and secondary causes and consequences of contemporary forest decline

Realization that forest decline (Waldsterben) has become an ecological crisis throughout the developed world has resulted in massive research efforts to determine the causes of declines. It is now recognized that no single causal factor is responsible, but that there are a variety of anthropogenic causal factor complexes interacting with natural events and processes that, together, induce stresses in forests that culminate in declines of individual plants and of ecosystems. It is the thesis of this article that forest declines involve all biotic and abiotic facets and parameters of forested ecosystems and that the declines are themselves new causal factor complexes that continue to affect the stability of forested ecosystems independently of the initial causal factor complexes. Lacking direct field or laboratory studies on these cascades of causes and effects, this article attempts to utilize the growing body of information on plant physiological ecology to provide a heuristic framework for evaluating long-term forest declines.     

Dual analyte detection using tandem flash luminescence

A heterogeneous, dual analyte-binding assay which makes use of the flash luminescence from both aequorin and an acridinium-9-carboxamide label is presented. The signal generating species were triggered both differentially and sequentially using Ca(2+) followed by basic peroxide. Both signals were resolved readily using a single photomultiplier tube without the need for multiwavelength detection. To demonstrate the tandem luminescence concept in a model assay system, dose-response curves for two analytes, biotinylated BSA and myoglobin, were generated using a competitive binding format. Because of the relatively short assay time and the well-resolved signals, this format will be useful in the development of dual analyte high-throughput assays.     

Spatial dynamics of forest decline: the role of neighbouring trees

Abstract. Changes in horizontal structure and the influence of neighbours on tree vitality were studied in a spruce forest under air pollution stress. Five permanent plots along an altitudinal gradient in the Krkono?e Mts., Czech Republic, were monitored for 18 years. Digitized maps of each plot were used for the analysis: the health of each tree, expressed by the defoliation degree was recorded each year, the biometrical characteristics were measured at five-year intervals. Various indices of neighbourhood competition were used to evaluate the interference with neighbours. The results show that the suppressed trees are most susceptible to other environmental stresses, particularly to the air pollution stress. Similarly, tree damage is more severe in plots near the natural timberline, where the trees are close to their natural environmental limits. The spatial pattern of surviving trees changes towards regularity at a scale of 2–5 m (K-function analysis) when the suppressed trees, usually those with close neighbours, die.     

Upconversion luminescence resonance energy transfer-based aptasensor for the sensitive detection of oxytetracycline

In this work, a biosensor based on luminescence resonance energy transfer (LRET) from NaYF₄:Yb,Tm upconversion nanoparticles (UCNPs) to SYBR Green I has been developed. The aptamers are covalently linked to UCNPs and hybridized with their complementary strands. The subsequent addition of SYBR Green allows SYBR Green I to insert into the formed double-stranded DNA (dsDNA) duplex and brings the energy donor and acceptor into close proximity, leading to the fluorescence of UCNPs transferred to SYBR Green I. When excited at 980 nm, the UCNPs emit luminescence at 477 nm, and this energy is transferred to SYBR Green I, which emits luminescence at 530 nm. In the presence of oxytetracycline (OTC), the aptamers prefer to bind to its corresponding analyte and dehybridize with the complementary DNA. This dehybridization leads to the liberation of SYBR Green I, which distances SYBR Green I from the UCNPs and recovers the UCNPs' luminescence. Under optimal conditions, a linear calibration is obtained between the ratio of I₅₃₀ to I₄₇₇ nm (I₅₃₀/I₄₇₇) and the OTC concentration, which ranges from 0.1 to 10 ng/ml with a limit of detection (LOD) of 0.054 ng/ml.     

Saliva-based point-of-care testing techniques for COVID-19 detection

Highlights
1. The advantages of COVID-19 detection in saliva were systematically introduced.
2. Saliva-based POCT technologies for the detection of COVID-19 were reviewed.
3. A positive correlation between COVID-19 antibodies in saliva and serum was demonstrated.     

神经递质的可视化荧光检测技术研究进展

神经递质是神经系统中至关重要的组成部分,神经递质释放的时间和空间变化是神经网络中信息处理的核心,可视化监测神经递质的生物传感器是探究各类生理和病理活动的重要工具。文中综述了近年来具有较高时间和空间分辨率的监测神经递质时空分布变化技术的研究进展,介绍了对谷氨酸、多巴胺、γ-氨基丁酸和乙酰胆碱这4类重要的神经递质的检测方法,并归纳总结了各类检测方法的基本原理和优缺点,为设计具有高时空分辨率的神经递质传感器提供一个较为系统的参考。     

Chemiluminescence detection with separation techniques for bioanalytical applications

Chemiluminescence detection is known to be a sensitive, selective, and versatile method that can be used in combination with separation techniques such as high-performance liquid chromatography, capillary electrophoresis, and chip electrophoresis. This article reviews the bioanalytical applications of a combination of chemiluminescence detection and separation techniques published in the literature between 1999 and 2008. Luminol chemiluminescene, peroxyoxalate chemiluminescence, and electrochemiluminescence have been mainly used for bioanalytical application. In this paper, only the applications of the method for the analysis of biosamples, serum, plasma, urine, and tissue samples are discussed.