Light Saturation Research Articles

Attenuation of photosynthesis in nanosilver-treated Arabidopsis thaliana is inherently linked to the particulate nature of silver

Silver nanoparticles (AgNPs) are known to affect the physiology and morphology of plants in various ways, but the exact mechanism by which they interact with plant cells remains to be elucidated. An unresolved question of silver nanotoxicology is whether the interaction is triggered by the physical features of the particles, or by silver ions leached from their surface. In this study, we germinated and grew Arabidopsis thaliana seedlings in synthetic medium supplemented with sub-morbid concentrations (4 μg/mL) of AgNPs and silver nitrate (AgNO3). This treatment led to in planta accumulation of 106 μg/g and 97 μg/g of silver in the AgNO3- and AgNP-exposed seedlings, respectively. Despite the statistically indistinguishable silver accumulation, RNA sequencing data demonstrated distinct changes in the transcriptome of the AgNP-exposed, but not in the AgNO3-exposed plants. AgNP exposure induced changes in the expression of genes involved in immune response, cell wall organization, photosynthesis and cellular defense against reactive oxygen species. AgNO3 exposure, on the other hand, caused the differential expression of only two genes, neither of which belonged to any AgNP-enriched gene ontology categories. Moreover, AgNP exposure led to a 39% reduction (p < 0.001) in total chlorophyll concentration relative to untreated plants which was associated with a 56.9% and 56.2% drop (p < 0.05) in carbon assimilation rate at ambient and saturating light, respectively. Stomatal conductance was not significantly affected by AgNP exposure, and limitations to carbon assimilation, as determined through analysis of light and carbon dioxide (A/Ci) curves, were attributed to rates of electron transport, maximum carboxylation rates and triose phosphate use. AgNO3-exposure, on the other hand, did not lead to significant reduction either in chlorophyll concentration or in carbon assimilation rate. Given these data, we propose that the impact of AgNPs cannot be simply attributed to the presence of the metal in plants, but is innate to the particulate nature of nanosilver.

Yield and Photosynthesis Related to Growth Forms of Two Strawberry Cultivars in a Plant Factory with Artificial Lighting

Appropriate growth forms for strawberry production in a plant factory with artificial lighting (PFAL), which is a recently developed production system, remain undetermined. Improving strawberry productivity in a PFAL requires insights into the interplay between production characteristics (growth and photosynthesis) and growth forms, such as plant height and leaf area (LA), which are major determinants of crop yield. Growth status, yield, and photosynthetic characteristics of the two cultivars of strawberries (Fragaria ×ananassa Duch. Tochiotome and Koiminori) with different growth forms were examined. ‘Koiminori’ exhibited a 1.9-fold higher yield and a 2.0-fold greater total dry weight of respective organs compared with ‘Tochiotome’. The single-plant photosynthetic rate (AP), serving as an index for both cultivars, was 2.2-times higher for Koiminori than for Tochiotome. The photosynthetic rates of a single leaf (AL) and LA were also analyzed as important factors that influence the AP. The AL for ‘Koiminori’ surpassed that of ‘Tochiotome’ by 1.4 times. This was attributed to the elevated photosynthetic photon flux density received by the upper leaves of Koiminori, which is a consequence of its higher plant height in proximity to the light source. Evaluation of four photosynthetic capacities, maximum rate of carboxylation, maximum rate of electron transport, photosynthetic rate under saturating light, and light utilization efficiency, which are potential factors that affect AL, revealed no differences in these capacities between cultivars. ‘Koiminori’ exhibited a significantly larger LA (2.3- to 3.1-times) than ‘Tochiotome’, indicating that the former’s higher AP resulted mainly from its higher AL and larger LA. Thus, strawberry production in a PFAL can be improved by growing cultivars with growth forms such as higher plant height and larger LA.

Photosynthetic response of Chara braunii towards different bicarbonate concentrations.

A variety of inorganic carbon acquisition modes have been proposed in Characean algae, however, a broadly applicable inorganic carbon uptake mechanism is unknown for the genus Chara. In the present study, we analyzed if C. braunii can efficiently use HCO3 - as a carbon source for photosynthesis. For this purpose, C. braunii was exposed to different concentrations of NaHCO3 - at different time scales. The photosynthetic electron transport through photosystem I (PSI) and II (PSII), the maximum electron transport rate (ETRmax ), the efficiency of the electron transport rate (α, the initial slope of the ETR), and the light saturation point of photosynthesis (Ek ) were evaluated. Additionally, pigment contents (chlorophyll a, chlorophyll b, and carotenoids) were determined. Bicarbonate addition positively affected ETRmax , after direct HCO3 - application, of both PSII and PSI, but this effect seems to decrease after 1 h and 24 h. Similar trends were seen for Ek , but no significant effect was observed for α. Pigment contents showed no significant changes in relation to different HCO3 - concentrations. To evaluate if cyclic electron flow around PSI was involved in active HCO3 - uptake, the ratio of PSI ETRmax /PSII ETRmax was calculated but did not show a distinctive trend. These results suggest that C. braunii can utilize NaHCO3 - in short-term periods as a carbon source but could rely on other carbon acquisition mechanisms over prolonged time periods. These observations suggest that the minor role of HCO3 - as a carbon source for photosynthesis in this alga might differentiate C. braunii from other examined Chara spp.

Effects of summer pruning on the growth and photosynthetic characteristics of pepper (Capsicum annuum L.)

The objective of the study is to investigate the mechanism by which summer pruning enhances the growth of pepper plants, as indicated by growth and fruit appearance indicators, photosynthetic rate and gas exchange parameters, rapid light response and induction kinetics curves and the related chlorophyll fluorescence parameters. The results indicated that the leaf growth rate, the individual pepper fruit weight, and the fruit longitudinal and cross diameters of the pruned group were significantly higher than those of the control. The stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr) of the pruned group were significantly higher than those of the control. The initial slope of the rapid light response curve, which represents light energy utilisation efficiency (α), the maximum electron transfer rate (Jmax) and saturated light intensity (PARsat) were all higher in the summer pruning group than in the control group. The F0 of the pruned group decreased by 16.83%, Fv/F0 increased by 23.69%, PIabs increased by 58.33%, and DIo/RC decreased by 22.09% compared to the control group. In summary, summer pruning significantly improves the leaf growth rate and fruit appearance quality of pepper, effectively promotes the photosynthesis of functional leaves, and reduces the degree of stress under adverse environmental conditions.

Physiological efficiency of grapevine canopies having varying geometries: Seasonal and diurnal whole canopy gas exchange assessment under well-watered and water deficit conditions

Grapevine training systems should be thoroughly examined to contribute to vineyards more resilient to climate change. This study was conducted on 18 three-year-old fruiting Sangiovese vines grown in pots outdoors with canopies trained to a vertical shoot positioned (VSP) spur-pruned cordon, a single high wire (SHW), and a Pergola (P) training system. Whole-canopy net CO2 exchange rate (NCER) and transpiration (T) were monitored by an enclosure system on a 24/7 basis from DOY 179–249. All vines were kept well-watered (WW) from DOY 179 to DOY 199, and the water supply was first reduced to 50% (DOY200–204) and then to 35% (DOY 205–214) before final rewatering (DOY 215–217). Vegetative growth, yield components, and grape composition were also assessed. Seasonal gas exchange on a per vine basis reflected vine size given as total leaf area (LA) varying from 2.5 to 3.1 m2; however, when diurnal trends of NCER/LA and T/LA within the WW and rewatering periods were considered, the good correlations found with the modeled total canopy light interception (TCLI) in SHW and P, were not confirmed in VSP. In all canopy geometries, the best predictor of NCER/LA was the total direct light intensity, whereas T/LA was linearly and closely correlated with air VPD. In terms of NCER/LA during the WW period, SHW had 24% higher rates than VSP and P. Under progressive water stress, SHW again exhibited higher drought resilience, while NCER and T were severely reduced in VSP and P. Severe stress also caused lower light saturation points and quantum yield in VSP and P. Under similar yield levels, P reached the best fruit maturity. In terms of photosynthetic efficiency and adaptive response to increasing water stress, the SHW performed best. Results extrapolated at the field level indicate the P system as the most rewarding.

Addressing the long-standing limitations of double exponential and non-rectangular hyperbolic models in quantifying light-response of electron transport rates in different photosynthetic organisms under various conditions.

The models used to describe the light response of electron transport rate in photosynthesis play a crucial role in determining two key parameters i.e., the maximum electron transport rate (J max) and the saturation light intensity (I sat). However, not all models accurately fit J-I curves, and determine the values of J max and I sat. Here, three models, namely the double exponential (DE) model, the non-rectangular hyperbolic (NRH) model, and a mechanistic model developed by one of the coauthors (Z-P Ye) and his coworkers (referred to as the mechanistic model), were compared in terms of their ability to fit J-I curves and estimate J max and I sat. Here, we apply these three models to a series of previously collected Chl a fluorescence data from seven photosynthetic organisms, grown under different conditions. Our results show that the mechanistic model performed well in describing the J-I curves, regardless of whether photoinhibition/dynamic down-regulation of photosystem II (PSII) occurs. Moreover, both J max and I sat estimated by this model are in very good agreement with the measured data. On the contrary, although the DE model simulates quite well the J-I curve for the species studied, it significantly overestimates both the J max of Amaranthus hypochondriacus and the I sat of Microcystis aeruginosa grown under NH4 +-N supply. More importantly, the light intensity required to achieve the potential maximum of J (J s) estimated by this model exceeds the unexpected high value of 105 μmol photons m-2 s-1 for Triticum aestivum and A. hypochondriacus. The NRH model fails to characterize the J-I curves with dynamic down-regulation/photoinhibition for Abies alba, Oryza sativa and M. aeruginosa. In addition, this model also significantly overestimates the values of J max for T. aestivum at 21% O2 and A. hypochondriacus grown under normal condition, and significantly underestimates the values of J max for M. aeruginosa grown under NO3 -N supply. Our study provides evidence that the 'mechanistic model' is much more suitable than both the DE and NRH models in fitting the J-I curves and in estimating the photosynthetic parameters. This is a powerful tool for studying light harvesting properties and the dynamic down-regulation of PSII/photoinhibition.

Identification of Olives Using In-Field Hyperspectral Imaging with Lightweight Models.

During the growing season, olives progress through nine different phenological stages, starting with bud development and ending with senescence. During their lifespan, olives undergo changes in their external color and chemical properties. To tackle these properties, we used hyperspectral imaging during the growing season of the olives. The objective of this study was to develop a lightweight model capable of identifying olives in the hyperspectral images using their spectral information. To achieve this goal, we utilized the hyperspectral imaging of olives while they were still on the tree and conducted this process throughout the entire growing season directly in the field without artificial light sources. The images were taken on-site every week from 9:00 to 11:00 a.m. UTC to avoid light saturation and glitters. The data were analyzed using training and testing classifiers, including Decision Tree, Logistic Regression, Random Forest, and Support Vector Machine on labeled datasets. The Logistic Regression model showed the best balance between classification success rate, size, and inference time, achieving a 98% F1-score with less than 1 KB in parameters. A reduction in size was achieved by analyzing the wavelengths that were critical in the decision making, reducing the dimensionality of the hypercube. So, with this novel model, olives in a hyperspectral image can be identified during the season, providing data to enhance a farmer's decision-making process through further automatic applications.

Natural Albino Mutant of Daylily (Hemerocallis spp.) Reveals a Link between Drought Sensitivity and Photosynthetic Pigments Metabolism.

Mutant analysis remains one of the main genetic tools for characterising unclarified gene functions in plants, especially in non-model plants. Daylily (Hemerocallis spp.) is a popular perennial ornamental plant grown worldwide. Analysis of daylily mutants can enhance understanding of genes regulating the albino phenotype and improve the cultivar quality of daylily. The natural albino mutant (Alb-⁣/-) was isolated by screening a self-pollinated progeny of daylily cultivar 'black-eyed stella'. Transmission electron microscopy was used in analysing the structure of plastids between mutant and wild-type seedlings. The content of chlorophyll, carotenoids and chlorophyll precursors in plants was measured by ultraviolet spectrophotometry. RNA sequencing and physiological measurements were performed to explore the association between drought tolerance and mutation. All the seedlings of the daylily albino mutants died spontaneously within fifteen days after germination when grown in soil. The carotenoid and chlorophyll content in the leaves of the mutant plants significantly decreased compared with those of the wild-type control. The mutant plants displayed stunted growth, and their leaves were white or light yellow in color. Abnormal plastids such as those showing endomembrane vesiculation and lacking stacking were discovered in the leaves of mutant plants. Furthermore, genetic analysis revealed that a single recessive nuclear gene mutation led to the albino trait, RNA sequencing and real-time quantitative PCR validation showed extensive differences in gene expression between the mutant plants and the wild-type control, and most of the genes related to chlorophyll metabolism were down-regulated, with foldchange ranging from 0.20-0.49. Additionally, the surviving homozygous plants (Alb+⁣/+), which do not contain this mutation, were also isolated by analysing the phenotype of their self-pollinated progeny. The net photosynthesis rate and light saturation point of Alb+⁣/+ were higher than those of heterozygous (Alb+⁣/-) plants. Additionally, the Alb+⁣/+ plants were more tolerant to drought conditions than the Alb+⁣/- plants, suggesting that a heterozygous Alb- mutation is sufficient to negatively affect photosynthetic efficiency and drought tolerance. The albino mutation negatively affects photosynthetic efficiency and drought tolerance, and homozygous mutation is required for the characteristic albino phenotype. This work highlights the link between albino mutation, photosynthetic pigment metabolism and drought sensitivity in daylily.

Red quantum-dot common layer for organic-quantum-dot hybrid light-emitting diodes for full-color displays

Organic and quantum dot (QD) light-emitting diodes (OLEDs and QLEDs, respectively) have been known for their practical application in full-color displays. Each primary color-emitting layer (EML) needs to be patterned via fine metal shadow masks (FMMs) or inkjet printing. However, the FMM method suffers from a shadow effect, misalignment, and size limitation, while inkjet printing hinders fine patterning, which disrupts high-resolution, large-scale fabrication. Here, we show a novel organic–QD hybrid device architecture by introducing a red QD common layer (QDCL). Since the QDCL is deposited onto all sub-pixels in a solution process without patterning, one patterning step for the red sub-pixel is reduced for full-color display fabrication. The green and blue OLEDs incorporating a red-emitting QDCL emitted their own color, owing to the effective exciton confinement within the EML by adopting a buffer layer, while the QDs in the QDCL emitted saturated red light. As a result, we could demonstrate a full-color organic–QD hybrid light-emitting device fabricated on a single substrate using the QDCL. We believe our strategy would help fabricate full-color and high-resolution displays with reduced manufacturing costs and time.

Microstructure, optical, and electrical characteristics of NaBaBi2(PO4)3: Sm3+ orange-red phosphor for WLEDs

White light-emitting diodes (WLEDs) are widely used as lighting devices in daily life. However, due to the scarcity of orange-red components, they lack warm white light. Therefore, there is an urgent need for orange-red phosphors to improve the lighting quality and generate more saturated and warm white light. In this regard, NaBaBi2(PO4)3: xSm3+ orange-red phosphors were synthesized using the solid-state method. A systematic study was conducted on the microstructure, optical, and electrical properties of NaBaBi2(PO4)3: xSm3+ phosphors through various characterizations such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, fluorescence decay curves, and electrochemical impedance spectroscopy. The diffuse reflectance spectrum indicates that with the increase of Sm3+ doping concentration, the optical bandgap decreases. Remarkably, the NaBaBi2(PO4)3: 0.05Sm3+ phosphor has good thermal stability, and its retention rate is 84.42% at a high temperature of 428 K. Furthermore, the packaged LED manifested desirable characteristics, such as a low correlated color temperature (CCT ∼ 4280 K) and a high color rendering index (CRI ∼ 82), as evidenced by rigorous testing. These results indicate that the NaBaBi2(PO4)3: Sm3+ phosphors have a significant potential for utilization in the LED lighting industry.

Lake-wide measurements of primary productivity in Lake Erie

Abstract Few lake-wide, seasonal primary production measurements have been made in Lake Erie. None more recent than 1997 have been reported in the literature. In 2019 we used 13C uptake to measure production at 11 stations across the lake during three surveys in May, July, and September and at four of these stations during two additional surveys in April and August. Samples were collected at two depths (2 m and 6 m) and incubated on deck using eight levels of irradiance. We fit the resultant photosynthesis-irradiance curves with models that included the initial slope at low light levels, the maximum photosynthesis rate at light saturation, and when warranted, the negative slope at high irradiance. During May, there was little variation in chlorophyll-normalized volumetric productivity with sample depth, and productivity generally was higher nearshore and in the western basin than it was offshore. The distinction between nearshore and offshore stations was less pronounced in July, but nearshore productivity was higher than offshore in September. Using the photosynthesis data from all five surveys, chlorophyll concentration profiles, and estimated clear-sky solar insolation, we calculated time series of vertically integrated daily production at a western basin station, two central basin stations, and an eastern basin station. Central basin production was highest during August, estimated to be 748 mg C m-2 d-1 and 779 mg C m-2 d-1 at our two stations. Production peaked in July in the western basin (510 mg C m-2 d-1) and September in the eastern basin (421 mg C m-2 d-1). Whole-lake seasonal areal phytoplankton photosynthesis was estimated as 1.661E6 tonnes, about half of estimates made in the 1990s using 14C methods. These results inform our understanding of spatial-temporal trends in Lake Erie productivity and highlight the need for continued measurements of Lake Erie primary production.

Enhanced drought tolerance and photosynthetic efficiency in Arabidopsis by overexpressing phosphoenolpyruvate carboxylase from a single-cell C4 halophyte Suaeda aralocaspica.

In crop genetic improvement, the introduction of C4 plants' characteristics, known for high photosynthetic efficiency and water utilization, into C3 plants has been a significant challenge. This study investigates the effects of the desert halophyte Suaeda aralocaspica SaPEPC1 gene from a single-cell C4 photosythetic pathway, on drought resistance and photosynthetic performance in Arabidopsis. We used transgenic Arabidopsis with Zea mays ZmPEPC1 from C4 plant with classic Kranz anatomical structure and Arabidopsis AtPEPC1 from C3 photosynthetic cycle plants as controls. The results demonstrated that C4 photosynthetic-type PEPCs could improve drought resistance in plants through stomatal closure, promoting antioxidant enzyme accumulation, and reducing reactive oxygen species (ROS) accumulation. Overexpression of SaPEPC1 was significantly more effective than ZmPEPC1 in enhancing drought tolerance. Notably, overexpressed SaPEPC1 significantly improved light saturation intensity, electron transport rate (ETR), photosynthetic rate (Pn), and photoprotection ability under intense light. Furthermore, overexpression SaPEPC1 or ZmPEPC1 enhanced the activity of key C4 photosynthetic enzymes, including phosphoenolpyruvate carboxylase (PEPC), pyruvate orthophosphate dikinase (PPDK) and NADP-malic enzyme (NADP-ME), and promoted photosynthetic product sugar accumulation. However, with AtPEPC1 overexpression showing no obvious improvement effect on drought and photosynthetic performance. Therefore, these results indicated that introducing C4-type PEPC into C3 plants can significantly enhance drought resistance and photosynthetic performance. However, SaPEPC1 from a single-cell C4 cycle plant exhibits more significant effect in ETR and PSII photosynthesis performance than ZmPEPC1 from a classical C4 anatomical structure plant, although the underlying mechanism requires further exploration.

Cell size differences affect photosynthetic capacity in a Mesoamerican and an Andean genotype of Phaseolus vulgaris L.

The efficiency of CO2 flux in the leaf is hindered by a several structural and biochemical barriers which affect the overall net photosynthesis. However, the dearth of information about the genetic control of these features is limiting our ability for genetic manipulation. We performed a comparative analysis between three-week-old plants of a Mesoamerican and an Andean cultivar of Phaseolus vulgaris at variable light and CO2 levels. The Mesoamerican bean had higher photosynthetic rate, maximum rate of rubisco carboxylase activity and maximum rate of photosynthetic electron transport at light saturation conditions than its Andean counterpart. Leaf anatomy comparison between genotypes showed that the Mesoamerican bean had smaller cell sizes than the Andean bean. Smaller epidermal cells in the Mesoamerican bean resulted in higher stomata density and consequently higher stomatal conductance for water vapor and CO2 than in the Andean bean. Likewise, smaller palisade and spongy mesophyll cells in the Mesoamerican than in the Andean bean increased the cell surface area per unit of volume and consequently increased mesophyll conductance. Finally, smaller cells in the Mesoamerican also increased chlorophyll and protein content per unit of leaf area. In summary, we show that different cell sizes controls the overall net photosynthesis and could be used as a target for genetic manipulation to improve photosynthesis.

Non-photochemical quenching may contribute to the dominance of the pale mat-forming lichen Cladonia stellaris over the sympatric melanic Cetraria islandica.

The mat-forming fruticose lichens Cladonia stellaris and Cetraria islandica frequently co-occur on soils in sun-exposed boreal, subarctic, and alpine ecosystems. While the dominant reindeer lichen Cladonia lacks a cortex but produces the light-reflecting pale pigment usnic acid on its surface, the common but patchier Cetraria has a firm cortex sealed by the light-absorbing pigment melanin. By measuring reflectance spectra, high-light tolerance, photosynthetic responses, and chlorophyll fluorescence in sympatric populations of these lichens differing in fungal pigments, we aimed to study how they cope with high light while hydrated. Specimens of the two species tolerated high light equally well but with different protective mechanisms. The mycobiont of the melanic species efficiently absorbed excess light, consistent with a lower need for its photobiont to protect itself by non-photochemical quenching (NPQ). By contrast, usnic acid screened light at 450-700nm by reflectance and absorbed shorter wavelengths. The ecorticate usnic species with less efficient fungal light screening exhibited a consistently lower light compensation point and higher CO2 uptake rates than the melanic lichen. In both species, steady state NPQ rapidly increased at increasing light with no signs of light saturation. To compensate for less internal shading causing light fluctuations with a larger amplitude, the usnic lichen photobiont adjusted to changing light by faster induction and faster relaxation of NPQ rapidly transforming excess excitation energy to less damaging heat. The high and flexible NPQ tracking fluctuations in solar radiation probably contributes to the strong dominance of the usnic mat-forming Cladonia in open lichen-dominated heaths.

Metabolomic Analysis of the Effect of Freezing on Leaves of Malus sieversii (Ledeb.) M.Roem. Histoculture Seedlings.

Malus sieversii (Ledeb.) M.Roem. is the ancestor of cultivated apples, and is an excellent germplasm resource with high resistance to cold. Artificial refrigerators were used to simulate the low temperature of -3 °C to treat Malus sieversii (Ledeb.) M.Roem. histoculture seedlings. Observations were performed to find the effects of freezing stress on the status of open or closed stomata, photosystems, and detection of metabolomic products in leaves of Malus sieversii (Ledeb.) M.Roem. histoculture seedlings. The percentage of closed stomata in the Malus sieversii (Ledeb.) M.Roem. histoculture seedlings increased, the maximum fluorescence (Fm') excited by a strong light (saturating pulse) was weakened relative to the real-time fluorescence in its vicinity, and the quantum yield of unregulated energy dissipation was increased in PSII under freezing stress. The metabolites in the leaves of the Malus sieversii (Ledeb. M.Roem.) histoculture seedlings were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry using CK, T12h, T36 h, and HF24h. Results demonstrated that cold stress in the Malus sieversii (Ledeb.) M.Roem. histoculture seedlings led to wilting, leaf stomatal closure, and photosystem damage. There were 1020 metabolites identified as lipids (10.2%), nucleotides and their derivatives (5.2%), phenolic acids (19.12%), flavonoids (24.51%), amino acids and their derivatives (7.75%), alkaloids (5.39%), terpenoids (8.24%), lignans (3.04%), organic acids (5.88%), and tannins (0.88%). There were 110 differential metabolites at CKvsT12h, 113 differential metabolites at CKvsT36h, 87 differential metabolites at T12hvsT36h, 128 differential metabolites at CKvsHF24h, 121 differential metabolites at T12hvsHF24h, and 152 differential metabolites at T36hvsHF24h. The differential metabolites in the leaves of the Malus sieversii (Ledeb.) M.Roem. seedlings grown under low-temperature stress mainly involved glycolysis, amino acid metabolism, lipid metabolism, pyrimidine metabolism, purine metabolism, and secondary metabolite metabolism. The Malus sieversii (Ledeb.) M.Roem. seedlings responded to the freezing stress by coordinating with each other through these metabolic pathways. The metabolic network of the leaves of the Malus sieversii (Ledeb.) M.Roem. histoculture seedlings under low temperature stress was also proposed based on the above pathways to deepen understanding of the response of metabolites of Malus sieversii (Ledeb.) M.Roem. to low-temperature stress and to lay a theoretical foundation for the development and utilization of Malus sieversii (Ledeb.) M.Roem. cultivation resources.

Integrative Physiological, Transcriptome, and Proteome Analyses Provide Insights into the Photosynthetic Changes in Maize in a Maize-Peanut Intercropping System.

Intercropping is a traditional and sustainable planting method that can make rational use of natural resources such as light, temperature, fertilizer, water, and CO2. Due to its efficient resource utilization, intercropping, in particular, maize and legume intercropping, is widespread around the world. However, the molecular details of these pathways remain largely unknown. In this study, physiological, transcriptome, and proteome analyses were compared between maize monocropping and maize-peanut intercropping. The results show that an intercropping system enhanced the ability of carbon fixation and carboxylation of maize leaves. Apparent quantum yield (AQY), the light-saturated net photosynthetic rate (LSPn), the light saturation point (LSP), and the light compensation point (LCP) were increased by 11.6%, 9.4%, 8.9%, and 32.1% in the intercropping system, respectively; carboxylation efficiency (CE), the CO2 saturation point (Cisat), the Rubisco maximum carboxylation rate (Vcmax), the maximum electron transfer rate (Jmax), and the triose phosphate utilization rate (TPU) were increased by 28.5%, 7.3%, 18.7%, 29.2%, and 17.0%, respectively; meanwhile, the CO2 compensation point (Γ) decreased by 22.6%. Moreover, the transcriptome analysis confirmed the presence of 588 differentially expressed genes (DEGs), and the numbers of up-regulated and down-regulated genes were 383 and 205, respectively. The DEGs were primarily concerned with ribosomes, plant hormone signal transduction, and photosynthesis. Furthermore, 549 differentially expressed proteins (DEPs) were identified in the maize leaves in both the maize monocropping and maize-peanut intercropping systems. Bioinformatics analysis revealed that 186 DEPs were related to 37 specific KEGG pathways in each of the two treatment groups. Based on the physiological, transcriptome, and proteome analyses, it was demonstrated that the photosynthetic characteristics in maize leaves can be improved by maize-peanut intercropping. This may be related to PS I, PS II, cytochrome b6f complex, ATP synthase, and photosynthetic CO2 fixation, which is caused by the improved CO2 carboxylation efficiency. Our results provide a more in-depth understanding of the high yield and high-efficiency mechanism in maize and peanut intercropping.

Artificial neural networks prediction and optimization based on four light regions for light utilization from Synechocystis sp. PCC 6803

Light is crucial in microalgae growth. However, dividing the microalgae growth region into light and dark regions has limitations. In this study, the light response of Synechocystis sp. PCC 6803 was investigated to define four light regions (FLRs): light compensation region, light limitation region, light saturation region, and photoinhibition region. The proportions of cells’ residence time in the FLRs and the number of times cells (NTC) passed through the FLRs in photobioreactors were calculated by using MATLAB. Based on the FLRs and NTC passed through the FLRs, a growth model was established by using artificial neural network (ANN).The ANN model had a validation R2 value of 0.97, which was 76.36% higher than the model based on light-dark regions. The high accuracy of the ANN model was further verified through dynamic adjustment of light intensity experiments.This study confirmed the importance of the FLRs for studying microalgae growth dynamics.

Daylight Quality Assessment of Rooms with Lateral Daylighting by the Room Light Saturation Criterion

The availability of daylight for residential and public spaces is extremely important. However, not always enough light to solve visual problems ensures the quality of the light environment in the room. The development of recommendations for improving the quality of daylighting is an important and urgent task, since the quality of human life and work depends on it, as well as energy savings. A criterion of light saturation of a room has been introduced into the norms, the evaluation characteristic of which is cylindrical illuminance only for electrical lighting. The article presents the results of a fullscale psychophysical experiment to assess the qualitative indicator of natural illumination of rooms with side light openings. The analysis of subjective assessments of observers showed the absence of a relationship between high estimates of the saturation of the room with light and the values of the relative horizontal illuminance of the daylight factor Dh, as well as the relative cylindrical illuminance of the Dc. However, there is a correlation between the feeling of comfort of the light environment and the values of the Dc/Dh ratio. The proposals on the normalized value and its values corresponding to the levels of saturation with daylight of the room are formulated. The analysis of the data obtained from the results of the experiment allowed us to establish that the quality of lighting of the workplace and the room as a whole is highly appreciated by the observer in terms of saturation level if the ratio of Dc/Dh in the centre of the room is located in the interval 1–1.3, while the value of the cylindrical illuminance Ec at the point furthest from the light transmission with a high assessment of light saturation by observers is Ec = 120 lx, Dc = 2 %.

Agrivoltaics: A Sustainable Method Of Farming For Various Suitable Crops

Agrivoltaics usage in the farmer fields is a new way to get profitable income as this system allows crops cultivation and electricity generation simultaneously on the same piece of land at the same time. This system enables the farmers to gain several benefits such as optimized land use, productivity improvement in the energy and water sector, economic benefits, etc. India receives ample supply of energy from the sun, but it is not yet utilized efficiently. In an agrivoltaic system, the output of crops will be affected by shade which is provided by panels as they allow very little solar radiation passage for fixation of CO2 by crop. Solar radiation, PAR, and Light Saturation Point are vital indices to enhance plant biomass. Generally shade-loving or tolerant crops are preferable under agrivoltaics. However, shade-intolerant crops can also be grown in interspaces where crops can capture a sufficient amount (&gt; 50%) of sun-light. The shade provided by APV creates a microclimate suitable for practicing cultivation in arid regions, livestock (rangevoltaics) and aquaponics etc. Some of the crops like cherry, bell pepper, lettuce, grapes, berries, and other cool season crop plants etc. showed better response under APV and reported enhanced growth, yield, and quality compared to conventional farming. The electricity generated by PV would improve the farmer’s socio-economic status, and land productivity and helps to curtail environmental pollution.

Ecological and Physiological Characteristics and Biotechnological Potential of Diatom Algae Nitzschia amabilis H. Suzuki

The study is focused on the ecological and physiological properties, production, and biochemical characteristics of the diatom Nitzschia amabilis. The optimum salinity (35‒36‰), illumination (2.95 klx), and photoperiod (14 h) at which the highest specific cell growth rate is achieved was determined. The coefficient of light saturation (Ik) was calculated and turned out to be lower than one, which indicates the high energy efficiency of photosynthesis. The results of experiments on salinity showed the ability of the alga to grow in the range of 4–68‰, indicating its relatively broad euryhalinity. The biochemical composition of N. amabilis during acumulative cultivation was studied. In general, polyunsaturated fatty acids predominated in the studied strain; eicosapentaenoic, arachidonic, and docosahexaenoic acids were dominant. The main share of saturated fatty acids consisted of palmitic acid. The productivity indicators of N. amabilis in relation to lipids, fucoxanthin, and PUFAs, which were 2.5–3 times higher in the flow cultivation mode than in the cumulative mode, have been established.