Light Adaptation Research Articles

Acute hyperglycemia compromises the responses of choroidal vessels using swept-source optical coherence tomography during dark and light adaptations.

To clarify the effects of acute hyperglycemia on the responses of choroidal structural components and vascularity index during light modulation in healthy participants using techniques including image binarization and artificial intelligence (AI) segmentation based on swept-source optical coherence tomography (SS-OCT). Twenty-four eyes of 24 healthy participants were imaged at different stages after ambient light, 40 min of dark adaptation, and 5 min of light adaptation in two imaging sessions: control and after receiving 75 g of oral glucose solution. The choroidal structural parameters, including luminal volume (LV), stromal volume (SV), total choroidal volume (TCV), and choroidal vascularity index (CVI) within a 6 mm area were determined using a custom algorithm based on image binarization and AI segmentation of SS-OCT. These measurements were compared among the conditions after adjusting for axial length, age to identify the differences. In the dark, CVI decreased (-0.36 ± 0.09%) significantly in acute hyperglycemia compared to the control condition. During the transition to ambient light, there was an increasing trend in the choroidal parameters compared with the control experiment. However, only TCV (0.38 ± 0.17 mm3) and LV (0.27 ± 0.10 mm3) showed a significant increase at the time point of 5 min after ambient light. Analysis of choroidal structural parameters and CVI based on SS-OCT images is a potentially powerful method to objectively reflect subtle changes in neurovascular coupling between the choroid and photoreceptor during dark adaptation.

Origin of Retinal Oscillatory Potentials in the Mouse, a Tool to Specifically Locate Retinal Damage

To determine the origin of oscillatory potentials (OPs), binocular electroretinogram (ERG) recordings were performed under light and dark adaptation on adult healthy C57BL/6J mice. In the experimental group, 1 μL of PBS was injected into the left eye, while the right eye was injected with 1 μL of PBS containing different agents: APB, GABA, Bicuculline, TPMPA, Glutamate, DNQX, Glycine, Strychnine, or HEPES. The OP response depends on the type of photoreceptors involved, showing their maximum response amplitude in the ERG induced by mixed rod/cone stimulation. The oscillatory components of the OPs were affected by the injected agents, with some drugs inducing the complete abolition of oscillations (APB, GABA, Glutamate, or DNQX), whereas other drugs merely reduced the oscillatory amplitudes (Bicuculline, Glycine, Strychnine, or HEPES) or did not even affect the oscillations (TPMPA). Assuming that rod bipolar cells (RBC) express metabotropic Glutamate receptors, GABAA, GABAC, and Glycine receptors and that they release glutamate mainly on Glycinergic AII amacrine cells and GABAergic A17 amacrine cells, which are differently affected by the mentioned drugs, we propose that RBC-AII/A17 reciprocal synapses are responsible for the OP generation in the ERG recordings in the mice. We conclude that the reciprocal synapses between RBC and AII/A17 are the basis of the ERG OP oscillations of the light response, and this fact must be taken into consideration in any ERG test that shows a decrease in the OPs' amplitude.

Pepperberg plot: Modeling flash response saturation in retinal rods of mouse.

Retinal rods evolved to be able to detect single photons. Despite their exquisite sensitivity, rods operate over many log units of light intensity. Several processes inside photoreceptor cells make this incredible light adaptation possible. Here, we added to our previously developed, fully space resolved biophysical model of rod phototransduction, some of the mechanisms that play significant roles in shaping the rod response under high illumination levels: the function of RGS9 in shutting off G protein transducin, and calcium dependences of the phosphorylation rates of activated rhodopsin, of the binding of cGMP to the light-regulated ion channel, and of two membrane guanylate cyclase activities. A well stirred version of this model captured the responses to bright, saturating flashes in WT and mutant mouse rods and was used to explain "Pepperberg plots," that graph the time during which the response is saturated against the natural logarithm of flash strength for bright flashes. At the lower end of the range, saturation time increases linearly with the natural logarithm of flash strength. The slope of the relation (τD) is dictated by the time constant of the rate-limiting (slowest) step in the shutoff of the phototransduction cascade, which is the hydrolysis of GTP by transducin. We characterized mathematically the X-intercept ( ) which is the number of photoisomerizations that just saturates the rod response. It has been observed that for flash strengths exceeding a few thousand photoisomerizations, the curves depart from linearity. Modeling showed that the "upward bend" for very bright flash intensities could be explained by the dynamics of RGS9 complex and further predicted that there would be a plateau at flash strengths giving rise to more than ~107 photoisomerizations due to activation of all available PDE. The model accurately described alterations in saturation behavior of mutant murine rods resulting from transgenic perturbations of the cascade targeting membrane guanylate cyclase activity, and expression levels of GRK, RGS9, and PDE. Experimental results from rods expressing a mutant light-regulated channel purported to lack calmodulin regulation deviated from model predictions, suggesting that there were other factors at play.

Light Adaptation of Rod Photoreceptor Synapses by a Transducin-Complexin-SNARE Complex Interaction

Light Adaptation of Rod Photoreceptor Synapses by a Transducin-Complexin-SNARE Complex Interaction

Electrophysiological Evaluation of Macular Photoreceptor Functions in Patients with Choroidal Neovascular Membranes

Purpose To evaluate changes in cone functions using light-adapted (LA) 30 Hz flicker and LA 3.0 electroretinography (ERG) in intravitreal ranibizumab (IVR)-treated naïve neovascular age-related macular degeneration (nAMD) patients. Materials and methods This retrospective interventional study reviewed the medical records of 32 nAMD patients (32 eyes) who received monthly IVR between January 2019 and January 2021. A comprehensive ophthalmic examination, including best-corrected visual acuity (BCVA) testing and slit-lamp biomicroscopy, was performed as part of their clinical care, followed by LA 30 Hz flicker and LA 3.0 ERGs, optical coherence tomography, and fundus fluorescein angiography. All measurements were taken before IVR (baseline), as well as at months 6 and 12 later. Treatment was resumed for up to 12 months if recurrence occurred. Results Compared to baseline, visual acuity improved significantly at months 6 and 12, respectively, coinciding with a significant decrease in central macular thickness (p < 0.05 for all). LA 30 Hz flicker ERG b-wave amplitude decreased significantly between baseline and months 6 and 12, respectively (p < 0.05 for both). There were no significant changes in LA 3.0 ERG a- and b-wave amplitudes between baseline and month 6 (p > 0.05 for both), but a significant decrease existed between baseline and month 12 (p < 0.05 for both). While LA 3.0 ERG a-wave implicit time increased significantly (p < 0.05 for both) between baseline and months 6 and 12, respectively, b-wave implicit time did not (p > 0.05 for both). Also, LA 30 Hz flicker ERG b-wave implicit times did not differ significantly between baseline and months 6 and 12, respectively (p > 0.05, for both). Conclusions IVR was associated with long-term electrophysiological changes in cone functions, as measured by LA 30 Hz flicker and LA 3.0 ERGs.

Evaluation of Design Method for Highway Adjacent Tunnel and Exit Connection Section Length Based on Entropy Method.

With the continuous construction of transportation infrastructure, intersection nodes have been increasing rapidly, bringing growing numbers of tunnel- and exit-adjacent sections (TEAS) in mountain expressways in China. With the complex variation in the surrounding environment, drivers always face congestion and confusion on tunnel and the exit connecting sections (TECS) without adequate length, meanwhile excessively long TECS create detours. To better provide a sustainable design strategy for TEAS, based on a certain section of expressway in Shaanxi, China, this paper establishes a theoretical calculation model through analysis. The characteristics of traffic flow and drivers' light adaptation at tunnel exit are obtained through data collection and driving tests, and the length requirements of the tunnel and exit connecting sections (TECS) are discussed. A VISSIM microscopic simulation model is also built under various design schemes and entropy-based multi-attribute decision making (EBMADM) is used to objectively calculate the weights of the four selected evaluation indexes. Then, the design schemes of the TECS with different lengths have been comprehensively evaluated. The results show the match between the evaluation results of EBMADM with theoretical calculations under existing traffic conditions, which proves the rationality of EBMADM in such problems. For more cases, the results of the EBMADM evaluation show a positive correlation between the length of TECS for the best performing design scheme with traffic volume and diverging ratio.

Broadband Visual Adaption and Image Recognition in a Monolithic Neuromorphic Machine Vision System

AbstractBio‐inspired machine visions have caused wide attentions due to the higher time/power efficiencies over the conventional architectures. Although bio‐mimic photo‐sensors and neuromorphic computing have been individually demonstrated, a complete monolithic vision system has rarely been studied. Here, a neuromorphic machine vision system (NMVS) integrating front‐end retinomorphic sensors and a back‐end convolutional neural network (CNN) based on a single ferroelectric‐semiconductor‐transistor (FST) device structure is reported. As a photo‐sensor, the FST shows a broadband (275–808 nm) retina‐like light adaption function with a large dynamic range of 20.3 stops, and as a unit of the CNN, the FST's weight can be linearly programmed. In total, the NMVS has a high recognition accuracy of 93.0% on a broadband‐dim‐image classification task, which is 20% higher than that of an incomplete system without the retinomorphic sensors. Because of the monolithic unit, the NVMS shows high feasibility for integrated bio‐inspired machine vision systems.

Analyzing the effect of light on lettuce Fv/Fm and growth by machine learning

Varied plant growth cultivations require different light conditions. To explore them with lettuce (Lactuca sativa L. cv. ‘Hong Kong glass’), five photosynthetic photon flux density (PPFD, 50, 150, 300, 450 and 600 μmol·m−2·s−1) levels were set in completely controlled circumstances. Using ordinary least squares (OLS), the appropriate PPFD was determined depending on the dark fluorescence characteristics. Following 14 h of treatment, a new PPFD of 200 μmol·m−2·s−1 was employed to monitor the adaptation process obtained using the genetic algorithm-support vector regression (GA-SVR) model. The results showed that Fv/Fm declined as PPFDs increased except for L50, and OLS with R2 and RMSE of 0.9710 and 0.0416 suggested 140.80 μmol·m−2·s−1 was the ideal PPFD. Little changed in the new PPFD adaptation procedure for, L50, L150, and L300. During 42 h of adaptation, the discretized curves of Fv/Fm using the GA-SVR model at various PPFDs revealed that Fv/Fm increasingly approached and eventually reached the same level. The quick change was in [290, 480] μmol·m−2·s−1 depending on the probability density distributions. The difference in change rates between the two PPFD treatments decreased, indicating that lettuce's light tolerance improved after the two phases. The largest sum Fv/Fm in L150 indicated a maintained growth state. Full-cycle cultivation revealed that 150 and 250 μmol·m−2·s−1 had the highest fresh biomass. In conclusion, in [290, 480] μmol·m−2·s−1, short-term high light could improve plant light adaptability in variable light. In the constant light of the plant factory with artificial lighting (PFAL), it was recommended to utilize the light intensity of 140.80 μmol·m−2·s−1, which can both maintain growth and save light energy. A more suitable solution might be chosen depending on the cultivation requirements.

The value of colour assessment in diagnostic dilemmas

AbstractBackground: When the goal of clinical assessment is to segment, divide, and classify cases into neat discrete boxes it can often be frustrating to encounter cases which do not fit standard diagnosis algorithms. However, such diagnostic dilemmas often provide a valuable insight into the boundaries of current clinical procedures and the potential value psychophysical assessment can provide when used in conjunction with standard diagnosis algorithms. We present such a case involving localized retinal dysfunction that is not fully consistent with signs of either autoimmune retinopathy or occult maculopathy.Methods: Specific visual function loss was investigated in a health 32‐year‐old male with suspected localized retinal dysfunction, affecting the central retina. Blood tests and electro‐diagnostics were carried out after the patient presented with acute onset ‘foggy’ central vision. The working diagnosis from this initial visit was autoimmune retinopathy and oral steroids were prescribed. Following no change in symptoms a year after initially presenting, the patient was referred to City, University of London for bespoke assessments of specific visual functions. These included assessments of central and peripheral red / green (RG) and yellow / blue (YB) colour vision, mesopic visual acuity (VA), functional contrast sensitivity (FCS), rod‐ and cone‐mediated flicker sensitivity, and pupil responses measured using both rod‐ and cone‐enhanced stimuli.Results: The loss of vision affected primarily the central 20° with a mean VA of 6/36 in each eye. Fundus images, fluorescein angiography, and full field electroretinograms (ERGs) were normal, but pattern and focal ERGs were undetectable indicating localized dysfunction in central vision with OCT images showing a disrupted ellipsoid zone in each eye. The patient's mean corpuscular volume was 69 femtoliters, with red cell indices suggestive of thalassemia. Testing at City, University of London confirmed a loss of VA and FCS in the central 10° field, although both VA and FCS depended strongly on light level and were less affected with negative contrast stimuli. A loss of RG and YB colour vision was also measured centrally. Outside the central 10° field EA had almost normal colour and spatial vision. Rod‐ and cone‐mediated, flicker thresholds were elevated, with cone thresholds 10‐fold higher than normal. Pre‐stimulus pupil size, constriction amplitudes and latencies were normal with both centrally presented and peripheral stimuli.Conclusions: Psychophysical measurements in a patient with presumed autoimmune maculopathy showed atypical macular dysfunction that appears to preferentially affect negative contrast stimuli. Despite damage to the retinal mechanisms involved in spatial vision and light adaptation pupil responses remained unaffected. This unusual case highlights the importance of detailed phenotyping in understanding unknown aetiology.

Gating and ion selectivity of Channelrhodopsins are critical for photo-activated orientation of Chlamydomonas as shown by in vivo point mutation

The green unicellular alga Chlamydomonas reinhardtii with two photoreceptors called channelrhodopsins is a model organism that gave birth to a new scientific field of biomedical studies, optogenetics. Although channelrhodopsins are helping to decipher the activity of the human brain, their functionality has never been extensively studied in the organism of origin, mainly due to the difficulties connected to reverse genetic interventions. In this study, we present a CRISPR-Cas9-based technique that enables a precise in vivo exchange of single amino acids in a selected gene. To shed light on the function of channelrhodopsins ChR1 (C1) and ChR2 (C2) in vivo, we deleted both channelrhodopsins independently in the wild-type strain and introduced point mutations in the remaining channel, causing modified photocycle kinetics and ion selectivity. The mutated strains, ΔC1C2-E123T, ΔC1C2-E90R and ΔC1C2-E90Q, showed about 100-fold decrease in photosensitivity, a reduced photophobic response and faster light adaptation rates due to accelerated photocycle kinetics and reduced Ca2+ conductance. Moreover, the ΔC1C2-E90Q with an additionally reduced H+ permeability produced an electrical response only in the presence of Na+ ions, highlighting a contribution and importance of H+ conductance to photocurrents in the wild-type algae. Finally, in the ΔC1C2-E90R strain with the channelrhodopsin selectivity converted to anions, no photo-responses were detected. We conclude that the precise photocycle kinetics and the particular ion selectivity of channelrhodopsins are the key parameters for efficient phototaxis in low light conditions.

Retinal Cyclic Nucleotide-Gated Channel Regulation by Calmodulin.

Retinal cyclic nucleotide-gated (CNG) ion channels bind to intracellular cGMP and mediate visual phototransduction in photoreceptor rod and cone cells. Retinal rod CNG channels form hetero-tetramers comprised of three CNGA1 and one CNGB1 protein subunits. Cone CNG channels are similar tetramers consisting of three CNGA3 and one CNGB3 subunits. Calmodulin (CaM) binds to two distinct sites (CaM1: residues 565-587 and CaM2: residues 1120-1147) within the cytosolic domains of rod CNGB1. The binding of Ca2+-bound CaM to CNGB1 promotes the Ca2+-induced desensitization of CNG channels in retinal rods that may be important for photoreceptor light adaptation. Mutations that affect Ca2+-dependent CNG channel function are responsible for inherited forms of blindness. In this review, we propose structural models of the rod CNG channel bound to CaM that suggest how CaM might cause channel desensitization and how dysregulation of the channel may lead to retinal disease.

A biophilic wellbeing framework for positive indoor-outdoor connections in energy-efficient Arctic buildings

This paper develops a biophilic wellbeing framework for positive indoor-outdoor connections in Arctic buildings to respond to occupants’ wellbeing and energy-efficiency requirements. Extreme cold weather and drastic photoperiods of Arctic climates could have adverse impacts on wellbeing and reduce connections with nature, i.e., identified as biophilia. Characteristics of positive relationships with extreme Arctic climatic stressors have not yet been comprehensively studied in terms of integrated wellbeing needs and energy efficiency requirements. This paper aims to articulate a fundamental wellbeing framework integrating thermal and photobiological needs with biophilic recommendations to characterize positive connections with Arctic climates for energy-efficient buildings. A scoping literature review is conducted to discuss occupants' thermal and photobiological needs in relation to biophilic recommendations and Arctic climatic conditions. As a case study, shortcomings of existing building practices in Cambridge Bay, Nunavut, Canada, are studied regarding wellbeing, indoor-outdoor connections, and energy-efficiency needs. The proposed wellbeing framework for positive indoor-outdoor connections in Arctic buildings integrates (i) thermal and (ii) photobiological indicators based on biophilic recommendations. The integrated wellbeing framework enables characterizing thermal and (photobiological) lighting adaptation scenarios responding to Arctic weather, daylighting, and photoperiods as well as energy efficiency. Intermediate spaces are also proposed as a prosing architectural solution to address the integrated wellbeing framework energy efficiency in arctic buildings. Overall, the proposed framework could help architects, building designers, and stakeholders to develop further architectural solutions for positive, energy-efficient indoor-outdoor connections for Arctic buildings and occupants.

Turbidity derived from palm oil mill effluent alters feeding ability of male siamese fighting fish (Betta splendens, Regan 1910)

To date, several harmful effects of Palm Oil Mill Effluent (POME) have been reported on aquatic organisms, including fish. However, the turbidity effects of POME on the feeding ability of fish are still unexplored. We first assessed the turbidity effects of POME on the feeding ability of male siamese fighting fish (Betta splendens). Siamese fighting fish were exposed to < 1 NTU (control) and five concentrations of POME turbidity levels, namely 20 NTU (Treatment A), 40 NTU (Treatment B), 60 NTU (Treatment C), 80 NTU (Treatment D), and 100 NTU (Treatment E). Each of the control and treatment groups was maintained in five replicates. Preference tests were carried out in a 10-L aquarium (35 ×21×25 cm3). The feeding rate, time to capture first prey, aggressive behaviour, foraging area, and retinal light adaptation rate and retina histopathology were analyzed. The exposure time for the determination of feeding rate, foraging area, and retinal light adaptation rate and retina histopathology was set for 15 min, while for aggressive behaviour test, the exposure duration was 5 min. Results showed that the feeding rate, aggressive behaviour and foraging area significantly decreased with increasing turbidity levels of POME. In contrast, the time to capture first prey significantly increased. No significant changes in retinal light adaptation rate was recorded between treatments. Furthermore, results showed several retinal degenerations, including reduced granular spherical cells (GL) and detachment of bipolar cells from photoreceptor cells (DBPC) in siamese fighting fish exposed to high-level turbidity of POME. This study provides valuable information to support POME remediation management, especially turbidity parameters.

Short‐Wave Infrared Synaptic Phototransistor with Ambient Light Adaptability for Flexible Artificial Night Visual System

AbstractFlexible organic monitoring system that can work in short‐wave infrared (SIR) region has great potential in autonomous driving, night driving safety, military encryption, biomedical imaging, and robot engineering. Especially, the development of infrared artificial vision system device that can autonomously improve the computing speed and adapt to different brightness ambient light is very important. However, it is a challenge for mimicking infrared visual adaptation because of the need for infrared absorbing materials and the need to control the concentration of carriers. In this study, inorganic quantum dot material is combined with organic materials to promote carrier separation and introduce interface defects that adjust the carrier concentration in transistors, which induce the synaptic behavior under SIR (1100 nm) light in darkness and the ability to adapt to white ambient light. Furthermore, the device array realizes the image recognition of SIR light at night with white ambient light of different brightness, exhibiting good self‐adaptability, and strong anti‐interference ability. These results demonstrate promising applications of the infrared synaptic phototransistors in adapted bionic optoelectronic devices.

HIV-1 CD4-binding site germline antibody–Env structures inform vaccine design

BG24, a VRC01-class broadly neutralizing antibody (bNAb) against HIV-1 Env with relatively few somatic hypermutations (SHMs), represents a promising target for vaccine strategies to elicit CD4-binding site (CD4bs) bNAbs. To understand how SHMs correlate with BG24 neutralization of HIV-1, we report 4.1 Å and 3.4 Å single-particle cryo-EM structures of two inferred germline (iGL) BG24 precursors complexed with engineered Env-based immunogens lacking CD4bs N-glycans. Structures reveal critical Env contacts by BG24iGL and identify antibody light chain structural features that impede Env recognition. In addition, biochemical data and cryo-EM structures of BG24iGL variants bound to Envs with CD4bs glycans present provide insights into N-glycan accommodation, including structural modes of light chain adaptations in the presence of the N276gp120 glycan. Together, these findings reveal Env regions critical for germline antibody recognition and potential sites to alter in immunogen design.

New prospectives on light adaptation of visual system research with the emerging knowledge on non-image-forming effect

Light adaptation is very important to keep the visual system acutely sensitive to scene content over a wide range of illumination, and has strong influence on brightness perception, visual performance and glare evaluation. The estimation method for the light adaptation state under real circumstances is a big pending topic for lighting industry. The discovery of Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs) has offered us an exciting entry point to comprehend how light adaptation is regulated. In this paper, we made a comprehensive and thorough analysis of forty-five studies focusing on light adaptation with the emerging knowledge on non-image-forming effect (NIF), to help researchers facilitate the research on light adaptation under complex luminance distribution. From the review, we can have the following outputs: 1) NIF may directly mediate the function of luminance adaptation, and we can take pupillary light reflex (PLR) as an objective indicator for the adaptation; 2) the action spectra of light adaptation may not be a fixed formula like V(λ), but may vary dynamically with luminance level; 3) there is high necessity to conduct research on light adaptation within a natural and complex environment. All these outputs can provide us a new perspective on light adaptation in visual system research.

Frmpd1 Facilitates Trafficking of G-Protein Transducin and Modulates Synaptic Function in Rod Photoreceptors of Mammalian Retina.

Trafficking of transducin (Gαt) in rod photoreceptors is critical for adaptive and modulatory responses of the retina to varying light intensities. In addition to fine-tuning phototransduction gain in rod outer segments (OSs), light-induced translocation of Gαt to the rod synapse enhances rod to rod bipolar synaptic transmission. Here, we show that the rod-specific loss of Frmpd1 (FERM and PDZ domain containing 1), in the retina of both female and male mice, results in delayed return of Gαt from the synapse back to outer segments in the dark, compromising the capacity of rods to recover from light adaptation. Frmpd1 directly interacts with Gpsm2 (G-protein signaling modulator 2), and the two proteins are required for appropriate sensitization of rod-rod bipolar signaling under saturating light conditions. These studies provide insight into how the trafficking and function of Gαt is modulated to optimize the photoresponse and synaptic transmission of rod photoreceptors in a light-dependent manner.

Application of fertilization in changing light adaptability and improving growth of Aralia elata (Miq.) Seem. seedlings under various light conditions in temperate forests

Non-timber forest plants have always played a significant role in livelihood security by providing valuable non-timber forest products, especially in less-developed countries. Artificial cultivation is a key approach to sustainably develop non-timber forest plants, for which, in-forest planting is vital. Light conditions in forests severely affect in-forest planting, and the growth of many plants may be restricted due to inappropriate light conditions. Thus, to fully and effectively utilize forest spaces with various light environments, fertilization, as an important practice to supply nutrients for promoting plant growth, was selected to mitigate light constraints in forests. Aralia elata (a valuable non-timber forest plant species) was chosen as the subject to explore the effects of fertilization on photosynthetic and morphological adaptation to light and the growth of in-forest planted seedlings by simulating different light environments. The results showed that the effects of fertilization on light adaptability (i.e., photosynthesis and leaf traits) of A. elata seedlings were limited; that is, only the variations in light-saturated photosynthetic net rate (PNmax), specific leaf area (SLA), and chlorophyll (Chl) content of A. elata seedlings between different shade intensities were noticeably affected by fertilization. Fertilization was positive for growth, and a half fertilization treatment (50 g per plot) was optimum for improving the growth of A. elata seedlings under light conditions of 0–75% shade intensities. These results can provide some practical references for the application of fertilization in in-forest planting and management of transplanted non-timber forest plant seedlings under various light conditions in the forests.

Monitoring the photosynthetic performance of grape leaves using a hyperspectral-based machine learning model

Photosynthesis is a direct expression of the crop growth status and an important indicator predicting yield and quality. Rapid and accurate monitoring of the dynamics of photosynthetic is key to field management. In this study, we obtained photosynthetic pigments and water status parameters at the leaf scale during different growth periods of grape. The potential maximum quantum yield (Fv/Fm) of photosystem II (PSII) under dark adaptation and the light response curve (LRC) of the PSII electron transfer rate (ETR) under light adaptation were measured using a pulse amplitude modulated (PAM) chlorophyll fluorometer, while leaf spectral information was recorded using a hyperspectral imager. The maximum ETR (ETRmax) and initial quantum efficiency (kα) were calculated using the LRC model. A Bayesian neural network (BNN) model (implemented in Tensorfolw2.8) was developed to predict Fv/Fm, ETRmax and kα by quantifying the spectral response indices of photosynthetic pigments and water status parameters. A comparison was made with the partial least squares (PLS) and photochemical reflectance index (PRI). The results show that BNN, PLS model and PRI have better predictive performance for Fv/Fm than ETRmax and kα. Compared with the PLS and PRI, the BNN model was able to significantly improve the prediction accuracy, where the validation results for Fv/Fm were R2 of 0.78, ETRmax of 0.57 and kα of 0.53. In addition, the importance of the BNN model input features varied with Fv/Fm, ETRmax and kα, with the vegetation index describing the photosynthetic pigments having the highest importance. The PRI had the worst predictive performance probably because the de-epoxidation state of the xanthophyll cycle pigments is strongly influenced by temporal changes. The model developed in this paper for monitoring photosynthetic performance parameters in grape leaves can simplify the complex photosynthetic reaction process, expand the application of PAM technology and provide a method for rapid and accurate monitoring of photosynthetic performance.

The Impact of Cameraria ohridella (Lepidoptera, Gracillariidae) on the State of Aesculus hippocastanum Photosynthetic Apparatus in the Urban Environment

The paper presents the results on resistance of Aesculus hippocastanum Linnaeus, 1753 trees to Cameraria ohridella Deschka &amp; Dimić, 1986 (Lepidoptera, Gracillariidae) impact under conditions of a modern urban environment on the example of Dnipro city as the largest industrial city in Ukraine. Field experiments were conducted in all park areas of the city, which allowed covering the full gradient of the existing urban environment and considered the different degrees of the tree settlement by the invasive insect species. The research of the impact of C. ohridella caterpillars’ vital activity on the photosynthetic apparatus state was carried out by applying a chlorophyll fluorescence induction technique. Diagnosis of photosynthetic dysfunction of fresh Ae. hippocastanum leaves was conducted using a portable “Floratest” fluorometer manufactured in Ukraine. Interpretation of the obtained Kautsky curves showed that significant changes in their critical parameters associated with the degree of leaf damage by C. ohridella caterpillars were not detected. The influence of tree growth site conditions on the following 4 main indicators of chlorophyll fluorescence induction was established: the initial value of fluorescence induction after irradiation; the value of “plateau” fluorescence induction; the maximum value of fluorescence induction; the stationary value of fluorescence induction after light adaptation of the plant leaf. It was found that the efficiency coefficients of photochemical processes in Ae. hippocastanum trees growing in low terrain levels differed significantly, which can probably be interpreted as their response to the specific characteristics of the urban environment.