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The use of non-destructive commercial near-infrared (NIR) spectroscopy to estimate Brix% was verified using all samples of cherry tomato 'TY Chika', currant tomato 'Microbeads', and the M&S or market-purchased and supplemental local source tomatoes. Additionally, the relationship between fresh weight and Brix% of all samples was examined. These tomatoes had a diversity of cultivars, growing methods, harvest timing, and production locations and varied widely from 4.0% to 14.2% for Brix% and 1.25 g to 95.84 g for fresh weight. Regardless of the diversity of all samples, it was revealed that the refractometer-based Brix% (y) was practically estimated from the NIR-derived Brix% value (x) using a relationship of y = x (RMSE = 0.747 Brix%) after only a one-time calibration for the NIR spectrometer offset. An inverse relationship between fresh weight and Brix% could be modeled using a hyperbolic curve fit, and the model showed an R2 of 0.809 except for 'Microbeads'. The Brix% of 'TY Chika' was highest on average (9.5%) and had a large difference from 6.2 to 14.2% among the samples. Data distribution of cherry tomato groups such as 'TY Chika' and M&S cherry tomatoes was closer, indicating a roughly linear correlation between fresh weight and Brix%.

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BACKGROUND: Measurement of plant structure is useful in monitoring plant conditions and understanding the responses of plants to environmental changes. 3D imaging technologies, especially the passive-SfM (Structure from Motion) algorithm combined with a multi-camera photography (MCP) system has been studied to measure plant structure due to its low-cost, close-range, and rapid image capturing ability. However, reconstruction of 3D plant models with complex structure is a time-consuming process and some systems have failed to reconstruct 3D models properly. Therefore, an MCP based SfM system was developed and an appropriate reconstruction method and optimal range of camera-shooting angles were investigated. RESULTS: An MCP system which utilized 10 cameras and a rotary table for plant was developed. The 3D mesh model of a single leaf reconstruction using a set of images taken at each viewing zenith angle (VZA) from 12° (C2 camera) to 60° (C6 camera) by the MCP based SfM system had less undetected or unstable regions in comparison with other VZAs. The 3D mesh model of a whole plant, which merged 3D dense point cloud models built from a set of images taken at each appropriate VZA (Method 1), had high accuracy. The Method 1 error percentages for leaf area, leaf length, leaf width, stem height, and stem width are in the range of 2.6-4.4%, 0.2-2.2%, 1.0-4.9%, 1.9-2.8%, and 2.6-5.7% respectively. Also, the error of the leaf inclination angle was less than 5°. Conversely, the 3D mesh model of a whole plant built directly from a set of images taken at all appropriate VZAs (Method 2) had lower accuracy than that of Method 1. For Method 2, the error percentages of leaf area, leaf length, and leaf width are in the range of 3.1-13.3%, 0.4-3.3%, and 1.6-8.6%, respectively. It was difficult to obtain the error percentages of stem height and stem width because some information was missing in this model. In addition, the calculation time for Method 2 was 1.97 times longer computational time in comparison to Method 1. CONCLUSIONS: In this study, we determined the optimal shooting angles on the MCP based SfM system developed. We found that it is better in terms of computational time and accuracy to merge partial 3D models from images taken at each appropriate VZA, then construct complete 3D model (Method 1), rather than to construct 3D model by using images taken at all appropriate VZAs (Method 2). This is because utilization of incorporation of incomplete images to match feature points could result in reduced accuracy in 3D models and the increase in computational time for 3D model reconstruction.

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Chlorophyll is one of the primary pigments of plant leaves, and changes in its content can be used to characterize the physiological status of plants. Spectral indices have been devised and validated for estimating leaf chlorophyll content (LCC). However, most of the existing spectral indices do not consider the influence of angular reflection on the accuracy of the LCC estimation. In this study, the spectral reflectance factors of leaves from three plant species were measured from several observations in the principal plane. The relationship between the existing spectral indices and the LCC from different directions suggests that the directional reflection of a leaf surface impacts the accuracy of its LCC estimation. Subsequently, the ratio of reflectance differences, that is, the modified Datt index, was tested to reduce the directional reflection effect when predicting LCC. Our results indicated that the modified Datt index not only estimated LCC with high accuracy for all observation directions and plant species but also consistently predicted the LCC of each species in individual observation directions. Our method opens the possibility for optical detection of LCC using multiangular spectral reflection, which is convenient for plant science studies focused on the variation in LCC.

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BACKGROUND: Leaf chlorophyll content (LCC) provides valuable information about plant physiology. Most of the published chlorophyll vegetation indices at the leaf level have been based on the spectral characteristics of the adaxial leaf surface, thus, they are not appropriate for estimating LCC when both the adaxial and abaxial leaf surfaces influence the spectral reflectance. We attempted to address this challenge by measuring the spectral reflectance of the adaxial and abaxial leaf surfaces of several plant species at different growth stages using a portable field spectroradiometer. The relationships between more than 30 published reflectance indices with LCC were analyzed to determine which index estimated LCC most effectively. Additionally, since the relationships determined on one set of samples might have poor predictive performances when applied to other samples, a robust wavelength region is required to render the spectral index generally applicable, regardless of the leaf surface or plant species. RESULTS: The Modified Datt (MDATT) index, which is the ratio of reflectance difference defined as (Rλ3 - Rλ1)/(Rλ3 - Rλ2), exhibited the strongest correlation (R2 = 0.856, RMSE = 6.872 µg/cm2), with LCC of all the indices tested when all the leaf samples from the adaxial and abaxial surfaces were combined. The optimal wavelength regions, which were derived from the contour maps of R2 between the MDATT index and LCC for the datasets of one side or both leaf surfaces of each plant species and their intersection, indicated that the red-edge to near-infrared wavelength (723-885 nm) was optimal for λ1, while the red-edge region (697-771 nm) was optimal for λ2 and λ3. In these optimal wavelength regions, when the MDATT index was used to estimate LCC, an R2 higher than 0.8 could be obtained. The correlation of the MDATT index with LCC was the same when the positions of λ2 and λ3 were exchanged in the index. CONCLUSIONS: MDATT is proposed as an optimal index for the remote estimation of vegetation chlorophyll content across several plant species in different growth stages when reflectance from both leaf surfaces is considered. The red-edge to near-infrared wavelength (723-885 nm) for λ1, as well as the red-edge region (697-771 nm) for λ2 or λ3, are considered to be the most robust for constructing the MDATT index for estimating LCC, regardless of the leaf surface or plant species.

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For plant breeding and growth monitoring, accurate measurements of plant structure parameters are very crucial. We have, therefore, developed a high efficiency Multi-Camera Photography (MCP) system combining Multi-View Stereovision (MVS) with the Structure from Motion (SfM) algorithm. In this paper, we measured six variables of nursery paprika plants and investigated the accuracy of 3D models reconstructed from photos taken by four lens types at four different positions. The results demonstrated that error between the estimated and measured values was small, and the root-mean-square errors (RMSE) for leaf width/length and stem height/diameter were 1.65 mm (R² = 0.98) and 0.57 mm (R² = 0.99), respectively. The accuracies of the 3D model reconstruction of leaf and stem by a 28-mm lens at the first and third camera positions were the highest, and the number of reconstructed fine-scale 3D model shape surfaces of leaf and stem is the most. The results confirmed the practicability of our new method for the reconstruction of fine-scale plant model and accurate estimation of the plant parameters. They also displayed that our system is a good system for capturing high-resolution 3D images of nursery plants with high efficiency.

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Quick non-destructive assessment of leaf chlorophyll content (LCC) is important for studying phenotypes related to plant growth and stress resistance. This study was undertaken to investigate the quantitative relationship between LCC and different vegetation indices (VIs) on both adaxial and abaxial surfaces of white poplar (Populus alba), which has dense tubular hairs on its abaxial surface, and Chinese elm (Ulmus pumila var. pendula), which does not show obvious superficial differences except for lighter colour on the abaxial surface. Some published and newly developed VIs were tested to relate them to LCC. The results showed that most of the published VIs had strong relationships with LCC on the one-surface dataset, but did not show a clear relationship with LCC when both adaxial and abaxial surface reflectance data were included. Among the reflectance indices tested, the modified Datt index, (R719-R726)/(R719-R743), performed best and is proposed as a new index for remote estimation of chlorophyll content in plants with varying leaf surface structures. It explained 92% of LCC variation in this research, and the root mean square error of the LCC prediction was 5.23 µg/cm(2). This new index is insensitive to the effects of adaxial and abaxial leaf surface structures and is strongly related to the variation in reflectance caused by chlorophyll content.

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This paper illustrates the possibility of measuring chlorophyll (Chl) content and Chl fluorescence parameters by the solar-induced Chl fluorescence (SIF) method using the Fraunhofer line depth (FLD) principle, and compares the results with the standard measurement methods. A high-spectral resolution HR2000+ and an ordinary USB4000 spectrometer were used to measure leaf reflectance under solar and artificial light, respectively, to estimate Chl fluorescence. Using leaves of Capsicum annuum cv. 'Sven' (paprika), the relationships between the Chl content and the steady-state Chl fluorescence near oxygen absorption bands of O2B (686nm) and O2A (760nm), measured under artificial and solar light at different growing stages of leaves, were evaluated. The Chl fluorescence yields of ΦF 686nm/ΦF 760nm ratios obtained from both methods correlated well with the Chl content (steady-state solar light: R(2) = 0.73; artificial light: R(2) = 0.94). The SIF method was less accurate for Chl content estimation when Chl content was high. The steady-state solar-induced Chl fluorescence yield ratio correlated very well with the artificial-light-induced one (R(2) = 0.84). A new methodology is then presented to estimate photochemical yield of photosystem II (ΦPSII) from the SIF measurements, which was verified against the standard Chl fluorescence measurement method (pulse-amplitude modulated method). The high coefficient of determination (R(2) = 0.74) between the ΦPSII of the two methods shows that photosynthesis process parameters can be successfully estimated using the presented methodology.

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BACKGROUND: The color of crop leaves is closely correlated with nitrogen (N) status and can be quantified easily with a digital still color camera and image processing software. The establishment of the relationship between image color indices and N status under natural light is important for crop monitoring and N diagnosis in the field. In our study, a digital still color camera was used to take pictures of the canopies of 6 rice (Oryza sativa L.) cultivars with N treatments ranging from 0 to 315 kg N ha(-1) in the field under sunny and overcast conditions in 2010 and 2011, respectively. RESULTS: Significant correlations were observed between SPAD readings, leaf N concentration (LNC) and 13 image color indices calculated from digital camera images using three color models: RGB, widely used additive color model; HSV, a cylindrical-coordinate similar to the human perception of colors; and the L (*) a (*) b (*) system of the International Commission on Illumination. Among these color indices, the index b (*) , which represents the visual perception of yellow-blue chroma, has the closest linear relationship with SPAD reading and LNC. However, the relationships between LNC and color indices were affected by the developmental phase. Linear regression models were used to predict LNC and SPAD from color indices and phasic development. After that, the models were validated with independent data. Generally, acceptable performance and prediction were found between the color index b (*) , SPAD reading and LNC with different cultivars and sampling dates under different natural light conditions. CONCLUSIONS: Our study showed that digital color image analysis could be a simple method of assessing rice N status under natural light conditions for different cultivars and different developmental stages.

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Steady-state and dynamic gas exchange responses to ozone visible injury were investigated in an ozone-sensitive poplar clone under field conditions. The results were translated into whole tree water loss and carbon assimilation by comparing trees exposed to ambient ozone and trees treated with the ozone-protectant ethylenediurea (EDU). Steady-state stomatal conductance and photosynthesis linearly decreased with increasing ozone visible injury. Dynamic responses simulated by severing of a leaf revealed that stomatal sluggishness increased until a threshold of 5% injury and was then fairly constant. Sluggishness resulted from longer time to respond to the closing signal and slower rate of closing. Changes in photosynthesis were driven by the dynamics of stomata. Whole-tree carbon assimilation and water loss were lower in trees exposed to ambient O(3) than in trees protected by EDU, both under steady-state and dynamic conditions. Although stomatal sluggishness is expected to increase water loss, lower stomatal conductance and premature leaf shedding of injured leaves aggravated O(3) effects on whole tree carbon gain, while compensating for water loss. On average, WUE of trees exposed to ambient ozone was 2-4% lower than that of EDU-protected control trees in September and 6-8% lower in October.

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This study aimed to evaluate the photochemical reflectance index (PRI) for assessing plant photosynthetic performance throughout the plant life cycle. The relationships between PRI, chlorophyll fluorescence parameters, and leaf pigment indices in Solanum melongena L. (aubergine; eggplant) were studied using photosynthetic induction curves both in short-term (diurnal) and long-term (seasonal) periods under different light intensities. We found good correlations between PRI/non-photochemical quenching (NPQ) and PRI/electron transport rate (ETR) in the short term at the same site of a single leaf but these relationships did not hold throughout the life of the plant. In general, changes in PRI owing to NPQ or ETR variations in the short term were <20 % of those that occurred with leaf aging. Results also showed that PRI was highly correlated to plant pigments, especially chlorophyll indices measured by spectral reflectance. Moreover, relationships of steady-state PRI/ETR and steady-state PRI/photochemical yield of photosystem II (Φ(PSII)) measured at uniform light intensity at different life stages proved that overall photosynthesis capacity and steady-state PRI were better correlated through chlorophyll content than NPQ and xanthophylls. The calibrated PRI index accommodated these pigments effects and gave better correlation with NPQ and ETR than PRI. Further studies of PRI indices based on pigments other than xanthophylls, and studies on PRI mechanisms in different species are recommended.

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In the present study, an attempt was made to produce a precise 3D image of a tomato canopy using a portable high-resolution scanning lidar. The tomato canopy was scanned by the lidar from three positions surrounding it. Through the scanning, the point cloud data of the canopy were obtained and they were co-registered. Then, points corresponding to leaves were extracted and converted into polygon images. From the polygon images, leaf areas were accurately estimated with a mean absolute percent error of 4.6%. Vertical profile of leaf area density (LAD) and leaf area index (LAI) could be also estimated by summing up each leaf area derived from the polygon images. Leaf inclination angle could be also estimated from the 3-D polygon image. It was shown that leaf inclination angles had different values at each part of a leaf.

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Spatio-temporal effects of herbicide including 3-(3,4 dichlorophenyl)-1,1-dimethylurea (DCMU) on a whole melon (Cucumis melo L.) plant were three-dimensionally monitored using combined range and chlorophyll a fluorescence imaging. The herbicide was treated to soil in a pot and the changes in chlorophyll a fluorescence images of the plant were captured over time. The time series of chlorophyll fluorescence images were combined with 3D polygon model of the whole plant taken by a high-resolution portable scanning lidar. From the produced 3D chlorophyll fluorescence model, it was observed that the increase of chlorophyll fluorescence appeared along veins of leaves and gradually expanded to mesophylls. In addition, it was found by detailed analysis of the images that the invisible herbicide injury on the mature leaves occurred earlier and more severely than on the young and old leaves. The distance from veins, whole leaf area and leaf inclination influenced the extent of the injury within the leaves. These results indicated difference in uptake of herbicide in the plant from soil depends on structural parameters of leaves and the microenvironments as well as leaf age. The findings showed that 3D monitoring using combined range and chlorophyll a fluorescence imaging can be utilised for understanding spatio-temporal changes of herbicide effects on a whole plant.

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Seasonal change of vertical leaf area density (LAD) profiles of woody canopy broad-leaved trees (Zelkova serrata [Thunberg] Makino) was estimated using 3D portable scanning light detection and ranging (LIDAR) imaging. First, 3D point cloud data for the canopy were collected using a portable LIDAR in spring, summer, autumn and winter. For data collection, the canopy was evenly scanned by the LIDAR from three positions 10 m above the ground. Next, the vertical LAD profile in each season was computed from the LIDAR data using the voxel-based canopy profiling (VCP) method. For the computation, non-photosynthetic tissues were eliminated using the LIDAR data obtained during winter. Influence of leaf inclination angle (LIA) on LAD estimation was corrected by LIA data measured by a high-resolution portable scanning LIDAR. The resultant profiles showed that LAD values tended to increase at the upper canopy from spring to summer and decrease at the middle and lower canopy from summer to autumn. Moreover, LIDAR-derived LIA distributions were compared among different seasons. LIA showed an even distribution in spring but changed to a planophile distribution in summer. In autumn, the angles in the <30° class decreased and those between the 30 and 40°classes increased.

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By introducing a reference dry leaf (a leaf without transpiration), a formerly proposed plant transpiration transfer coefficient (hat) was applied to detect environmental stress caused by water shortage and high temperature on melon, tomato and lettuce plants under various conditions. Results showed that there were obvious differences between leaf temperature, dry reference leaf temperature and air temperature. The proposed coefficient hat could integrate the three temperatures and quantitatively evaluate the environmental stress of plants. Experimental results showed that the water stress of melon plants under two irrigation treatments was clearly distinguished by using the coefficient. The water stress of a tomato plant as the soil dried under a controlled environmental condition was sensitively detected by using hat. A linear relationship between hat and conventional crop water stress index was revealed with a regression determination coefficient R2 = 0.97. Further, hat was used to detect the heat stress of lettuce plants under high air temperature conditions (28.7°C) with three root temperature treatments (21.5, 25.9 and 29.5°C). The canopy temperature under these treatments was respectively 26.44, 27.15 and 27.46°C and the corresponding hat value was -1.11, -0.74 and -0.59. Heat stress was also sensitively detected using hat. The main advantage of hat is its simplicity for use in infrared applications.

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We analyzed the chlorophyll fluorescence parameters in a 3D cellular arrangement in vivo by using a modified Nipkow disk-type confocal laser scanning microscope (CLSM). We first defined the 3D values of Phi(PSII) (photochemical yield of PSII) and NPQ (non-photochemical quenching) in mesophyll, epidermal and guard cell chloroplasts from the leaf surface to several tens of microns in depth. We also used this CLSM method to analyze the relationships between actinic light intensity and the chlorophyll fluorescence parameters for Boston fern and broad bean leaf specimens. As the actinic light intensity increased, the mean Phi(PSII) values decreased and the NPQ values increased in all chloroplasts of Boston fern and broad bean leaf. These values differed with cell type and species. The Boston fern chloroplasts had lower Phi(PSII) values than the broad bean chloroplasts, and vice versa for the NPQ values. The Phi(PSII) values of Boston fern chloroplasts decreased in the order mesophyll, epidermal and guard cell chloroplasts. The NPQ values decreased in the order guard cell, mesophyll and epidermal chloroplasts, except at 12 micromol m(-2) s(-1) actinic light, when the mesophyll value was slightly lower than that of the epidermis. The trend in the Phi(PSII) and NPQ values of broad bean mesophyll and guard cell chloroplasts was opposite to that of Boston fern chloroplasts. As 3D CLSM can provide the Phi(PSII) and NPQ values of each chloroplast in a 3D cellular arrangement, this method has potential for investigating differences in the functions of chloroplasts in vivo.

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Web spiders are considered to have expanded their habitats from dim to bright environments during the evolutionary history. Because they are sedentary predators exposed to the sun, they may have developed a suite of adaptive traits to cope with thermal stress. We examined the critical thermal maximum, spectral reflectance of solar energy by the body surface, and surface-volume ratio (SVR) for 11 spider species. Analysis of the four genera having a pair of species inhabiting both bright and dim environments showed that species in bright environments exhibited higher lethal temperatures, but spectral reflectance and SVR did not differ. Independent contrasts using the 11 species indicated that critical thermal maximum was positively correlated with spectral reflectance and spectral reflectance was negatively correlated with SVR. These results suggest that physiological tolerance to high temperatures and a biophysical mechanism to reduce heat gain evolved jointly during the history of habitat expansion in araneoid spiders.

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A 15-membered macrolide, iriomoteolide-3a (1), with an allyl epoxide has been isolated from a marine benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was assigned by detailed analyses of 2D NMR data. Relative and absolute configurations were elucidated on the basis of conformational studies of 1 and its acetonide (2) and modified Mosher's method of 1, respectively. Iriomoteolide-3a (1) and the acetonide (2) exhibited potently cytotoxic activity against antitumor cells.

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Factors that contribute to the accuracy of estimating woody canopy's leaf area density (LAD) using 3D portable lidar imaging were investigated. The 3D point cloud data for a Japanese zelkova canopy [Zelkova serrata (Thunberg) Makino] were collected using a portable scanning lidar from several points established on the ground and at 10 m above the ground. The LAD profiles were computed using voxel-based canopy profiling (VCP). The best LAD results [a root-mean-square error (RMSE) of 0.21 m(2) m(-3)] for the measurement plot (corresponding to an absolute LAI error of 9.5%) were obtained by compositing the ground-level and 10 m measurements. The factors that most strongly affected estimation accuracy included the presence of non-photosynthetic tissues, distribution of leaf inclination angles, number (N) of incident laser beams in each region within the canopy, and G(theta(m)) (the mean projection of a unit leaf area on a plane perpendicular to the direction of the laser beam at the measurement zenith angle of theta(m)). The influences of non-photosynthetic tissues and leaf inclination angle on the estimates amounted to 4.2-32.7% and 7.2-94.2%, respectively. The RMSE of the LAD estimations was expressed using a function of N and G(theta(m)).

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A potent cytotoxic 20-membered macrolide, iriomoteolide-1a (1), has been isolated from a benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was elucidated on the basis of detailed analyses of 2-D NMR data. The relative and absolute stereochemistries were assigned by the combination of conformational analyses using NMR data and modified Mosher's method of 1.

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A passive light microscope system has been developed, capable of reconstructing an extended-focus 3-D cell-level image of chlorophyll fluorescence and Phi(PSII) of intact attached leaves using a limited number of focal plane images of chlorophyll fluorescence. Using this system, the relationships between the depth of the mesophyll cells in spongy tissue and the intensity of the chlorophyll fluorescence and the Phi(PSII) were investigated in sunflower leaves exposed to 300 ppb ozone for 12 h at a PPFD of 300 micromol m(-2) s(-1) actinic light. After ozone exposure, fluorescence intensity (F) largely decreased in the cells just under the epidermal cells (within approximately 20 microm of the epidermal cells), but the sites where fluorescence intensity decreased had no relationship to the position of the stomata. By contrast, the distribution of Phi(PSII) showed no change after the ozone exposure. These findings suggest that ozone-induced inhibition occurs in the cells just under the epidermal cells by reducing the light absorption of the chloroplasts, while the operating quantum efficiency of PSII photochemistry is maintained.

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