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In this study, we investigated the potential of the photochemical resistance index (PRI) to track photosynthetic activity under water stress conditions by measuring PRI, leaf fluorescence, the xanthophyll cycle and photosynthetic activity in different forest tree species subjected to progressive drought. The PRI declined with pre-dawn water potential and a significant relationship between PRI and the xanthophyll de-epoxidation state (DEPS) was observed, although with large interspecific variability in the sensitivity of PRI to changes in DEPS. For single tree species, a strong relationship was observed on either PRI light saturated photosynthesis or PRI maximum photochemical efficiency of PSII (DF/Fm 0); a larger variability in both relationships was apparent when data from different species were pooled together. However, an improved correlation was shown only in the former relationship by plotting the DPRI (dawn PRI minus the midday PRI values). Thus, we conclude that PRI is able to provide a good estimate of maximum CO2 assimilation at saturating light and DF/Fm 0 for single tree species, despite the severe drought conditions applied. PRI should be applied more cautiously when dealing with multispecific forests because of confounding factors such as the strong interspecific differences in the initial value of PRI and in the sensitivity of PRI to changes in DEPS in response to drought.

The Photochemical Reflectance Index (PRI) has been proposed as a tool for the estimation of leaf and canopy light-use efficiency and photosynthesis from remote-sensing data. The application of the index is based on more than fifteen years of spectroscopic studies at the leaf level, which support it with a sound physiological basis. In the present study, the correlation between PRI and instantaneous light-use efficiency was estimated across a range of vegetation types in the San Rossore Regional Park, a CHRIS-Proba core site. The relationship was also tested over an entire season for a pine forest in the Park where carbon fluxes have been monitored by eddy-covariance over the last five years. Seasonal changes in photosynthetic potential were also monitored at the site, in order to test the correlation with PRI reported in the literature. In September 2004, estimates of canopy PRI from CHRIS images were compared with leaf-level measurements from 13 plots corresponding to different vegetation types. The results were used to extrapolate leaf-level information to the entire scene.

Methods for chlorosis detection and physiological condition monitoring in Vitis vinifera L, through accurate chlorophyll a and b content (Cab) estimation at lead and canopy levels are presented in this manuscript. A total of 24 vineyards were identified for field and airborne data collection with the Compact Airborne Spectrographic Imager (CASI), the Reflective Optics System Imaging Spectrometer (ROSIS) and the Digital Airborne Imaging Spectrometer (DAIS-7915) hyperspectral sensors in 2002 and 2003 in northem Spain, comprising 103 study areas of 10 * 10 m in size, with a total of 1467 leaves collected for determination of pigment concentration. A subsample of 605 leaves was used for measuring the optical properties of reflectance and tranmittance with a Li-Cor 1800-12 Integrating Sphere coupled by a 200um diameter single mode fiber to an Ocean Optics model USB2000 spectrometer. Several narrow-band vegetation indices were calculated from lead reflectance spectra, and the PROSPECT leaf optical model was used for inversion using the extensive database od lead optical properties. Results showed that the best indicators for chlorophyll content estimation in V. vinifera L. leaves were narrow-band hyperspectral indices calculated in the 700-750 nm spectral region (r2 ranging between 0.8 and 0.9), with poor performance of traditional indices such as the Normalized Difference Vegetation Index (NDVI). Results for other biochemicals indicated that the Structure Insensitive Pigment Index (SIPI) and the Photochemical Reflectance Index (PRI) were more sensitice to carotenoids C x+c and chlorophyll-carotenoid ratios Cab/Cx+c than to chlorophyll content Cab. Chlorophyll a and b estimation by inversion of the PROSPECT leaf model on V. vinifera L. spectra was successful, yielding a determination coefficient of r2=0.95, with an RMSE=5.3ug/cm2. The validity of leaf-level indices for chlorophyll content estimation at the canopy level in V. vinifera L. was studied using the scaling-up approach that links PROSPECT and rowMCRM canpy reflectance simulation to account for the effects of vineyard structure, vine dimensions, row orientation and soil and shadow effects on the canopy reflectance. The index calculated as a combination of the Transformed Chlorophyll Absorption in Reflectance Index (TCARI), and the Optimized Soil-Adjusted Vegetation Index (OSAVI) in the form RCARI/OSAVI was the most consistent index for estimating Cab on aggregated and pure vine pixels extracted from 1 m CASI and ROSIS hyperspectral imagery. Predictive relationships were developed with PROSPECT-rowMCRM model between Cab and TCARI/OSAVI as function of LAI, using field-measured vine dimensions and image-extracted siul background, row-orientation and viewing geometry values. Prediction relationships for Cab content with TCARI/OSAVI were successfuly applied to the 103 study sites imaged on 24 fields by ROSIS and CASI airborne sensors, yielding r2=0.67 and RMSE-11.5ug/cm2.

Hydrogen peroxide is a precursor to damage mechanisms in numerous applications; its monitoring is important and challenging. The effect of temperature on the perforomance and durability of a recently developed optical fiber sensors sensitice to the presence of hydrogen peroxide in low concentrations is investigated. The sensors are fabricated by immobilizing Prussian blue within a multilayer of electrostatically self-assembled polyelectrolytes. The sensing principle of this optical electrode relies on the change in the intensity of the reflected light when Prussian white is oxidized back to the blue state due to the presence of hydrogen peroxide. The amplitude of the intensity of the reflected light is found to vary with temperature in a quadratic fashion, but the characteristic response time which correlates with vary with temperature in a quadratic fashion, but the characteristic response time which correlates with concentration remains constant. Thus the sensing device retains its abilities to determine and quantify the concentration of hydrogen peroxide in a liquid solution. Additionally, the degradation of these fiber sensors when subjected to high temperature is examined. Four optical fiber sensing devices were subjected to different testing conditions and a characterization protocol that included: measurement of the intensity of the intensity of the cyanide strtch(2150 cm-1) via Raman micro spectroscopy; imaging with scanning electron microscopy; and measurement of the presence of iron ions using energy dispersive X-ray spectroscopy.

The fraction of absorbed photosynthetically active radiation, fAPAR, is an important biophysical characteristic in models of gas exchange between the terrestrial boundary layer and the atmosphere, as well as in the analysis of vegetation productivity. Synoptic estimation of fAPAR has been performed by using NDVI as a linear proxy of fAPAR, despite the saturation of NDVI at fAPAR beyond 0.7. This paper analyzes the NDVI/fAPAR relationship in row crops (i.e. maize and soybean), and evaluates alternative vegetation indices to overcome the loss of sensitivity of NDVI at moderate-to-high vegetation biomass. Red-edge NDVI, which uses NIR and a band around 700 nm and the recently proposed Wide Dynamic Range Vegetation Index, which uses red and NIR bands only, were found to be sensitive to fAPAR variation along its entire range and exhibited significant increase in sensitivity to fAPAR.

Green leaf area index (LAI) is an important variable for climate modeling, estimates of primary production, agricultural yield forecasting, and many other diverse applications. Remotely sensed data provide considerable potential for estimating LAI at local, regional, and global scales. The goal of this study was to retrieve green LAI from MODIS 250-m vegetation index (VI) data for irrigated and rainfed maize and soybeans. The performance of both MODIS-derived NDVI and Wide Dynamic Range Vegetation Index (WDRVI) were evaluated across three growing seasons (2002 through 2004) over a wide range of LAI and also compared to the performance of NDVI and WDRVI derived from reflectance data collected at closerange across the same field locations. The NDVI vs. LAI relationship showed asymptotic behavior with a sharp decrease in the sensitivity of the NDVI to LAI exceeding 2 m2/m2 for both crops. WDRVI vs. LAI relation was linear across the entire range of LAI variation with determination coefficients above 0.93. Importantly, the coefficients of the close-range WDRVI vs. LAI equation and the MODISretrieved WDRVI vs. LAI equation were very close. The WDRVI was found to be capable of accurately estimating LAI across a much greater LAI range than the NDVI and can be used for assessing even slight variations in LAI, which are indicative of the early stages of plant stress. These results demonstrate the new possibilities for analyzing the spatio-temporal variation of the LAI of crops using multi-temporal MODIS 250-m imagery.

The chemical kinetics of the silver-mediated growth of gold nanorods prepared by the reduction of gold precursor in aqueous cetyltrimethylammonium bromide (CTAB) solution has been systematically studied using spectroscopic monitoring and electron microscopy. The rate of monomer depletion d[Aun+]/dt has a linear dependence on both [Aun+] and seed nuclei concentration at 30 C. Particle growth is significantly retarded by hexadecyltrimethylammonium bromide (CTAB) and KBr, with the order ca. 1 for [Br ]. The rate of nanoparticle growth is dependent on the reducing ascorbate monoanion concentration and is consequently highly pH dependent around the pKa 1 of ascorbic acid, while AgNO3 retards the observed kinetics for both the growth of nanorods from ca. 2 nm seed nuclei and the overgrowth of Au nanorods.

介绍了利用双光路差分吸收光谱(DOAS)技术检测大气气溶胶并反演其粒谱分布的新方法,该方法解决了DOAS技术中光源绝对光强难以测量的难题,去除了由于光源自身波动造成的影响,在250-650nm范围内成功的反演处气溶胶的消光系数以及0.1-1.75um谱段的粒谱分布,通过与光学粒子计数器的对比实验证实该方法的可行性。

The colour of blue-green bird eggs has been hypothesized to signal female quality to attending males, who may adjust their level of investment in the brood accordingly. The hypothesis has gained support in studies of Spanish pied flycatchers Ficedula hypoleuca. We performed a cross-fostering experiment in a Norwegian population of pied flycatchers to provide an independent test of the sexually selected egg colour hypothesis in this species. Egg colour was not significantly correlated with estimates of female quality (clutch size, average egg volume, first egg laying date and feeding rate). There was a significant decrease in chroma and increase in brightness and egg volume during the laying sequence, with some marked differences between six-egg and seven-egg clutches that might reflect differences in female quality. However, we found no significant influence of egg colour (foster or original clutch) on male feeding rate or offspring viability (hatching success, average mass and fledging success) and no significant difference in feeding rate for males with six-egg and seven-egg foster or original clutches. We conclude that Norwegian male pied flycatchers do not use egg colour as a cue to female quality, thus questioning the generality of previous support for the sexually selected egg colour hypothesis from this species.

Leaf pigment content and composition provide important information about plant physiological status. Reflectance measurements offer a rapid, nondestructive technique to estimate pigment content. This paper describes a recently developed three-band conceptual model capable of remotely estimating total of chlorophylls, carotenoids and anthocyanins contents in leaves from many tree and crop species. We tuned the spectral regions used in the model in accord with pigment of interest and the optical characteristics of the leaves studied, and showed that the developed technique allowed accurate estimation of total chlorophylls, carotenoids and anthocyanins, explaining more than 91%, 70% and 93% of pigment variation, respectively. This new technique shows a great potential for noninvasive tracking of the physiological status of vegetation and the impact of environmental changes.

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