Leaf Position Research Articles

In vitro antioxidant activity and antidiabetic potential of five spiral ginger (Costus speciosus (J. Koenig) Sm.) populations available in Sri Lanka

Diabetes mellitus has caused millions of deaths worldwide. Costus speciosus leaves are consumed as a green leafy vegetable in Sri Lanka due to their claimed medicinal properties including hypoglycemic effect. This work aimed mainly to evaluate the antioxidant and antidiabetic potential of the five distinct C. speciosus leaves populations (P1, P2, P3, P4, and P5) available in Sri Lanka for future therapeutic food applications. Methanol extracts and hot water infusions of C. speciosus leaves were obtained and the total phenolic content, flavonoid content, total antioxidant capacity, and DPPH radical scavenging activity were determined by colorimetric assays. Moreover, in vitro antidiabetic activity was assessed using alpha-glucosidase and alpha-amylase enzyme inhibition assays. There was a remarkable variation in the functional properties among the five populations of C. speciosus as well as among the five different leaf positions from the apical to the basal part of the twig. The highest total phenolic content, DPPH radical scavenging activity, and total antioxidant capacity were observed in methanol leaf extracts of P3 as 7.49 ± 0.21 mg GAE g-1, 91.57 ± 0.08%, and 10.39 ± 0.50 mg AAE g-1 respectively. Leaf bud contained significantly (p < 0.05) the highest total phenolic content and DPPH radical scavenging activity than the other leaf positions. C. speciosus population 1 exhibited significantly (p < 0.05) the highest antidiabetic activity in terms of alpha-glucosidase enzyme inhibition, with an IC50 value of 2.57 mg mL−1 compared to the standard acarbose (12.85 mg mL−1). In the conclusion of the study, C. specious variety available in Sri Lanka can be considered as a potential candidate for therapeutic food applications.

Phototropin phosphorylation of ROOT PHOTOTROPISM 2 and its role in mediating phototropism, leaf positioning, and chloroplast accumulation movement in Arabidopsis.

Directional movements impact the ability of plants to respond and adjust their growth accordingly to the prevailing light environment. The plasma-membrane associated protein, ROOT PHOTOTROPISM 2 (RPT2) is a key signalling component involved in chloroplast accumulation movement, leaf positioning, and phototropism, all of which are regulated redundantly by the ultraviolet/blue light-activated AGC kinases phototropin 1 and 2 (phot1 and phot2). We recently demonstrated that members of the NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3)/RPT2-like (NRL) family in Arabidopsis thaliana, including RPT2, are directly phosphorylated by phot1. However, whether RPT2 is a substrate for phot2, and the biological significance of phot phosphorylation of RPT2 remains to be determined. Here, we show that RPT2 is phosphorylated by both phot1 and phot2 at a conserved serine residue (S591) within the C-terminal region of the protein. Blue light triggered the association of 14-3-3 proteins with RPT2 consistent with S591 acting as a 14-3-3 binding site. Mutation of S591 had no effect on the plasma membrane localization of RPT2 but reduced its functionality for leafpositioning and phototropism. Moreover, our findings indicate that S591 phosphorylation within the C-terminus of RPT2 is required for chloroplast accumulation movement to low level blue light. Taken together, these findings further highlight the importance of the C-terminal region of NRL proteins and how its phosphorylation contributes to phot receptor signalling in plants.

Impact of electronic portal image quality on Elekta AQUA® collimator isocenter.

The collimator radiation isocenter position determined in AQUA® v3.0 [Elekta AB, Stockholm, Sweden] software test "MLC Leaf and Jaw Position" was independently validated using an in-house MATLAB [Natick, MA: The MathWorks Inc.] script. The AQUA test determines radiation isocenter using the mean field center of nine 4 cm × 4 cm electronic portal imager (EPID) exposures at equidistant collimator angles. Impact of EPID image quality on AQUA reported isocenter for thirteen Elekta linear accelerators with Agility MLC heads were evaluated. Of the thirteen, three had visually and quantitatively identifiable artifacts. For the ten good EPID's there was a systematic 0.25 mm offset of the MATLAB calculated mean field center relative to AQUA in the X-axis and Y-axis. This corresponds to one image pixel and was found to be due to differences in software co-ordinate convention. After subtracting this offset there was no significant difference in AQUA and MATLAB calculated isocenter. For the three machines with poor image quality there was a demonstrated variation in AQUA calculated field center and therefore radiation isocenter relative to MATLAB. Restricting the region of interest (ROI) in AQUA software to only the irradiated section of the EPID brought AQUA and MATLAB result for these three machines into agreement.

Methodology of stem water potential measurement on hedgerow olive orchards

Aim of study:To evaluate the effect of leaf covering, leaf position, leaf age, time and sample size in measurements of stem water potential (Ψstem) in olive hedgerow orchards. Area of study: The experimental orchards were located in the Centre of Spain (Toledo) Material and methods: Midday Ψstem was measured using a pressure chamber in two super-intensive olive hedgerow orchards subjected to various water status. Main results: Measurements were taken at solar noon on shaded leaves at mid canopy height following at least 1 hour of covering. Such measurements on 5 trees were sufficient to define the water status of individual homogeneous irrigation blocks. This combination of techniques is essential for repeatable measurements of Ψstem required to establish critical irrigation points and manage deficit irrigation strategies seeking to control vegetative growth and reduce water use with minimal effect on oil yield in olive hedgerow orchards and maximum oil quality. Part of our results weren’t previously reported: 1) Covering leaves with aluminium doesn’t completely stop transpiration and leaves must be covered and located in the shaded part of the canopy. 2) Ψstem depends on leaf height on olive hedgerow. 3) Ψstem of young leaves was less variable than in older ones. 4) Ψstem at solar noon presented larger differences with previous hours than later. Research highlights: Leaves for measurements of stem water potential must be previously covered and located in the middle height of the shaded part of the canopy.

Pedicel colour does not separate Epipactis dunensis (Dune Helleborine) from E. ‘sancta’ (Lindisfarne Helleborine) (Orchidaceae)

The characters which supposedly differentiate the narrow endemic Epipactis sancta (Delforge) Delforge on Lindisfarne (north-east England) from ‘Tyne’ and west coast (type) populations of Epipactis dunensis (T. &amp; T.A. Stephenson) Godfery are examined. Lindisfarne plants vary for purple staining of the pedicel, while ‘Tyne’ populations and at least some west coast plants lack this character. There is no significant difference between ‘Tyne’ and Lindisfarne populations for the relative length of the inflorescence (position of uppermost leaf). It is shown that other supposed differences are apparently trivial. It is considered that minor differences in sequence in chloroplast DNA between the populations do not in themselves suggest that E. sancta deserves specific rank. It is concluded that the Lindisfarne population is best regarded as E. dunensis.

A mutation in CsABCB19 encoding an ATP-binding cassette auxin transporter leads to erect and compact leaf architecture in cucumber (Cucumis sativus L.)

Leaf architecture, including leaf position and leaf morphology, is a critical component of plant architecture that directly determines plant appearance, photosynthetic utilization, and ultimate productivity. The mechanisms regulating leaf petiole angle and leaf flatness in cucumber remain unclear. In this study, we identified an erect and compact leaf architecture mutant (ecla) from an EMS (ethyl methanesulfonate) -mutagenized cucumber population, which exhibited erect petioles and crinkled leaves. Histological examination revealed significant phenotypic variation in ecla was associated with asymmetric cell expansion. MutMap sequencing combined with genetic mapping revealed that CsaV3_5G037960 is the causative gene for the ecla mutant phenotype. Through protein sequence alignment and Arabidopsis genetic complementation, we identified this gene as a functional direct homolog encoding the ATP-binding cassette transporter AtABCB19, hence named CsABCB19. A nonsynonymous mutation in the eleventh exon of CsABCB19 leads to premature termination of translation. The expression level of CsABCB19 in the ecla mutant was significantly reduced in all tissues compared to the wild type (WT). Transcriptome analysis revealed that auxin and polarity-related genes were significantly differentially expressed in mutant petioles and leaves, compared with those in WT. Auxin assay and exogenous treatment further demonstrated that CsABCB19 regulates leaf architecture by mediating auxin accumulation and transport. Our research is the first report describing the role of the ABCB19 transporter protein in auxin transport controlling cucumber leaf development. Furthermore, this study provides recent insights into the genetic mechanisms conferring morphological diversity and regulation of petiole angle and leaf flattening. Data availabilityThe RNA-seq data in this study have been deposited in the NCBI SRA under BioProject accession number PRJNA874548.

Performance of a Full-Scale Upstream MAPS-Based Verification Device for Radiotherapy.

Intensity-modulated radiotherapy is a widely used technique for accurately targeting cancerous tumours in difficult locations using dynamically shaped beams. This is ideally accompanied by real-time independent verification. Monolithic active pixel sensors are a viable candidate for providing upstream beam monitoring during treatment. We have already demonstrated that a Monolithic Active Pixel Sensor (MAPS)-based system can fulfill all clinical requirements except for the minimum required size. Here, we report the performance of a large-scale demonstrator system consisting of a matrix of 2 × 2 sensors, which is large enough to cover almost all radiotherapy treatment fields when affixed to the shadow tray of the LINAC head. When building a matrix structure, a small dead area is inevitable. Here, we report that with a newly developed position algorithm, leaf positions can be reconstructed over the entire range with a position resolution of below ∼200 μm in the centre of the sensor, which worsens to just below 300 μm in the middle of the gap between two sensors. A leaf position resolution below 300 μm results in a dose error below 2%, which is good enough for clinical deployment.

Functional Mapping of Genes Modulating Plant Shade Avoidance Using Leaf Traits.

Shade avoidance syndrome (SAS) refers to a set of plant responses that increases light capture in dense stands. This process is crucial for plants in natural and agricultural environments as they compete for resources and avoid suboptimal conditions. Although the molecular, biochemical, and physiological mechanisms underlying the SAS response have been extensively studied, the genetic basis of developmental variation in leaves in regard to leaf area, petiole length, and leaf length (i.e., their allometric relationships) remains unresolved. In this study, with the recombinant inbred line (RIL) population, the developmental traits of leaves of Arabidopsis were investigated under two growth density conditions (high- and low-density plantings). The observed changes were then reconstructed digitally, and their allometric relationships were modelled. Taking the genome-wide association analysis, the SNP genotype and the dynamic phenotype of the leaf from both densities were combined to explore the allometry QTLs. Under different densities, leaf change phenotype was analyzed from two core ecological scenarios: (i) the allometric change of the leaf area with leaf length, and (ii) the change of the leaf length with petiole length. QTLs modulating these two scenarios were characterized as 'leaf shape QTLs' and 'leaf position QTLs'. With functional mapping, results showed a total of 30 and 24 significant SNPs for shapeQTLs and positionQTLs, respectively. By annotation, immune pathway genes, photosensory receptor genes, and phytohormone genes were identified to be involved in the SAS response. Interestingly, genes modulating the immune pathway and salt tolerance, i.e., systemic acquired resistance (SAR) regulatory proteins (MININ-1-related) and salt tolerance homologs (STH), were reported to mediate the SAS response. By dissecting and comparing QTL effects from low- and high-density conditions, our results elucidate the genetic control of leaf formation in the context of the SAS response. The mechanism with leaf development × density interaction can further aid the development of density-tolerant crop varieties for agricultural practices.

Differential sensitivities of photosynthetic processes and carbon loss mechanisms govern N-induced variation in net carbon assimilation rate for field-grown cotton.

Nitrogen (N) deficiency limits the net carbon assimilation rate (AN), but the relative N sensitivities of photosynthetic component processes and carbon loss mechanisms remain relatively unexplored for field-grown cotton. Therefore, the objective of the current study was to define the relative sensitivity of individual physiological processes driving N deficiency-induced declines in AN for field-grown cotton. Among the potential diffusional limitations evaluated, mesophyll conductance was the only parameter substantially reduced by N deficiency, but this did not affect CO2 availability in the chloroplast. A number of metabolic processes were negatively impacted by N deficiency, and these effects were more pronounced at lower leaf positions in the cotton canopy. Ribulose bisphosphate (RuBP) regeneration and carboxylation, AN, and gross photosynthesis were the most sensitive metabolic processes to N deficiency, whereas photosynthetic electron transport processes, electron flux to photorespiration, and dark respiration exhibited intermediate sensitivity to N deficiency. Among thylakoid-specific processes, the quantum yield of PSI end electron acceptor reduction was the most sensitive process to N deficiency. It was concluded that AN is primarily limited by Rubisco carboxylation and RuBP regeneration under N deficiency in field-grown cotton, and the differential N sensitivities of the photosynthetic process and carbon loss mechanisms contributed significantly to photosynthetic declines.

Determining an Appropriate Leaf Position to Establish Norms of Diagnosis and Recommendation Integrated System for Ratoon Pineapple

Determining an Appropriate Leaf Position to Establish Norms of Diagnosis and Recommendation Integrated System for Ratoon Pineapple

Challenges of using leaves as a biomonitoring system to assess airborne microplastic deposition on urban tree canopies

Monitoring microplastic concentrations in the atmosphere is critical for assessing their inhalation risk in urban areas and other ecological impacts on the natural environment. To assess these risks, leaves in tree canopies could be used as a biomonitoring system, but this requires knowledge of the potential variability of microplastic concentrations based on leaf properties and position in the tree. This study aims to quantify this potential variability by analyzing the concentration of airborne microplastics on leaves in Los Angeles as a function of leaf height, leaf surface hydrophobicity, and land use. Microplastic concentrations on leaves varied between 0.14 and 25 particles(n) cm−2, but the concentration peaked within 0.6–1.2 m height above ground, indicating the position of the leaf above the ground could matter. Microplastic concentrations varied significantly between leaf types indicating leaf surface properties could influence the retention of microplastics. Contact angle measurements revealed that the hydrophilicity of leaves had a weak correlation with microplastic concentrations on leaves, indicating other factors such as surface roughness or leaf features could be important for microplastic retention. Land-use type did not affect microplastic concentration. The results confirmed a high uncertainty in predicting microplastic concentration on leaves in the urban canopy, which limits their ability to be used as biomonitoring systems for microplastic pollution in urban areas.

Yield and nutritional quality of soil-cultivated crisphead lettuce (Lactuca sativa L. var. capitata) and corn salad (Valerianella spp.) harvested at different growing periods.

Crisphead lettuce and corn salad varieties were grown during different growing seasons in the greenhouse or in the field under intensive tillage. They were evaluated for agronomic and nutritional quality to determine the influence of growing period, variety, and in the case of lettuce, leaf position (inner, middle, and outer leaf) on total and marketable yield, color parameters, relative chlorophyll, total sugars, isovaleric acid, total phenolic content (TPC), and multielement composition. Significant differences were found among total yield, color parameters (L*, b*, c*, and hue), and relative chlorophyll for crisphead lettuce, and color parameters (L*, a*, b*, c*, and hue) and relative chlorophyll for corn salad varieties. Relative chlorophyll was strongly correlated with most color parameters. The growing period affected yield, relative chlorophyll, TPC, total sugars, isovaleric acid, and multielement composition for corn salad, and the color parameter a* and relative chlorophyll for crisphead lettuce. The position of lettuce leaves had a significant effect on TPC, total sugars, and multielement composition. In addition, this study confirmed that farmers and consumers should pay attention to nutritional quality when selecting different lettuce and corn salad varieties.

Cold priming improves chilling resistance in wheat seedlings: Changing of photosystem II imprints during recovery from priming

Chilling stress oriented from frequent extreme events has seriously depressed growth and productivity of wheat. Cold priming can effectively improve cold tolerance of crops. However, it is still unclear about the changes of stress memory imprints during recovery from priming and the potential function of the imprints on improved cold tolerance. Here we subjected wheat plants to cold priming (10 °C/6 °C, 1 d) at the trifoliate stage, and then to chilling stresses (2 °C/0 °C, 1 d) at 3, 6, 9, 12, 15 and 18 days of recovery from priming, respectively. Compared with non-primed plants (NL), primed plants (PL) showed the most obvious resistance phenotype at 9 days after priming. Its terminal spreading leaves exhibit temporally specific physiological memory and persistent a high photochemical quenching capacity of photosystem II after priming. In addition, it appeared faster photosynthetic performance in the post-stress rewarming phase during 3–12 days after priming. Further analysis of different leaf positions revealed that priming increased light energy absorption by the augmented antennal pigments content and synthesis of light-harvesting proteins, and a higher percentage of primary and secondary quinone electron acceptors (QAQB) active reaction centers (RCs) which enhanced energy capture and transfer performance in primed control plants (PC). Meanwhile, the increased antenna pigments in PC indirectly affected PL. Compared with NL, priming increased electron flux into the inter-system by alleviating the degradation of antenna pigments and increased Photosystem II Subunit S (PsbS) gene expression to promote the occurrence of non-photochemical quenching (NPQ), lowered the excitation pressure per RC, and increased the percentage of QA-RCs, it finally improved the light energy absorption and utilization capacity in PL. In summary, priming-induced memory is mainly present in primed leaves (3rd and 4th leaves during R6-R15) and diminishes with spatial and temporal changes, it exists even no obvious difference in phenotype. This study contributes to a deeper understanding of the long-term effects of fluctuating temperatures on the plant.

A method for adjusting MLC leaf positions outside a reference region for VMAT plans in a commercial treatment planning system.

Multileaf collimators (MLC) leaf positions in a volumetric modulated arc therapy (VMAT) plan is determined from inverse treatment planning process. On the isocenter plane, leaf projections should not be set too far out of projected PTV boundary. In this study we developed an automatic method of adjusting leaf positions outside a reference region of interest (ROI) for VMAT plans generated in Pinnacle treatment planning system (TPS). The proposed method consisted of a Pinnacle script and a Python program. It checked each MLC leaf position for all control points in a VMAT arc relative to a reference ROI created by adding a small margin to PTV. For leaves opened outside the reference ROI, the method adjusted their positions to reduce dose to normal tissue while maintaining PTV coverage and satisfying leaf position constraints. The deliverability and dose accuracy of the method was verified by applying it to 15 VMAT plans which were delivered in five different linacs in our department. Dosimetric improvement of the proposed method was analyzed for another group of 16 randomly selected VMAT plans. The average gamma passing rate using a 3%/3 mm criteria for the verification group of VMAT plans was 98.3% and all passing rates were above our internal passing threshold. Dosimetric improvement was observed for the evaluation group of VMAT plans. The method can improve normal tissue protection for VMAT plans. It can be safely applied in routine clinic work.

Comparisons of the stomatal conductance and electron transport rate of three Japanese rice cultivars including Himenorin in Ehime Prefecture

This study focused on stomatal conductance (gs) and electron transport rate (ETR) as one possible approach to the mechanisms of controlling canopy temperature and photosynthetic traits in rice. Three Japanese rice cultivars, Koshihikari (KH), Nikomaru (NM), and the new cultivar Himenorin (HR) developed in Ehime Prefecture were selected for the experiment. From the uppermost to the fifth leaves of five or more rice plants of each cultivar, gs and ETR were measured in situ using a handheld porometer/fluorometer. The results revealed the highest gs in HR among the three cultivars in all leaf positions from before the flag leaf extension until the maturity stage, which could be regarded as one of the advantageous mechanisms for moderating the thermal condition of the canopy with larger transpiration and supporting a higher photosynthetic level. The ETR of HR was highest among the three cultivars in most leaf positions from the heading stage to the maturity stage, which could be expected to maintain a higher photosynthetic level. These traits of gs and ETR in HR compared with NM and KH could be assessed as possible synergistic mechanisms for higher production and quality of rice with higher photosynthetic potential.

Generating 3D Multispectral Point Clouds of Plants with Fusion of Snapshot Spectral and RGB-D Images.

Accurate and high-throughput plant phenotyping is important for accelerating crop breeding. Spectral imaging that can acquire both spectral and spatial information of plants related to structural, biochemical, and physiological traits becomes one of the popular phenotyping techniques. However, close-range spectral imaging of plants could be highly affected by the complex plant structure and illumination conditions, which becomes one of the main challenges for close-range plant phenotyping. In this study, we proposed a new method for generating high-quality plant 3-dimensional multispectral point clouds. Speeded-Up Robust Features and Demons was used for fusing depth and snapshot spectral images acquired at close range. A reflectance correction method for plant spectral images based on hemisphere references combined with artificial neural network was developed for eliminating the illumination effects. The proposed Speeded-Up Robust Features and Demons achieved an average structural similarity index measure of 0.931, outperforming the classic approaches with an average structural similarity index measure of 0.889 in RGB and snapshot spectral image registration. The distribution of digital number values of the references at different positions and orientations was simulated using artificial neural network with the determination coefficient (R 2) of 0.962 and root mean squared error of 0.036. Compared with the ground truth measured by ASD spectrometer, the average root mean squared error of the reflectance spectra before and after reflectance correction at different leaf positions decreased by 78.0%. For the same leaf position, the average Euclidean distances between the multiview reflectance spectra decreased by 60.7%. Our results indicate that the proposed method achieves a good performance in generating plant 3-dimensional multispectral point clouds, which is promising for close-range plant phenotyping.

Study on the flowering in rice plant (Oryza sativa cv. OM5451)

Introduction: The consumption of rice is rising in response to worldwide population development. The purpose of this study was to determine the stages of plant development, specifically the transition stage from panicle initiation to the flowering stage, which determines the number of spikelets per branch. In addition, this research studied the changes in physiology and morphology during the flowering development of rice in a garden. Methods: Plant height, number of leaves, number of tillers, and flowering time were all measured. Plant growth regulators such as cytokinin, auxin, gibberellic acid (GA), and acid abscisic (ABA) in the apical shoot at different stages of flower development were analyzed. Results: The activities of indole acetic acid (IAA), zeatin, and gibberellins in the apical shoot of the stem elongation stage are higher than those in plants of the panicle initiation stage. At the flowering stage, the rates of photosynthesis and respiration of the leaves at positions 1, 2, and 3 were higher than those of the other leaves. In addition, photosynthetic pigments at leaf positions 2, 3, and 4 were higher than those at positions 1 and 3. Conclusion: The results show that the relationship between changes in morphological, physiological, and biochemical indicators during the rice growth stages was discussed.

Spatiotemporal Heterogeneity of Chlorophyll Content and Fluorescence Response within Rice (Oryza sativa L.) Canopies under Different Cadmium Stress

The spatiotemporal heterogeneity of rice canopy leaves at different leaf positions is very important for non-destructive monitoring under Cadmium (Cd) stress, and is one of the key problems that need to be solved urgently in modern agriculture. This study aims to explore the temporal and spatial heterogeneity of chlorophyll content and fluorescence in rice canopy leaves under different Cd stress concentrations. The responses of the relative chlorophyll content (SPAD) and Chlorophyll fluorescence (ChlF) parameters to Cd stress in the tillering, heading, and filling stages were analyzed through pot experiments with three Cd concentrations: 0.20 mg·kg−1 (CK), 0.60 mg·kg−1 (Cd1), and 1.60 mg·kg−1 (Cd2). Results showed that the canopy leaf SPAD value increased with increasing Cd concentration. Compared with CK, the leaf SPAD value in the Cd1 and Cd2 treatments were 1.91–3.45% and 5.52–12.01% lower, respectively. The SPAD value of the lower leaves was higher in the tillering stage, while the SPAD value of the upper leaves was higher in the heading and filling stages. The non-photochemical quenching coefficient (NPQ) of the third leaf (D3), the initial fluorescence yield (Fo) of the second leaf (D2), and the maximum photochemical efficiency (Fv/Fm) of photosystem II (PSII) in the tillering stage; the NPQ, Fo, and Fv/Fm of the D3 in the heading stage; and the NPQ, Fo, Fv/Fm, and Fv/Fm of the D2 in the filling stage were more sensitive to Cd stress than the other leaves and ChlF parameters.

Automatic Disease Detection of Basal Stem Rot Using Deep Learning and Hyperspectral Imaging

Basal Stem Rot (BSR), a disease caused by Ganoderma boninense (G. boninense), has posed a significant concern for the oil palm industry, particularly in Southeast Asia, as it has the potential to cause substantial economic losses. The breeding programme is currently searching for G. boninense-resistant planting materials, which has necessitated intense manual screening in the nursery to track the progression of disease development in response to different treatments. The combination of hyperspectral image and machine learning approaches has a high detection potential for BSR. However, manual feature selection is still required to construct a detection model. Therefore, the objective of this study is to establish an automatic BSR detection at the seedling stage using a pre-trained deep learning model and hyperspectral images. The aerial view image of an oil palm seedling is divided into three regions in order to determine if there is any substantial spectral change across leaf positions. To investigate if the background images affect the performance of the detection, segmented images of the plant seedling have been automatically generated using a Mask Region-based Convolutional Neural Network (RCNN). Consequently, three models are utilised to detect BSR: a convolutional neural network that is 16 layers deep (VGG16) model trained on a segmented image; and VGG16 and Mask RCNN models both trained on the original images. The results indicate that the VGG16 model trained with the original images at 938 nm wavelength performed the best in terms of accuracy (91.93%), precision (94.32%), recall (89.26%), and F1 score (91.72%). This method revealed that users may detect BSR automatically without having to manually extract image attributes before detection.

Dynamic of Fluorescence Emissions at O2A and O2B Telluric Absorption Bands in Forested Areas with Seasonal APAR and GPP Variations

We measured dynamics of solar-induced chlorophyll fluorescence at telluric oxygen absorption bands O2A and O2B in evergreen spruce and deciduous beech forests. Seasonal variations in fluorescence emissions were compared with NDVI. Daily changes in fluorescence emissions were compared with canopy shadow fraction (αS) dynamics, which showed impact of branch and leaf positions on detected fluorescence signals based on comparison with canopy height model. Absorbed photosynthetically active radiation (APAR) was recognized as a large determinant of fluorescence changes within the O2A band (SIFA), with R2 &gt; 0.68. Fluorescence within the O2B band was more directly linked to NDVI. Although, the seasonal dynamics of fluorescence within the O2B band (SIFB) were similar to SIFA in the spruce forest. In the beech forest, SIFB showed different seasonal dynamics as compared with SIFA. SIFA in the spruce forest showed a relationship to gross primary productivity (GPP), with R2 = 0.48, and a relationship of R2 = 0.37 was estimated for the SIFA-GPP connection in the beech forest. SIFB was better linked to seasonal GPP in the beech forest, but with a negative slope in the relationship with R2 = 0.61. We have shown that measurements of passive fluorescence signals at telluric oxygen absorption bands can contribute to understanding to photosynthesis processes in forest canopies.