Evaluating the dendroclimatological potential of blue intensity on multiple conifer species from Australasia

We evaluate a range of blue intensity (BI) tree-ring parameters in eight conifer species (12 sites) from Tasmania and New Zealand for their dendroclimatic potential, and as surrogate wood anatomical proxies. Using a dataset of ca. 10–15 trees per site, we measured earlywood maximum blue reflectance intensity (EWB), latewood minimum blue reflectance intensity (LWB) and the associated delta blue intensity (DB) parameter for dendrochronological analysis. No resin extraction was performed, impacting low frequency trends. Therefore, we focused only on the high frequency signal by detrending all tree-ring and climate data using a 20-year cubic smoothing spline. All BI parameters express low relative variance and weak signal strength compared to ring-width. Correlation analysis and principal component regression experiments identified a weak and variable climate response for most ring-width chronologies. However, for most sites, the EWB data, despite weak signal strength, expressed strong calibrations with summer temperatures. Significant correlations for LWB were also noted, but the sign of the relationship for most species is opposite to that reported for all conifer species in the Northern Hemisphere. DB performed well for the Tasmanian sites but explained minimal temperature variance in New Zealand. Using the full multi-species/parameter network, excellent summer temperature calibration was identified for both Tasmania and New Zealand ranging from 52 % to 78 % explained variance, with equally robust independent validation (Coefficient of Efficiency = 0.41 to 0.77). Comparison of the Tasmanian BI reconstruction with a wood anatomical reconstruction shows that these parameters record essentially the same strong high frequency summer temperature signal. Despite these excellent results, a substantial challenge exists with the capture of potential secular scale climate trends. Although DB, band-pass and other signal processing methods may help with this issue, substantially more experimentation is needed in conjunction with comparative analysis with ring density and quantitative WA measurements.

Different types of macular telangiectasia in two eyes of a patient

Purpose: To report a case of macular telangiectasia (MacTel) showing the features of type 3 disease in one eye and type 2 disease in the other eye. Methods: Descriptive case report Case description: A 50-year-old well-controlled diabetic man presented with complaints of distorted vision in the right eye for the past 1 year. His best-corrected visual acuity in both eyes was 20/20, N6. His anterior segment findings were normal. The right eye fundus showed an irregular perifoveal greying and a localised dark patch temporally inside the perifoveal region. Few microaneurysms were seen on clinical examination. No hard exudates were noted. The left eye fundus showed a few microaneurysms with minimal perifoveal greying temporally. Imaging with confocal blue reflectance, fluorescein and optical coherence tomography angiography confirmed the diagnosis of MacTel type 3 in the right eye and type 2A stage 2 in the left eye with mild non-proliferative diabetic retinopathy in both eyes. Conclusion: This case raises the possibility that type 3 disease could be a progressive non-proliferative form of a pre-existing type 2 MacTel disease.

Differentiating between Nitrogen and Water Deficiency in Irrigated Maize Using a UAV-Based Multi-Spectral Camera

The objective of this research was to determine if canopy reflectance measured by an Unmanned Aerial Vehicle (UAV) equipped with a 5-band multi-spectral camera can differentiate between water and nitrogen (N) deficiency in irrigated maize. Crop reflectance was used to generate a Normalized Difference Red Edge (NDRE), Green Leaf Index (GLI), and a Blue Reflectance Index (BRI). These indices were then used in combination to categorize N and water stressed experimental units into a Combined Index (CI) indicating water-stressed, N-stressed, or non-stressed crops. The CI generated at blister (R2) successfully identified 90% of experimental treatments to the correct group but only identified 60% of treatments when generated at the 14th leaf stage (V14). The CI methodology was subsequently applied to two independent site-years where only N deficiency gradients were imposed. The CI was not successful at separating treatments at the validation sites, incorrectly identifying water stress where there was none. Among individual indices investigated, NDRE had the strongest relationship to grain yields (r2 = 0.62, p < 0.001) but a weaker linear relationship compared to the CI (r2 = 0.68, p < 0.005) where deficit irrigation treatments were imposed. At sites where irrigation was sufficient to meet crop water demand, NDRE (r2 = 0.63, p < 0.05) had a stronger relationship to grain yield compared to the CI (r2 = 0.41, p = 0.31). This study found that, under narrow cropping system circumstances, N and irrigation-induced differences in maize productivity can be differentiated in-season by a combination of reflectance indices, but that NDRE alone provides superior information under broader contexts.

A Novel Method for Estimating Nitrogen Stress in Plants Using Smartphones

For profits in crop production, it is important to ensure that plants are not subjected to nitrogen stress (NS). Methods to detect NS in plants are either time-consuming (e.g., laboratory analysis) or require expensive equipment (e.g., a chlorophyll meter). In this study, a smartphone-based index was developed for detecting NS in plants. The index can be measured in real time by capturing images and processing them on a smartphone with network connectivity. The index is calculated as the ratio of blue reflectance to the combined reflectance of blue, green, and red wavelengths. Our results indicated that the index was specific to NS and decreased with increasing stress exposure in plants. Further, the index was related to photosynthesis based on the path analysis of several physiological traits. Our results further indicate that index decreased in the NS treatment due to increase in reflectance of red and green (or yellow) wavelengths, thus it is likely related to loss of chlorophyll in plants. The index response was further validated in strawberry and hydrangea plants, with contrasting plant architecture and N requirement than petunia.

Light dependent morphological changes can tune light absorption in iridescent plant chloroplasts

Chloroplasts, the organelles responsible for photosynthesis in most plants and algae, exhibit a variety of morphological adaption strategies to changing light environments which can have important yet overlooked light scattering effects. This can be even more significant for iridoplasts, specialized chloroplasts whose tissue is arranged as a photonic multilayer producing a characteristic strong blue reflectance associated to a wavelength selective absorption enhancement relevant for photosynthesis.In this work, we study how the photonic properties of iridoplasts are affected by light induced dynamic changes using realistic data extracted from previous reports. Our results show a reflectance red-shift from blue to green under increasing light intensity. Consequently, the light absorption enhancement induced by the photonic nanostructure is also redshifted. We also show that the photonic properties are resilient to biologically realistic levels of disorder in the structure. We extended this analysis to another photonic nanostructure-containing chloroplast, known as a bisonoplast, and found similar results, pointing towards similar properties in different plant species. We finally found that all types of chloroplasts can tune light absorption depending on light conditions. In general, our study opens the door to understanding how dynamic morphologies in chloroplasts can affect light scattering and absorption.

Evaluation of inner retinal dimples and internal limiting membrane flap configuration after temporal inverted ILM flap technique

Purpose: To quantitatively evaluate structural changes associated with inner retinal dimples (IRDs) and qualitatively classify the internal limiting membrane (ILM) flap configuration after temporal inverted ILM flap technique using spectral domain optical coherence tomography (SD-OCT). Methods: Twenty-three eyes of 23 patients with successfully closed idiopathic, large (>400 μm) macular hole were enrolled. Patients were treated with pars plana vitrectomy followed by temporal inverted ILM flap technique. A complete ophthalmologic examination including cross sectional and en face OCT in addition to multicolor blue reflectance imaging of confocal scanning laser ophthalmoscopy (cSLO) was performed preoperatively and at postoperative month-12. The location, number, depth, and width of the IRDs were analyzed using blue reflectance images of multicolor cSLO and en face OCT. The ILM flap is also classified as smooth, wrinkled, and folded with en face OCT. Results: The mean number of IRDs visualized on en face OCT ( n = 23.08 ± 22.05) was statistically significantly higher compared with multicolor cSLO blue reflectance module (5.91 ± 10.58; p < 0.001). The mean depth of IRDs measured on en face OCT was 8.08 ± 3.1 μm (3–14 μm) which referred to the nerve fiber layer. The final visual acuity was associated with neither ILM flap configuration ( p = 0.408), nor number of the IRDs on en face OCT ( p = 0.112). Conclusion: En face OCT is a novel imaging modality that offers improved visualization and accuracy in identifying the features of the IRDs and the ILM flap. Additionally, it provides clear visualization of the vitreoretinal interface to distinguish whether ILM was peeled or not in the initial surgery.

Global 15-Meter Mosaic Derived from Simulated True-Color ASTER Imagery

This work proposes a new methodology to build an Earth-wide mosaic using high-spatial resolution ( 15 m ) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images in pseudo-true color. As ASTER originally misses a blue visible band, we have designed a cloud of artificial neural networks to estimate the ASTER blue reflectance from Level-1 data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the same satellite Terra platform. Next, the granules are radiometrically harmonized with a novel color-balancing method and seamlessly blended into a mosaic. We demonstrate that the proposed algorithms are robust enough to process several thousands of scenes acquired under very different temporal, spatial, and atmospheric conditions. Furthermore, the created mosaic fully preserves the ASTER fine structures across the various building steps. The proposed methodology and protocol are modular so that they can easily be adapted to similar sensors with enormous image libraries.

Phenotypic variation in Heliconius erato crosses shows that iridescent structural colour is sex-linked and controlled by multiple genes

Bright, highly reflective iridescent colours can be seen across nature and are produced by the scattering of light from nanostructures. Heliconius butterflies have been widely studied for their diversity and mimicry of wing colour patterns. Despite iridescence evolving multiple times in this genus, little is known about the genetic basis of the colour and the development of the structures which produce it. Heliconius erato can be found across Central and South America, but only races found in western Ecuador and Colombia have developed blue iridescent colour. Here, we use crosses between iridescent and non-iridescent races of H. erato to study phenotypic variation in the resulting F 2 generation. Using measurements of blue colour from photographs, we find that iridescent structural colour is a quantitative trait controlled by multiple genes, with strong evidence for loci on the Z sex chromosome. Iridescence is not linked to the Mendelian colour pattern locus that also segregates in these crosses (controlled by the gene cortex ). Small-angle X-ray scattering data show that spacing between longitudinal ridges on the scales, which affects the intensity of the blue reflectance, also varies quantitatively in F 2 crosses.