A High-Throughput Approach for Photosynthesis Studies in a Brassicaceae Panel.

The study of natural variations in photosynthesis in the Brassicaceae family offers the possibility of identifying mechanisms to enhance photosynthetic efficiency in crop plants. Indeed, this family, and particularly its tribe Brassiceae, has been shown to harbor species that have a higher-than-expected photosynthetic efficiency, possibly as a result of a complex evolutionary history. Over the past two decades, methods have been developed to measure photosynthetic efficiency based on chlorophyll fluorescence. Chlorophyll fluorescence measurements are performed with special cameras, such as the FluorCams, which can be included in robotic systems to create high-throughput phenotyping platforms. While these platforms have so far demonstrated high efficiency in measuring small model species like Arabidopsis thaliana, they have the drawback of limited adaptability to accommodate different plant sizes. As a result, the range of species that can be analyzed is restricted. This chapter presents our approach to analyze the photosynthetic parameters: ϕPSII and Fv/Fm for a panel of Brassicaceae species, including a high-photosynthesis species, Hirschfeldia incana, and the adaptations to the phenotyping platform that are required to accommodate this varied group of plants.

Nanoplastic toxicity induces metabolic shifts in Populus × euramericana cv. '74/76' revealed by multi-omics analysis.

There is increasing global concern regarding the pervasive issue of plastic pollution. We investigated the response of Populus × euramericana cv. '74/76' to nanoplastic toxicity via phenotypic, microanatomical, physiological, transcriptomic, and metabolomic approaches. Polystyrene nanoplastics (PS-NPs) were distributed throughout the test plants after the application of PS-NPs. Nanoplastics principally accumulated in the roots; minimal fractions were translocated to the leaves. In leaves, however, PS-NPs easily penetrated membranes and became concentrated in chloroplasts, causing thylakoid disintegration and chlorophyll degradation. Finally, oxidant damage from the influx of PS-NPs led to diminished photosynthesis, stunted growth, and etiolation and/or wilting. By integrating dual-omics data, we found that plants could counteract mild PS-NP-induced oxidative stress through the antioxidant enzyme system without initiating secondary metabolic defense mechanisms. In contrast, severe PS-NP treatments promoted a shift in metabolic pattern from primary metabolism to secondary metabolic defense mechanisms, an effect that was particularly pronounced during the upregulation of flavonoid biosynthesis. Our findings provide a useful framework from which to further clarify the roles of key biochemical pathways in plant responses to nanoplastic toxicity. Our work also supports the development of effective strategies to mitigate the environmental risks of nanoplastics by biologically immobilizing them in contaminated lands.

Influence of low-cost Thai leucoxene minerals on the growth, bioactive compounds, and antibacterial activities of Chrysanthemum indium L. cuttings in in vitro culture.

The effects of low-cost Thai leucoxene mineral (LM) at different concentrations (10, 20, 30, 40, 50, and 60 mg/L) on the growth and antibacterial properties of Chrysanthemum indium L. cuttings under in vitro were evaluated. The primary chemical composition of LM was approximately 86% titanium dioxide (TiO2), as determined by dispersive X-ray spectroscopy. The crystalline structure, shape, and size were investigated by X-ray diffraction and scanning electron microscopy. LM at 40 and 50 mg/L significantly increased plant height, leaf number, node number, and fresh and dry weight. These growth-promoting properties were accompanied by improved chlorophyll and carotenoid contents and antioxidant enzyme activities and reduced malondialdehyde levels. Additionally, LM treatment at 40 and 50 mg/L had positive effects on antibacterial activity, as indicated by the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. The high levels of phenolic compounds in the plants contributed to the MIC and MBC values. In conclusion, these findings provide evidence for the effectiveness of LM in enhancing the growth of Chrysanthemum plants in in vitro culture and improving their antibacterial abilities.

Potassium humate supplementation improves photosynthesis and agronomic and yield traits of foxtail millet.

Foxtail millet is a highly nutritious crop, which is widely cultivated in arid and semi-arid areas worldwide. Humic acid (HA), as a common plant growth regulator, is used as an organic fertilizer and feed additive in agricultural production. However, the impact of potassium humate KH on the photosynthetic rate and yield of foxtail millet has not yet been studied. We explored the effects of KH application on the morphology, photosynthetic ability, carbon and nitrogen metabolism, and yield of foxtail millet. A field experiment was performed using six concentrations of KH (0, 20, 40, 80, 160, and 320 kg ha-1) supplied foliarly at the booting stage in Zhangza 10 cultivar (a widely grown high-yield variety). The results showed that KH treatment increased growth, chlorophyll content (SPAD), photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs). In addition, soluble protein content, sugar content, and nitrate reductase activity increased in KH-treated plants. With increased KH concentration, the effects became more evident and the peak values of each factor were achieved at 80 kg ha-1. Photosynthetic rate showed significant correlation with SPAD, Tr, Gs, and soluble protein content, but was negatively correlated with intercellular CO2 concentration. Compared to that of the control, the yield of foxtail millet under the T2, T3, T4, and T5 (40, 80, 160, and 320 kg ha-1 of KH) treatments significantly increased by 6.0%, 12.7%, 10.5%, and 8.6%, respectively. Yield exhibited a significant positive correlation with Tr, Pn, and Gs. Overall, KH enhances photosynthetic rate and yield of foxtail millet, therefore it may be conducive to stable millet production. These findings may provide a theoretical basis for the green and efficient production of millet fields.

Both external and internal factors induce heterogeneity in senescing leaves of deciduous trees.

Autumn senescence is characterised by spatial and temporal heterogeneity. We show that senescing birch (Betula spp.) leaves had lower PSII activity (probed by the F V /F M chlorophyll a fluorescence parameter) in late autumn than in early autumn. We confirmed that PSII repair slows down with decreasing temperature, while rates of photodamage and recovery, measured under laboratory conditions at 20°C, were similar in these leaves. We propose that low temperatures during late autumn hinder repair and lead to accumulation of non-functional PSII units in senescing leaves. Fluorescence imaging of birch revealed that chlorophyll preferentially disappeared from inter-veinal leaf areas. These areas showed no recovery capacity and low non-photochemical quenching while green veinal areas of senescing leaves resembled green leaves. However, green and yellow leaf areas showed similar values of photochemical quenching. Analyses of thylakoids isolated from maple (Acer platanoides ) leaves showed that red, senescing leaves contained high amounts of carotenoids and α-tocopherol, and our calculations suggest that α-tocopherol was synthesised during autumn. Thylakoids isolated from red maple leaves produced little singlet oxygen, probably due to the high antioxidant content. However, the rate of PSII photodamage did not decrease. The data show that the heterogeneity of senescing leaves must be taken into account to fully understand autumn senescence.

Transcriptional and post-transcriptional regulation of chloroplast development by nuclear-localized XAP5 CIRCADIAN TIMEKEEPER.

Chlorophyll biosynthesis and breakdown, important cellular processes for photosynthesis, occur in the chloroplast. As a semi-autonomous organelle, chloroplast development is mainly regulated by nuclear-encoded chloroplast proteins and proteins encoded by itself. However, the knowledge of chloroplast development regulated by other organelles is limited. Here, we report that the nuclear-localized XAP5 CIRCADIAN TIMEKEEPER (XCT) is essential for chloroplast development in Arabidopsis. In this study, significantly decreased chlorophyll content phenotypes of cotyledons and subsequently emerging organs from shoot apical meristem were observed in xct-2. XCT is constitutively expressed in various tissues and localized in the nuclear with speckle patterns. RNA-seq analysis identified 207 differently spliced genes and 1511 differently expressed genes, in which chloroplast development-, chlorophyll metabolism- and photosynthesis-related genes were enriched. Further biochemical assays suggested that XCT was co-purified with the well-known splicing factors and transcription machinery, suggesting dual functions of XCT in gene transcription and splicing. Interestingly, we also found that the chlorophyll contents in xct-2 significantly decreased under high temperature and high light condition, indicating XCT integrates temperature and light signals to fine-tune the chlorophyll metabolism in Arabidopsis. Therefore, our results provide new insights into chloroplast development regulation by XCT, a nuclear-localized protein, at the transcriptional and post-transcriptional level.

PigmentHunter: A point-and-click application for automated chlorophyll-protein simulations.

Chlorophyll proteins (CPs) are the workhorses of biological photosynthesis, working together to absorb solar energy, transfer it to chemically active reaction centers, and control the charge-separation process that drives its storage as chemical energy. Yet predicting CP optical and electronic properties remains a serious challenge, driven by the computational difficulty of treating large, electronically coupled molecular pigments embedded in a dynamically structured protein environment. To address this challenge, we introduce here an analysis tool called PigmentHunter, which automates the process of preparing CP structures for molecular dynamics (MD), running short MD simulations on the nanoHUB.org science gateway, and then using electrostatic and steric analysis routines to predict optical absorption, fluorescence, and circular dichroism spectra within a Frenkel exciton model. Inter-pigment couplings are evaluated using point-dipole or transition-charge coupling models, while site energies can be estimated using both electrostatic and ring-deformation approaches. The package is built in a Jupyter Notebook environment, with a point-and-click interface that can be used either to manually prepare individual structures or to batch-process many structures at once. We illustrate PigmentHunter's capabilities with example simulations on spectral line shapes in the light harvesting 2 complex, site energies in the Fenna-Matthews-Olson protein, and ring deformation in photosystems I and II.

Bioavailability and Toxicity of nano Copper Oxide to Pakchoi (Brassica Campestris L.) as Compared with bulk Copper Oxide and Ionic Copper.

The increasing use of copper oxide nano particles (nCuO) as nano-fertilizers and pesticides have raised concerns over their impact on soil environment and agricultural products. In this study, two nCuO with different shapes, namely spherical nCuO (CuO NPs) and tubular nCuO (CuO NTs), were selected to investigate their bioavailability and toxicity to pakchoi in two soils with different properties. At the meantime, CuO bulk particles (CuO BPs) and Cu(NO3)2 were used for comparison. Results showed that all the Cu treatments increased the DTPA extractable (DTPA-Cu) concentrations in GD soil (acidic) more than in HN soil (alkaline). The DTPA-Cu concentrations increased in the order of Cu(NO3)2 ≈ CuO NPs > CuO BPs ≈ CuO NTs in GD soil and Cu(NO3)2 > CuO NPs > CuO BPs ≈ CuO NTs in HN soil. While for the contents of Cu in the aerial parts of pakchoi, the order is CuO NPs > Cu(NO3)2 > CuO NTs ≈ CuO BPs in GD soil and CuO NPs ≈ Cu(NO3)2 > CuO BPs ≈ CuO NTs in HN soil. Only CuO NPs reduced pakchoi biomass in GD soil. There are no significant difference among CuO NPs, CuO BPs, and Cu(NO3)2 in reducing the chlorophyll contents in pakchoi in HN soil, whereas in GD soil, CuO NPs and CuO BPs led to significantly lower chlorophyll contents in pakchoi compared to Cu(NO3)2. Additionally, CuO NPs and Cu(NO3)2 increased Mn and Mo in pakchoi leaf in HN soil, while increased Zn in pakchoi leaf in GD soil. These results indicated that CuO NPs showed higher or comparable toxicity and bioavailability to pakchoi compared with Cu(NO3)2 depending on soil properties, and nCuO are more easily to be transferred from roots to the aerial parts than CuO BPs and Cu(NO3)2.

Variability in the relationship between light scattering and chlorophyll a concentration in oligotrophic tropical regions of the Western Pacific Ocean.

It is important to determine the relationship between the concentration of chlorophyll a (Chla) and the inherent optical properties (IOPs) of ocean water to develop optical models and algorithms that characterize the biogeochemical properties and estimate biological pumping and carbon flux in this environment. However, previous studies reported relatively large variations in the particulate backscattering coefficient (bbp(λ)) and Chla from more eutrophic high-latitude waters to clear oligotrophic waters, especially in oligotrophic oceanic areas where these two variables have little covariation. In this study, we examined the variability of bbp(λ) and Chla in the euphotic layer in oligotrophic areas of the tropical Western Pacific Ocean and determined the sources of these variations by reassessment of in-situ measurements and the biogeochemical-argo (BGC-Argo) database. Our findings identified covariation of bbp(λ) and Chla in the water column below the deep Chla maximum (DCM) layer, and indicated that there was no significant correlation relationship between bbp(λ) and Chla in the upper layer of the DCM. Particles smaller than 3.2 µm that were in the water column above the DCM layer had a large effect on the bbp(λ) in the vertical profile, but particles larger than 3.2 µm and smaller than 10 µm had the largest effect on the bbp(λ) in the water column below the DCM layer. The contribution of non-algal particles (NAPs) to backscattering is up to 50%, which occurs in the water depth of 50 m and not consistent with the distribution of Chla. Phytoplankton and NAPs were modeled as coated spheres and homogeneous spherical particles to simulate the bbp(λ) of the vertical profile by Aden-Kerker method and Mie theory, and the results also indicated that the backscattering caused by particles less than 20 µm were closer to the measured data when they were below and above the DCM layer, respectively. This relationship also reflects the bbp(λ) of particles in the upper water was significantly affected particle size, but bbp(λ) in the lower water was significantly affected by Chla concentration. This effect may have relationship with phytoplankton photoacclimation and the relationship of a phytoplankton biomass maximum with particle size distribution in the water column according to the previous relevant studies. These characteristics also had spatial and seasonal variations due to changes of Chla concentration at the surface and at different depths. There was mostly a linear relationship between Chla and bbp(700) during winter. During other seasons, the relationship between these two variables was better characterized by a power function (or a logarithmic function) in the lower layer of the DCM. The spatial and vertical relationships between the bbp(λ) and Chla and the corresponding variations in the types of particles described in this study provide parameters that can be used for accurate estimation of regional geochemical processes.

Fulvic acid foliar application: a novel approach enhancing antioxidant capacity and nutritional quality of pistachio (Pistacia vera L.).

BACKGROUND: The global growth of pistachio production has prompted exploration into sustainable agricultural practices, on the application of humic substances such as fulvic acid in enhancing the quality of horticultural crops. The present study was carried out in Qom province, Iran, on 20 years old pistachio (Pistacia vera L. cv. Kaleh-Ghoochi) trees and investigated the impact of foliar spraying of fulvic acid at varying concentrations (1.5, 3, and 4.5 g L- 1) on the antioxidant and quality properties of pistachio. The different concentrations of fulvic acid were applied at two key stages: at the initiation of pistachio kernel formation (late June) and the development stage of pistachio kernel (late August), as well as at both time points. Following harvest at the horticulturally mature phase, various parameters, including total phenols, flavonoids, soluble proteins, soluble carbohydrate content, antioxidant capacity, and antioxidant enzyme activity, were assessed. RESULTS: Results indicated that foliar application of fulvic acid, particularly at 1.5 g L- 1 during both late June and August, effectively increased phenolic compounds (31.8%) and flavonoid content (24.53%). Additionally, this treatment also augmented antioxidant capacity and heightened the activity of catalase (CAT) (37.56%), ascorbate peroxidase (APX) (63.86%), and superoxide dismutase (SOD) (76.45%). Conversely, peroxidase (POX) (41.54%) activity was reduced in fulvic acid-treated nuts compared with controls. Moreover, the content of chlorophyll (45%) and carotenoids (46.7%) was enhanced using this organic fertilizer. In terms of mineral elements, the increment was observed in zinc (Zn) (58.23%) and potassium (K) (28.12%) amounts in treated nuts. Additionally, foliar application of fulvic acid led to elevated levels of soluble carbohydrates and proteins in treated nuts. CONCLUSIONS: In the present study, application of fulvic acid resulted in enhancement of antioxidant activity and quality traits of pistachio nut through an increase in total phenol, flavonoids, chlorophyll, carotenoids, K, Zn, and also activity of antioxidant enzymes. Therefore, use of fulvic acid emerges as a promising strategy to enhance the quality and nutritional attributes of pistachios, contributing to sustainable agricultural practices and improved crop outcomes.

Hormonal response to recurrent seasonal stress in coastal and mountain scabiouses growing in their natural habitat: linking ABA and jasmonates with photoprotection.

Plant species distribution across ecosystems is influenced by multiple environmental factors, and recurrent seasonal stress events can act as natural selection agents for specific plant traits and limit species distribution. For that, studies aiming at understanding how environmental constraints affect adaptive mechanisms of taxonomically closely related species are of great interest. We chose two Scabiosa species inhabiting contrasting environments: the coastal scabious S. atropurpurea, typically coping with hot-dry summers in a Mediterranean climate, and the mountain scabious S. columbaria facing cold winters in an oceanic climate. A set of functional traits was examined to assess plant performance in these congeneric species from contrasting natural habitats. Both S. atropurpurea and S. columbaria appeared to be perfectly adapted to their environment in terms of adjustments in stomatal closure, CO2 assimilation rate and water use efficiency over the seasons. However, an unexpected dry period during winter followed by the typical Mediterranean hot-dry summer forced S. atropurpurea plants to deploy a set of photoprotective responses during summer. Aside from reductions in leaf water content and Fv/Fm, photoprotective molecules (carotenoids, α-tocopherol and anthocyanins) per unit of chlorophyll increased, mostly as a consequence of a severe chlorophyll loss. The profiling of stress-related hormones (ABA, salicylic acid and jasmonates) revealed associations between ABA and the bioactive jasmonoyl-isoleucine with the underlying photoprotective response to recurrent seasonal stress in S. atropurpurea. We conclude that jasmonates may be used together with ABA as a functional trait that may, at least in part, help understand plant responses to recurrent seasonal stress in the current frame of global climate change.

[Transcriptional analysis of the molecular response of Arabidopsis to manganese stress and recovery].

Manganese (Mn) is an essential element for plants and plays a role in various metabolic processes. However, excess manganese can be toxic to plants. This study aimed to analyze the changes in various physiological activities and the transcriptome of Arabidopsis under different treatments: 1 mmol/L MnCl2 treatment for 1 day or 3 days, and 1 day of recovery on MS medium after 3 days of MnCl2 treatment. During the recovery phase, minor yellowing symptoms appeared on the leaves of Arabidopsis, and the content of chlorophyll and carotenoid decreased significantly, but the content of malondialdehyde and soluble sugar increased rapidly. Transcriptome sequencing data shows that the expression patterns of differentially expressed genes exhibit three major models: initial response model, later response model, recovery response model. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis identified several affected metabolic pathways, including plant hormone signal transduction mitosolysis activates protein kinase (MAPK) phytohormone signaling, phenylpropanoid biosynthesis, ATP binding cassette transporters (ABC transporter), and glycosphingolipid biosynthesis. Differential expressed genes (DEGs) involved in phenylpropanoid biosynthesis, ABC transporter, and glycosphingolipid biosynthesis, were identified. Sixteen randomly selected DEGs were validated through qRT-PCR and showed consistent results with RNA-seq data. Our findings suggest that the phenylpropanoid metabolic pathway is activated to scavenge reactive oxygen species, the regulation of ABC transporter improves Mn transport, and the adjustment of cell membrane lipid composition occurs through glycerophospholipid metabolism to adapt to Mn stress in plants. This study provides new insights into the molecular response of plants to Mn stress and recovery, as well as theoretical cues for cultivating Mn-resistant plant varieties.

ChloroSpec: A new in vivo chlorophyll fluorescence spectrometer for simultaneous wavelength- and time-resolved detection.

Chlorophyll fluorescence is a ubiquitous tool in basic and applied plant science research. Various standard commercial instruments are available for characterization of photosynthetic material like leaves or microalgae, most of which integrate the overall fluorescence signals above a certain cut-off wavelength. However, wavelength-resolved (fluorescence signals appearing at different wavelengths having different time dependent decay) signals contain vast information required to decompose complex signals and processes into their underlying components that can untangle the photo-physiological process of photosynthesis. Hence, to address this we describe an advanced chlorophyll fluorescence spectrometer - ChloroSpec - allowing three-dimensional simultaneous detection of fluorescence intensities at different wavelengths in a time-resolved manner. We demonstrate for a variety of typical examples that most of the generally used fluorescence parameters are strongly wavelength dependent. This indicates a pronounced heterogeneity and a highly dynamic nature of the thylakoid and the photosynthetic apparatus under actinic illumination. Furthermore, we provide examples of advanced global analysis procedures integrating this three-dimensional signal and relevant information extracted from them that relate to the physiological properties of the organism. This conveniently obtained broad range of data can make ChloroSpec a new standard tool in photosynthesis research.

Effects of Cu2O nanoparticles on the kinetic characteristics of rapid chlorophyll fluorescence induction and related genes in wheat seedlings.

Metal nanoparticles could be accumulated in soils, which threatens the ecological stability of crops. Investigating the effects of cuprous oxide nanoparticles (Cu2O-NPs) on photosystem Ⅱ (PSⅡ) of wheat seedling leaves holds considerable importance in comprehending the implications of Cu2O-NPs on crop photosynthesis. Following the hydroponic method, we investigated the effects of 0, 10, 50, 100, and 200 mg·L-1 Cu2O-NPs on chlorophyll fluorescence induction kinetics and photosynthetic-related genes in wheat seedlings of "Zhoumai 18". The results showed that, with the increases of Cu2O-NPs concentrations, chlorophyll contents in wheat leaves decreased, and the standardization of the OJIP curve showed a clearly K-phase (ΔK＞0). Cu2O-NPs stress increased the parameters of active PSⅡ reaction centers, including the absorption flux per active RC (ABS/RC), the trapping flux per active RC (TRo/RC), the electron transport flux per active RC (ETo/RC), and the dissipation flux per active RC (DIo/RC). Cu2O-NPs stress decreased the parameters of PSⅡ energy distribution ratio including the maximum quantum yield of PSⅡ (φPo), the quantum yield of electron transport from QA (φEo), and the probability that a trapped exciton moved an electron further than QA (Ψo), while increased the quantum ratio for heat dissipation (φDo). Moreover, there was a decrease in photosynthetic quantum yield Y(Ⅱ), photochemical quenching coefficient (qP), net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr) of leaves with the increases of Cu2O-NPs concentration. Under Cu2O-NPs stress, the expression levels of genes which included PSⅡ genes (PsbD, PsbP, Lhcb1), Rubisco large subunit genes (RbcL), cytochrome b6/f complex genes (PetD, Rieske), and ATP synthase genes (AtpA, AtpB, AtpE, AtpI) were downregulated. These results indicated that Cu2O-NPs stress altered the activity and structure of PSⅡ in wheat seedlings, affected the activity of PSⅡ reaction centers, performance parameters of PSⅡ donor and acceptor sides. PSⅡ related genes were downregulated and exhibited significant concentration effects.

[Effects of Biochar on Growth and Pollutant Accumulation of Lettuce in Soil Co-contaminated with Tetracycline and Copper].

Through lettuce potting experiments, the effects of different types of biochar (apple branch, corn straw, and modified sorghum straw biochar with phosphoric acid modification) on lettuce growth under tetracycline (TC) and copper (Cu) co-pollution were investigated. The results showed that compared with those under CK, the addition of biochar treatment significantly increased the plant height, root length, shoot fresh weight, and root fresh weight of lettuce (P < 0.05). The addition of different biochars significantly increased the nitrate nitrogen, chlorophyll, and soluble protein content in lettuce physiological indicators to varying degrees, while also significantly decreasing the levels of malondialdehyde, proline content, and catalase activity. The effects of biochar on lettuce physiological indicators were consistent during both the seedling and mature stages. Compared with those in CK, the addition of biochar resulted in varying degrees of reduction in the TC and Cu contents of both the aboveground and underground parts of lettuce. The aboveground TC and Cu levels decreased by 2.49%-92.32% and 12.79%-36.47%, respectively. The underground TC and Cu levels decreased by 12.53%-55.64% and 22.41%-42.29%, respectively. Correlation analysis showed that nitrate nitrogen, chlorophyll, and soluble protein content of lettuce were negatively correlated with TC content, whereas malondialdehyde, proline content, and catalase activity were positively correlated with TC content. The resistance genes of lettuce were positively correlated with TC content (P < 0.05). In general, modified biochar was found to be more effective in improving lettuce growth quality and reducing pollutant accumulation compared to unmodified biochar, with modified sorghum straw biochar showing the best remediation effect.

Transcriptomic analysis of hub genes regulating albinism in light- and temperature-sensitive albino tea cultivars 'Zhonghuang 1' and 'Zhonghuang 2'.

Albino tea cultivars have high economic value because their young leaves contain enhanced free amino acids that improve the quality and properties of tea. Zhonghuang 1 (ZH1) and Zhonghuang 2 (ZH2) are two such cultivars widely planted in China; however, the environmental factors and molecular mechanisms regulating their yellow-leaf phenotype remain unclear. In this study, we demonstrated that both ZH1 and ZH2 are light- and temperature-sensitive. Under natural sunlight and low-temperature conditions, their young shoots were yellow with decreased chlorophyll and an abnormal chloroplast ultrastructure. Conversely, young shoots were green with increased chlorophyll and a normal chloroplast ultrastructure under shading and high-temperature conditions. RNA-seq analysis was performed for high light and low light conditions, and pairwise comparisons identified genes exhibiting different light responses between albino and green-leaf cultivars, including transcription factors, cytochrome P450 genes, and heat shock proteins. Weighted gene coexpression network analyses of RNA-seq data identified the modules related to chlorophyll differences between cultivars. Genes involved in chloroplast biogenesis and development, light signaling, and JA biosynthesis and signaling were typically downregulated in albino cultivars, accompanied by a decrease in JA-ILE content in ZH2 during the albino period. Furthermore, we identified the hub genes that may regulate the yellow-leaf phenotype of ZH1 and ZH2, including CsGDC1, CsALB4, CsGUN4, and a TPR gene (TEA010575.1), which were related to chloroplast biogenesis. This study provides new insights into the molecular mechanisms underlying leaf color formation in albino tea cultivars.

High-Resolution Frequency-Domain Spectroscopic and Modeling Studies of Photosystem I (PSI), PSI Mutants and PSI Supercomplexes.

Photosystem I (PSI) is one of the two main pigment-protein complexes where the primary steps of oxygenic photosynthesis take place. This review describes low-temperature frequency-domain experiments (absorption, emission, circular dichroism, resonant and non-resonant hole-burned spectra) and modeling efforts reported for PSI in recent years. In particular, we focus on the spectral hole-burning studies, which are not as common in photosynthesis research as the time-domain spectroscopies. Experimental and modeling data obtained for trimeric cyanobacterial Photosystem I (PSI3), PSI3 mutants, and PSI3-IsiA18 supercomplexes are analyzed to provide a more comprehensive understanding of their excitonic structure and excitation energy transfer (EET) processes. Detailed information on the excitonic structure of photosynthetic complexes is essential to determine the structure-function relationship. We will focus on the so-called "red antenna states" of cyanobacterial PSI, as these states play an important role in photochemical processes and EET pathways. The high-resolution data and modeling studies presented here provide additional information on the energetics of the lowest energy states and their chlorophyll (Chl) compositions, as well as the EET pathways and how they are altered by mutations. We present evidence that the low-energy traps observed in PSI are excitonically coupled states with significant charge-transfer (CT) character. The analysis presented for various optical spectra of PSI3 and PSI3-IsiA18 supercomplexes allowed us to make inferences about EET from the IsiA18 ring to the PSI3 core and demonstrate that the number of entry points varies between sample preparations studied by different groups. In our most recent samples, there most likely are three entry points for EET from the IsiA18 ring per the PSI core monomer, with two of these entry points likely being located next to each other. Therefore, there are nine entry points from the IsiA18 ring to the PSI3 trimer. We anticipate that the data discussed below will stimulate further research in this area, providing even more insight into the structure-based models of these important cyanobacterial photosystems.

The responses of pepper plants to nitrogen form and dissolved oxygen concentration of nutrient solution in hydroponics.

BACKGROUND: The presence of oxygen in the growth medium is absolutely essential for root development and the overall metabolic processes of plants. When plants do not have an adequate oxygen supply for respiration, they can experience a condition known as hypoxia. In order to investigate the impact of different nitrogen forms and varying oxygen levels in nutrient solutions on the growth, photosynthesis, and chlorophyll fluorescence parameters of bell pepper plants, a comprehensive study was conducted. The experiment was designed as a factorial experiment, considering two main factors: nitrogen forms (calcium nitrate and ammonium sulfate) with a fixed nitrogen concentration of 5 mM, and the oxygen levels of the nutrient solutions (ranging from 1.8 ± 0.2 to 5.3 ± 0.2 mg. L-1). RESULTS: The study examined the effects of nitrogen (NH4+ and NO3-) application on various parameters of vegetative growth. The results demonstrated that the use of ammonium (NH4+) led to a reduction in the most measured parameters, including the fresh and dry mass of both the root and shoot, at low O2 concentrations of 1.8 ± 0.2; 2.6 ± 0.2 and 3.8 ± 0.2 mg. L-1. However, an interesting observation was made regarding the impact of oxygen levels on root growth in plants grown with nitrate (NO3-). Specifically, the highest levels of oxygen significantly increased root growth in NO3--fed plants. Additionally, the application of NH4+ resulted in an increase in chlorophyll concentration in the leaves, particularly when combined with high oxygen levels in the nutrient solution. On the other hand, leaves of plants fed with NO3- exhibited higher photosynthetic rate (A), intrinsic water use efficiency (iWUE), and instantaneous carboxylation efficiency (A/Ci) compared to those fed with NH4+. Furthermore, it was found that NO3--fed plants displayed the highest instantaneous carboxylation efficiency at oxygen levels of 3.8 and 5.3 mg. L-1, while the lowest efficiency was observed at oxygen levels of 1.8 and 2.6 mg. L-1. In contrast, NH4+-grown plants exhibited a higher maximal quantum yield of PSII photochemistry (Fv/Fm), as well as increased variable fluorescence (Fv) and maximum fluorescence (Fm), compared to NO3--grown plants. Interestingly, the NO3--fed plants showed an increase in Fv/Fm, Fv, and Fm with the elevation of oxygen concentration in the nutrient solution up to 5.3 mg. L-1. CONCLUSION: This study showed that, the growth and photosynthesis parameters in bell pepper plants are sensitive to oxygen stress in floating hydroponic culture. Therefore, the oxygen level in the nutrient solution must not be lower than 3.8 and 5.3 mg. L-1 in NH4+ and NO3- -supplied culture media or nutrient solutions, respectively.

Effect of Arbuscular Mycorrhizal Fungi (AMF) on photosynthetic characteristics of cotton seedlings under saline-alkali stress.

The study aimed to find the best Arbuscular Mycorrhizal Fungi (AMF) strain for cotton growth in Xinjiang's salinity and alkali conditions. Cotton (Xinluzao 45) was treated with Funneliformis mosseae (GM), Rhizophagus irregularis (GI), and Claroideoglomus etunicatum (GE) as treatments, while untreated cotton served as the control (CK). Salinity stress was applied post-3-leaf stage in cotton. The study analyzed cotton's reactions to diverse saline-alkali stresses, focusing on nutrient processes and metabolism. By analyzing the growth and photosynthetic characteristics of plants inoculated with Funneliformis mosseae to evaluate its salt tolerance. Saline-alkali stress reduced chlorophyll and hindered photosynthesis, hampering cotton growth. However, AMF inoculation mitigated these effects, enhancing photosynthetic rates, CO2 concentration, transpiration, energy use efficiency, and overall cotton growth under similar stress levels. GM and GE treatments yielded similar positive effects. AMF inoculation enhanced cotton plant height and biomass. In GM treatment, cotton exhibited notably higher root length than other treatments, showing superior growth under various conditions. In summary, GM-treated cotton had the highest infection rate, followed by GE-treated cotton, with GI-treated cotton having the lowest rate (GM averaging 0.95). Cotton inoculated with Funneliformis mosseae, Rhizophagus irregularis, and Claroideoglomus etunicatum juvenile showed enhanced chlorophyll and photosynthetic levels, reducing salinity effects. Funneliformis mosseae had the most significant positive impact.