Cell wall structure and composition is affected by light quality in tomato seedlings

Individual and interactive effects of temperature and blue light on canola growth, lignin biosynthesis and methane emissions

It is now well documented that plants produce methane (CH4) under aerobic conditions. However, the mechanisms of methane production in plants, its potential precursors, and the factors that are involved in the process are not fully understood. Few studies have considered the effects of blue light on methane emissions from plants; however, the combined effects of temperature and blue light have not been studied. We studied the effects of two temperature regimes (22/18 °C and 28/24 °C; 16 h light/8 h dark), and three blue light levels (0, 4, and 8 mW cm-2; 400-500 nm) on the growth, lignin, and methane emissions of canola (Brassica napus). Plants were grown under experimental conditions for three weeks, and then methane, monolignols and other plant traits, including growth, biomass, growth index, photosynthesis, chlorophyll fluorescence, and photosynthetic pigments, were measured. Blue light significantly increased methane emissions, stem height, and growth rate, but decreased stem diameter, leaf number and area, biomass, specific leaf mass, leaf area ratio, shoot/root mass ratio, photosynthetic pigments, sinapyl alcohol, and coniferyl aldehyde. Higher temperature significantly decreased stem diameter, non-photochemical quenching, sinapyl alcohol, and coniferyl aldehyde. Methane emission was negatively correlated with plant dry mass, leaf area per plant, and maximum quantum yield of photosystem II. However, no significant relationships were found between methane and monolignols. In conclusion, plants emitted more methane under stress conditions; however, further studies are required to understand the potential precursors of methane and the mechanism of its synthesis in plants.

Hyperspectral and Chlorophyll Fluorescence Analyses of Comparative Leaf Surfaces Reveal Cellular Influences on Leaf Optical Properties in Tradescantia Plants

The differential effects of cellular and ultrastructural characteristics on the optical properties of adaxial and abaxial leaf surfaces in the genus Tradescantia highlight the intricate relationships between cellular arrangement and pigment distribution in the plant cells. We examined hyperspectral and chlorophyll a fluorescence (ChlF) kinetics using spectroradiometers and optical and electron microscopy techniques. The leaves were analysed for their spectral properties and cellular makeup. The biochemical compounds were measured and correlated with the biophysical and ultrastructural features. The main findings showed that the top and bottom leaf surfaces had different amounts and patterns of pigments, especially anthocyanins, flavonoids, total phenolics, chlorophyll-carotenoids, and cell and organelle structures, as revealed by the hyperspectral vegetation index (HVI). These differences were further elucidated by the correlation coefficients, which influence the optical signatures of the leaves. Additionally, ChlF kinetics varied between leaf surfaces, correlating with VIS-NIR-SWIR bands through distinct cellular structures and pigment concentrations in the hypodermis cells. We confirmed that the unique optical properties of each leaf surface arise not only from pigmentation but also from complex cellular arrangements and structural adaptations. Some of the factors that affect how leaves reflect light are the arrangement of chloroplasts, thylakoid membranes, vacuoles, and the relative size of the cells themselves. These findings improve our knowledge of the biophysical and biochemical reasons for leaf optical diversity, and indicate possible implications for photosynthetic efficiency and stress adaptation under different environmental conditions in the mesophyll cells of Tradescantia plants.

Blue light regulated lignin and cellulose content of soybean petioles and stems under low light intensity

To improve light harvest and plant structural support under low light intensity, it is useful to investigate the effects of different ratios of blue light on petiole and stem growth. Two true leaves of soybean seedlings were exposed to a total light intensity of 200μmolm-2 s-1 , presented as either white light or three levels of blue light (40μmolm-2 s-1 , 67μmolm-2 s-1 and 100μmolm-2 s-1 ) for 15days. Soybean petioles under the low blue light treatment upregulated expression of genes relating to lignin metabolism, enhancing lignin content compared with the white light treatment. The low blue light treatment had high petiole length, increased plant height and improved petiole strength arising from high lignin content, thus significantly increasing leaf dry weight relative to the white light treatment. Compared with white light, the treatment with the highest blue light ratio reduced plant height and enhanced plant support through increased cellulose and hemicellulose content in the stem. Under low light intensity, 20% blue light enhanced petiole length and strength to improve photosynthate biomass; whereas 50% blue light lowered plants' centre of gravity, preventing lodging and conserving carbohydrate allocation.

Functional Meta-Analysis of the Proteomic Responses of Arabidopsis Seedlings to the Spaceflight Environment Reveals Multi-Dimensional Sources of Variability across Spaceflight Experiments

The human quest for sustainable habitation of extraterrestrial environments necessitates a robust understanding of life's adaptability to the unique conditions of spaceflight. This study provides a comprehensive proteomic dissection of the Arabidopsis plant's responses to the spaceflight environment through a meta-analysis of proteomics data from four separate spaceflight experiments conducted on the International Space Station (ISS) in different hardware configurations. Raw proteomics LC/MS spectra were analyzed for differential expression in MaxQuant and Perseus software. The analysis of dissimilarities among the datasets reveals the multidimensional nature of plant proteomic responses to spaceflight, impacted by variables such as spaceflight hardware, seedling age, lighting conditions, and proteomic quantification techniques. By contrasting datasets that varied in light exposure, we elucidated proteins involved in photomorphogenesis and skotomorphogenesis in plant spaceflight responses. Additionally, with data from an onboard 1 g control experiment, we isolated proteins that specifically respond to the microgravity environment and those that respond to other spaceflight conditions. This study identified proteins and associated metabolic pathways that are consistently impacted across the datasets. Notably, these shared proteins were associated with critical metabolic functions, including carbon metabolism, glycolysis, gluconeogenesis, and amino acid biosynthesis, underscoring their potential significance in Arabidopsis' spaceflight adaptation mechanisms and informing strategies for successful space farming.

Identification of Differentially Expressed lncRNAs in Response to Blue Light and Expression Pattern Analysis of Populus tomentosa Hybrid Poplar 741

Poplar is an important shelterbelt, timber stand, and city tree species that has been the focus of forestry research. The regulatory role of the long non-coding RNA molecule (lncRNA; length > 200 nt) has been a research hotspot in plants. In this study, seedlings of 741 poplar were irradiated with LED blue and white light, and the Illumina HiSeq 2000 sequencing platform was used to identify lncRNAs. |logFC| > 1 and p < 0.05 were considered to indicate differentially expressed lncRNAs, and nine differentially expressed lncRNAs were screened, the target genes of which were predicted, and three functionally annotated target genes were obtained. The differentially expressed lncRNAs were identified as miRNA targets. Six lncRNAs were determined to be target sites for twelve mRNAs in six miRNA families. LncRNAs and their target genes, including lncRNA MSTRG.20413.1-ptc-miR396e-5p-GRF9, were verified using quantitative real-time polymerase chain reaction analysis, and the expression patterns were analyzed. The analysis showed that the ptc-miR396e-5p expression was downregulated, while lncRNA MSTRG.20413.1 and GRF9 expression was upregulated, after blue light exposure. These results indicate that lncRNAs interact with miRNAs to regulate gene expression and affect plant growth and development.

Enhancing Pigment Phenotyping and Classification in Lettuce through the Integration of Reflectance Spectroscopy and AI Algorithms

In this study, we investigated the use of artificial intelligence algorithms (AIAs) in combination with VIS-NIR-SWIR hyperspectroscopy for the classification of eleven lettuce plant varieties. For this purpose, a spectroradiometer was utilized to collect hyperspectral data in the VIS-NIR-SWIR range, and 17 AIAs were applied to classify lettuce plants. The results showed that the highest accuracy and precision were achieved using the full hyperspectral curves or the specific spectral ranges of 400-700 nm, 700-1300 nm, and 1300-2400 nm. Four models, AdB, CN2, G-Boo, and NN, demonstrated exceptional R² and ROC values, exceeding 0.99, when compared between all models and confirming the hypothesis and highlighting the potential of AIAs and hyperspectral fingerprints for efficient, precise classification and pigment phenotyping in agriculture. The findings of this study have important implications for the development of efficient methods for phenotyping and classification in agriculture and the potential of AIAs in combination with hyperspectral technology. To advance our understanding of the capabilities of hyperspectroscopy and AIs in precision agriculture and contribute to the development of more effective and sustainable agriculture practices, further research is needed to explore the full potential of these technologies in different crop species and environments.

Data-Independent Acquisition Proteomics Reveals the Effects of Red and Blue Light on the Growth and Development of Moso Bamboo (Phyllostachys edulis) Seedlings

Moso bamboo is a rapidly growing species with significant economic, social, and cultural value. Transplanting moso bamboo container seedlings for afforestation has become a cost-effective method. The growth and development of the seedlings is greatly affected by the quality of light, including light morphogenesis, photosynthesis, and secondary metabolite production. Therefore, studies on the effects of specific light wavelengths on the physiology and proteome of moso bamboo seedlings are crucial. In this study, moso bamboo seedlings were germinated in darkness and then exposed to blue and red light conditions for 14 days. The effects of these light treatments on seedling growth and development were observed and compared through proteomics analysis. Results showed that moso bamboo has higher chlorophyll content and photosynthetic efficiency under blue light, while it displays longer internode and root length, more dry weight, and higher cellulose content under red light. Proteomics analysis reveals that these changes under red light are likely caused by the increased content of cellulase CSEA, specifically expressed cell wall synthetic proteins, and up-regulated auxin transporter ABCB19 in red light. Additionally, blue light is found to promote the expression of proteins constituting photosystem II, such as PsbP and PsbQ, more than red light. These findings provide new insights into the growth and development of moso bamboo seedlings regulated by different light qualities.

Rapid Quantification Method for Yield, Calorimetric Energy and Chlorophyll a Fluorescence Parameters in Nicotiana tabacum L. Using Vis-NIR-SWIR Hyperspectroscopy

High-throughput and large-scale data are part of a new era of plant remote sensing science. Quantification of the yield, energetic content, and chlorophyll a fluorescence (ChlF) remains laborious and is of great interest to physiologists and photobiologists. We propose a new method that is efficient and applicable for estimating photosynthetic performance and photosystem status using remote sensing hyperspectroscopy with visible, near-infrared and shortwave spectroscopy (Vis-NIR-SWIR) based on rapid multivariate partial least squares regression (PLSR) as a tool to estimate biomass production, calorimetric energy content and chlorophyll a fluorescence parameters. The results showed the presence of typical inflections associated with chemical and structural components present in plants, enabling us to obtain PLSR models with R2P and RPDP values greater than >0.82 and 3.33, respectively. The most important wavelengths were well distributed into 400 (violet), 440 (blue), 550 (green), 670 (red), 700−750 (red edge), 1330 (NIR), 1450 (SWIR), 1940 (SWIR) and 2200 (SWIR) nm operating ranges of the spectrum. Thus, we report a methodology to simultaneously determine fifteen attributes (i.e., yield (biomass), ΔH°area, ΔH°mass, Fv/Fm, Fv’/Fm’, ETR, NPQ, qP, qN, ΦPSII, P, D, SFI, PI(abs), D.F.) with high accuracy and precision and with excellent predictive capacity for most of them. These results are promising for plant physiology studies and will provide a better understanding of photosystem dynamics in tobacco plants when a large number of samples must be evaluated within a short period and with remote acquisition data.

Comprehensive transcriptomic and metabolomic profiling reveals the differences between alfalfa sprouts germinated with or without light exposure

Alfalfa sprouts are among the most nutritionally rich foods, and light exposure is a critical factor in determining their biomass and quality. However, detailed metabolic and molecular differences between yellow and green alfalfa sprouts remain unclear. In this study, comprehensive metabolomic and transcriptomic analyses were integrated to evaluate the nutrient composition of alfalfa sprouts during germination with or without light exposure. Differentially expressed genes and differentially accumulated metabolites in green and yellow alfalfa sprouts were significantly enriched in secondary metabolic pathways, such as the isoflavonoid biosynthesis pathway. Green alfalfa sprouts contained a wide variety of lipids, flavonoids, phenolic acids, and terpenoids, among which the top three upregulated were calycosin, methyl gallate, and epicatechin 3-gallate, whereas yellow alfalfa sprouts contained relatively more isoquercitrin. These results provide new insights into the nutritional value and composition of alfalfa sprouts under different germination regimes.

Simple, Fast and Efficient Methods for Analysing the Structural, Ultrastructural and Cellular Components of the Cell Wall

Plant cell walls are a fundamental component of plant biology and play an essential role in plant growth and development. The metabolic components of the cell wall can be investigated in a fast, simple, and highly efficient manner using various and distinct microscopy techniques. Here, we report implementing a flowchart to analyse tobacco plants’ structural, ultrastructural, and metabolic components supplemented with far-red light. In addition, biochemical components, such as lignin, cellulose, phenolic compounds, and reducing sugars, present in the plant cell walls were quantified using light, fluorescence, and electron microscopy. Our data were generated from samples prepared via tissue fixation, incorporation in resins, and slicing using microtomes. Moreover, we have used routine staining and contrast techniques to characterise plant cell walls. Here, we describe several protocols that use classic and modern techniques as well as qualitative and quantitative analytical methods to study cell walls, enabling the plant research community to understand and select the most suitable methods for the microscopic analysis of metabolic components. Finally, we discuss specific ideas aimed at new students of plant anatomy and microscopy. This research not only described the structural, ultrastructural, and metabolic components of the plant cell wall, but also explained the strategies for understanding cellular development.

Phytochrome A Mediates the Disassembly of Processing Bodies in Far-Red Light

Phytochromes are red- and far-red light receptors that control the growth and development of plants, enabling them to respond adequately to changing light conditions. It has been shown that halted mRNAs stored in RNA granules called processing bodies are released upon light perception and contribute to the adaptation to the light environment. However, the photophysiological background of this process is largely unknown. We found that light of different wavelengths can trigger the disassembly of processing bodies in a dose- and time-dependent manner. We show that phytochromes control this process in red- and far-red light and that cytoplasmic phytochrome A is sufficient and necessary for the far-red light-induced disassembly of processing bodies. This adds a novel, unexpected cytoplasmic function to the processes controlled by phytochrome A. Overall, our findings suggest a role of phytochromes in the control of translationally halted mRNAs that are stored in processing bodies. We expect our findings to facilitate understanding of how light and environmental cues control the assembly and disassembly of processing bodies, which could have broader implications for the regulation of non-membranous organelles in general.

Irradiance-driven 20-hydroxyecdysone production and morphophysiological changes in Pfaffia glomerata plants grown in vitro

Pfaffia glomerata possesses potential pharmacological and medicinal properties, mainly owing to the secondary metabolite 20-hydroxyecdysone (20E). Increasing production of biomass and 20E is important for industrial purposes. This study aimed to evaluate the influence of irradiance on plant morphology and production of 20E in P. glomerata grown in vitro. Nodal segments of accessions 22 and 43 (Ac22 and Ac43) were inoculated in culture medium containing MS salts and vitamins. Cultures were maintained at 25 ± 2 °C under a 16-h photoperiod and subjected to irradiance treatments of 65, 130, and 200 μmol m^-2 s^-1 by fluorescent lamps. After 30 days, growth parameters, pigment content, stomatal density, in vitro photosynthesis, metabolites content, and morphoanatomy were assessed. Notably, Ac22 plants exhibited 10-fold higher 20E production when cultivated at 200 μmol m^-2 s^-1 than at 65 μmol m^-2 s^-1, evidencing the importance of light quantity for the accumulation of this metabolite. 20E production was twice as high in Ac22 as in Ac43 plants although both accessions responded positively to higher irradiance. Growth under 200 μmol m^-2 s^-1 stimulated photosynthesis and consequent biomass accumulation, but lowered carotenoids and anthocyanins. Furthermore, increasing irradiance enhanced the number of palisade and spongy parenchyma cells, enhancing the overall growth of P. glomerata. Graphical abstract.