Chl Content Research Articles

Investigating the impact of silencing an RNA-binding protein gene SlRBP1 on tomato photosynthesis through RNA-sequencing analysis

Photosynthesis in plants directly affects the synthesis and accumulation of organic matter, which directly influences crop yield. RNA-binding proteins (RBPs) are involved in the regulation of a variety of physiological functions in plants, while the functions of RBPs in photosynthesis have not been clearly elucidated. To investigate the effect of a glycine-rich RNA-binding protein (SlRBP1) in tomato on plant photosynthesis, a stably inherited SlRBP1 silenced plant in Alisa Craig was obtained by plant tissue culture using artificial small RNA interference. It turns out that the size of the tomato fruit was reduced and leaves significantly turned yellow. Chlorophyll(Chl) content measurement, Chl fluorescence imaging and chloroplast transmission electron microscopy revealed that the chloroplast morphology and structure of the leaves of tomato amiR-SlRBP1 silenced plants were disrupted, and the chlorophyll content was significantly reduced. Measurement of photosynthesis rate of wild-type and amiR-SlRBP1 silenced plants in the same period demonstrated that the photosynthetic rate of these plants was significantly reduced, and analysis of RNA-seq data indicated that silencing of SlRBP1 significantly reduced the expression of photosynthesis-related genes, such as PsaE, PsaL, and PsbY, and affected the yield of tomato fruits through photosynthesis.

Environmental characteristics and major factors controlling chlorophyll a in three seamounts in the Subtropical Western Pacific Ocean

Seamounts interacting with oceanic currents created “seamount effect”, which could enhance the primary productivity in the euphotic zone. However, a large number of seamounts have not been investigated. In this study, the sectional distributions of temperature, salinity, dissolved inorganic nutrients, dissolved oxygen (DO), pH and chlorophyll a (Chl a) in three seamounts in the Subtropical Western Pacific Ocean (SWPO), named NA, NLG and MP4, were investigated. Consistent with no uplifts of isotherms and isohalines above three seamounts, the uplifts of the concentrations of dissolved inorganic nutrients and Chl a were unobvious, indicating that there was no “seamount effect” in these seamounts. Comparing with NA and MP4 seamounts, NLG seamount had higher salinity and lower temperature. However, the concentrations of inorganic nutrients and Chl a from surface to the subsurface chlorophyll maximum layer of NA and MP4 seamount were higher than those of NLG seamount. Meanwhile, due to the presence of tropic storm and cold eddy during the investigated period, the hydrological conditions there became more complex. Furthermore, Generalized Additive Models (GAMs) were used to infer the underlying factors controlling bottom-up effect on phytoplankton biomass in three seamounts. This study investigated the mechanism about the bottom-up effect on phytoplankton in seamount environment and provided basic information for future research on seamount ecosystem.

Silicon and titanium nanoparticles modulated drought and chromium toxicity by adjusting physio-biochemical attributes and fatty acid profiles of black cumin (Nigella sativa L.).

Drought and chromium (Cr) stress are the main environmental issues affecting plant performance. Although the positive effects of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles (NPs) are used as a promising strategy to control abiotic stresses; their synergic effects on controlling drought and Cr toxicity are unknown. This study aimed to investigate the effects of foliar applications of SiO2 (200 mg L-1) and TiO2 (60 mg L-1) NPs on growth, chlorophyll (Chl) content, lipid peroxidation, antioxidant enzyme, and fatty acid profile of black cumin (Nigella sativa L.) under drought (soil moisture at 50% field capacity (FC) and Cr toxicity as K2Cr2O7 at 10 mg L-1. The results showed that drought and Cr stress significantly reduced growth and Chl a + b, but increased malondialdehyde (MDA), electrolyte leakage (EL), and the activity of antioxidant enzymes. The use of NPs particularly SiO2 NPs modulated drought and Cr stress through enhancing Chl content and alleviating MDA, EL, and antioxidant activities. Under drought stress, SiO2 NPs enhanced shoot weight (26%), root weight (25%), seed yield (36%), Chl content (26%), but lowered MDA (22%), EL (14%), catalase (CAT, 32%), and superoxide dismutase (SOD, 33%) activity relative to non-NP application. The main changes in fatty acid profile corresponded to abiotic stresses, where they increased polyunsaturated fatty acids (PUFAs) but decreased monounsaturated fatty acids (MUFAs). Multivariate analysis showed that plant weight, seed yield, Cl content, and oleic acid negatively correlated with MDA, EL, antioxidant enzymes, and linoleic acid. In total, the use of SiO2 is recommended for modulating drought and Cr stress to reach the maximum seed yield of black cumin and a healthy fatty acid profile.

Transcriptomic, metabolomic, and physiological analysis of two varieties of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that differ in their storability

The storability of two different varieties of Chinese cabbage was evaluated. Results indicated that' Beijing New No.3′ (N3) exhibited longer storage life and better postharvest quality than' Beijing New No.1′ (N1). Relative to N1, N3 had a lower rate of fresh weight loss and rot development during the latter period of storage (125 days). Ethylene generation and the respiration rate of N3 cabbage were also lower than they were in N1 cabbage over the entire storage period. Chlorophyll (Chl) content was lower in N3 cabbage and the ACS, ACO and ACC enzyme activity were also lower than those in N1 cabbage. Additionally, the relative expression level of COL1, JAZ, MYC2, LOX, ACS, ACO, EBF, EIN3, ERF, and MKK in N1 Chinese cabbage increased, during storage in both varieties, while the relative expression of CDPK, COL1, CAML, and PAL decreased. These results provide valuable information on the storability and quality of Chinese cabbage, especially in relationship to plant hormone levels. The collective data indicate that N3 Chinese cabbage has better storability and postharvest quality than N1.

Physiological cost of Ulva lactuca under combined pressure of nutrient-oxytetracycline: One potential formation and maintenance mechanism of Ulva sp. green tide

Environmental pollution is considered to lead to Ulva sp. green tides. Nevertheless, nutrients with high concentrations inhibit algae which may be damaged by antibiotics, such as OTC (oxytetracycline). Thus, Ulva sp. algae might pay a physiological cost under nutrient-OTC combined pressures. If this hypothesis is confirmed, Ulva sp. algae cannot easily form green tides, or green tides are difficult to maintain. To test this hypothesis, an uniform design experiment during which OTC, ammonia (NH4-N) and phosphate (PO4-P) were factors was set to simulate nutrient-OTC combined pressures, and Ulva lactuca was exposed to the pressures for 96 h. The TN (total nitrogen, CTN) or TP (total phosphorus, CTP) content in U. lactuca increased with increasing nutrient concentrations, as CTN = 21.206±1.000+ 1.227±0.418NH4-N × PO4-P (R2 = 0.282, p < 0.05) and CTP = 1.886±0.266+ 0.877±0.126PO4-P (R2 = 0.689, p < 0.05), respectively. The increase in dry weight of U. lactuca (Wdry) had a relationship with combined pressures, Wdry = 0.011±0.029 - 0.036±0.014PO4-P (R2 = 0.243, p < 0.05), i.e., the algal growth was inhibited by increasing PO4-P concentration. The SOD (Superoxide dismutase) activity (ASOD) was stimulated by OTC, as ASOD = 127.868±8.741+9.587±4.179 OTC (R2 = 0.193, p < 0.05). The contents of Chl a and b (Ca and Cb) were negatively affected by OTC or PO4-P with high concentration, as Ca = 0.566±0.042 - 0.024±0.022 OTC × PO4-P (R2 = 0.179, p < 0.05) and Cb = 0.512±0.043–0.044±0.020PO4-P (R2 = 0.180, p < 0.05). Thus, too high concentrations of PO4-P or OTC may hinder the formation and maintenance of Ulva sp. green tides.

Influence of weather conditions on the dynamics of summer phytoplankton in the Kuibyshev reservoir

Based on observation data in the summer of 2019 and 2021, an assessment was made of changes in abiotic characteristics and chlorophyll (Chl) content in the Kuibyshev Reservoir. Regular observations were carried out at the outlet section of the reservoir (Zhigulevsky hydroelectric complex) under conditions of complete mixing of water masses. The main goal of the study is to assess the influence of abiotic factors on the chlorophyll content and the mass development of cyanobacteria. It has been established that the main influencing factors are thermal regime and weather conditions. 2019 is characterized as “cold”. The total number of days with water temperatures above 22 °C was only 11. The degree of favorability was low (23 °C ˃ t ˃ 22 °C). 2021 characterized as “warm”. The total number of days with water temperatures above 22 °C was 72. The degree of favorability varied widely: from low (23 °C ˃ t ˃ 22 °C) to extreme high (t ˃ 26 °C). The most favorable year for the mass development of cyanobacteria was 2021, when the Chl content over the summer period was 7.2 μg/dm3. The least favorable year was 2019, when the Chl content was 1.4 μg/dm3. Seasonally, the temperature optimum was observed annually in July. The Chl content in July 2021 was 12.6 μg/dm3, and in July 2019 – 1.8 μg/dm3. Significant variability in chlorophyll content is due to synoptic cyclicity and changing weather conditions. The established influence of thermal regime and weather conditions on the content of chlorophyll suggests that in conditions of global warming, the process of mass development of cyanobacteria is expected to intensify, which will negatively affect the ecological state and water quality of the Kuibyshev Reservoir.

Влияние погодных условий на процесс массового развития цианобактерий в Куйбышевском водохранилище

According to observation data in the summer period 2016-2021. The interannual variability of weather conditions, water temperature and chlorophyll (Chl) content in the Kuibyshev Reservoir was considered. Regular observations were carried out at the outlet section of the reservoir (Zhigulevsky hydroelectric complex) under conditions of complete mixing of water masses. It has been established that the main factors influencing the process of mass development of cyanobacteria (MDC) are thermal regime and weather conditions. With increasing water temperature, the interval and degree of favorable activity of cyanobacteria increases. Over a 6-year period, the average interval was 44 days, the largest was 72 days, and the smallest was 11 days. The degree of favorability varied widely: from low (23 °С ˃ t ˃ 22 °С) to extreme high (t ˃ 26 °С). The most favorable years for the MRC process were 2016 and 2021, when the Chl content during the summer period was 6.2 and 7.2 μg/dm3, respectively. The least favorable years were 2017 and 2019, when the Chl content during the summer period was 0.6 and 1.4 μg/dm3, respectively. Seasonally, the temperature optimum was observed annually in July. The Chl content in July 2021 was 12.6 μg/dm3, and in the cold July 2017 – 0.7 μg/dm3. Significant variability of the MRC process is due to synoptic cyclicity and changing weather conditions. The established influence of thermal regime and weather conditions on the content of chlorophyll suggests that in conditions of global warming, the process of mass development of cyanobacteria is expected to intensify, which will negatively affect the ecological state and water quality of the Kuibyshev Reservoir.

Cytonuclear interactions modulate the plasticity of photosynthetic rhythmicity and growth in wild barley.

In plants, the contribution of the plasmotype (mitochondria and chloroplast) in controlling the circadian clock plasticity and possible consequences on cytonuclear genetic makeup have yet to be fully elucidated. A genome-wide association study in the wild barley (Hordeum vulgare ssp. spontaneum) B1K collection identified overlap with our previously mapped DRIVERS OF CLOCKS (DOCs) loci in wild-cultivated interspecific population. Moreover, we identified non-random segregation and epistatic interactions between nuclear DOCs loci and the chloroplastic RpoC1 gene, indicating an adaptive value for specific cytonuclear gene combinations. Furthermore, we show that DOC1.1, which harbours the candidate SIGMA FACTOR-B (SIG-B) gene, is linked with the differential expression of SIG-B and CCA1 genes and contributes to the circadian gating response to heat. High-resolution temporal growth and photosynthesis measurements of B1K also link the DOCs loci to differential growth, Chl content and quantum yield. To validate the involvement of the Plastid encoded polymerase (PEP) complex, we over-expressed the two barley chloroplastic RpoC1 alleles in Arabidopsis and identified significant differential plasticity under elevated temperatures. Finally, enhanced clock plasticity of de novo ENU (N-Ethyl-N-nitrosourea) -induced barley rpoB1 mutant further implicates the PEP complex as a key player in regulating the circadian clock output. Overall, this study highlights the contribution of specific cytonuclear interaction between rpoC1 (PEP gene) and SIG-B with distinct circadian timing regulation under heat, and their pleiotropic effects on growth implicate an adaptive value.

The role of subsurface instabilities for increasing chlorophyll concentrations in a warming southern Indian ocean

A warming climate is expected to intensify the stratification of the upper ocean in tropical and subtropical regions, which in turn results in decreases in the primary productivity for these oligotrophic areas. To assess if there is trended change in primary productivity in the southern Indian Ocean (IO) with known striking temperature increase, we use 17-years of satellite chlorophyll (Chl) data and model output to examine the trended changes in Chl. The results exhibited a surprisingly increase in Chl concentrations in part of the southern IO over the gyre area. To investigate the potential mechanisms underlying this Chl increase, we used temperature/salinity observations to re-evaluate stratification in the southern IO. The southern IO experienced basin-wide surface warming over the time series however there was a region of subsurface cooling at 50–100 m around 10°S. In the subtropical IO gyre, subsurface warming occurs at faster rates compare to the surface. Through the calculation of buoyancy frequency (N2), we have confirmed the presence of subsurface instabilities caused by these inhomogeneous trends in the vertical thermohaline structure. This was particularly true over the southern IO gyre, which experienced sustained increase of surface mixing disturbances over the last decade—resulting in a more favorable environment for vertical transport of nutrients into the euphotic zone. A mixed layer nutrient budget analysis suggested that entrainment due to mixed layer deepening is crucial in delivering nutrients into the gyre's upper mixed layer, which fueled phytoplankton activity. This emphasizes the importance of considering subsurface instabilities when interpreting the factors that influence surface Chl variabilities. This study highlights the importance of a three-dimensional framework for examining stratification to assess future marine ecosystem responses to a changing climate.

Comparative Proteomics Analysis of Primulina serrulata Leaves Reveals New Insight into the Formation of White Veins

Primulina serrulata is a valuable ornamental herb with rosette leaves and vibrant flowers. Some leaves of this species exhibit a bright and distinct white color along the upper veins, enhancing their ornamental value, while others are less white or entirely green. This variation is observed in adult leaves from natural habitats and among young leaves from seedlings grown in the laboratory. TMT-labeled proteomics technology was used to study the protein-level biogenesis of white-veined (WV) P. serrulata leaves. Our objective was to offer novel insight into the breeding of WV plants. Chlorophyll (Chl) content was significantly lower in the WV group than in the control group. Out of 6261 proteins identified, a mere 69 met the criteria for differentially expressed proteins (DEPs) after stringent screening for subsequent analyses. Among these DEPs, there were 44 proteins that exhibited downregulation and 25 that were upregulated in the WV plants. Some DEPs associated with chloroplasts and Chl biosynthesis were downregulated, leading to the absence of green coloration. Concurrently, Gene Ontology enrichment analysis further emphasized an insufficiency of magnesium, the key element in Chl biosynthesis. Many DEPs associated with abiotic or biotic stressors were downregulated, suggesting an overall weakening of stress resistance with certain compensatory mechanisms. Similarly, many DEPs related to modifying biomacromolecules were downregulated, possibly affected by the decrease in proteins involved in photosynthesis and stress resistance. Some DEPs containing iron were upregulated, indicating that iron is mainly used to synthesize heme and ferritin rather than Chl. Additionally, several DEPs related to sulfur or sulfate were upregulated, suggesting strengthened respiration. Expansin-A4 and pectinesterase were upregulated, coinciding with the emergence of a rough and bright surface in the white area of leaves, indicative of the elongation and gelation processes in the cell walls. These findings provide new insight for future studies to explore the mechanism of color formation in WV leaves.

Physiological Analysis of Source-Sink Relationship in Rice Genotypes with Contrasting Grain Yields.

Rice is a major staple food, and, hence, doubling its productivity is critical to sustain future food security. Improving photosynthesis, source-sink relationships and grain-filling mechanisms are promising traits for improvement in grain yield. To understand the source-sink relationship and grain yield, a set of contrasting rice genotypes differing in yield and biomass were studied for physiological, biochemical and gene-expression differences. The physiological and yield component traits of selected rice genotypes were analyzed in 2016 and 2017 under field conditions. This led to the categorization of genotypes as high yielding (HY) and high biomass, viz., Dular, Gontra Bidhan 3, Way Rarem, Patchai Perumal, Sahbhagi Dhan, Indira Barani Dhan-1, MTU1010, and Maudamani; while, low yielding (LY) and low biomass, viz. Anjali, Ghanteswari, Parijat, Khao Daw Tai, RKVY-104, Ghati Kamma Nangarhar, BAM4510 and BAM5850. The HY genotypes in general had relatively better values of yield component traits, higher photosynthetic rate (Pn) and chlorophyll (Chl) content. The study revealed that leaf area per plant and whole plant photosynthesis are the key traits contributing to high biomass production. We selected two good-performing (Sahbhagi Dhan and Maudamani) and two poor-performing (Ghanteswari and Parijat) rice genotypes for a detailed expression analysis of selected genes involved in photosynthesis, sucrose synthesis, transport, and starch synthesis in the leaf and starch metabolism in grain. Some of the HY genotypes had a relatively high level of expression of key photosynthesis genes, such as RbcS, RCA, FBPase, and ZEP over LY genotypes. This study suggests that traits, such as leaf area, photosynthesis and grain number, contribute to high grain yield in rice. These good-performing genotypes can be used as a donor in a breeding program aimed at high yields in rice.

Shading and Planting Material Type Effects on Some Physiological and Biochemical Compounds Synthesis in Desmodium adscendens Plants Leaves in the Domestication Phase, Daloa, Côte d'Ivoire

Desmodium adscendens (Sw.) is a plant of the Fabaceae Family, a wild medicinal plant frequently found in industrial plantations, where it is exposed to pesticide residues. This makes species unsuitable for use as a raw material in pharmaceutical industry. To this end, domestication is one of best ways of cleaning up the species. During this process, the evaluation of a few physiological and biochemical compounds would be an indicator for the choice of planting material and the ecology species. Two types of plant material (seeds and stem) grown under three types of shade (accentuated, moderate, no shade) were tested. The leaves of various 90-day-old plants were used to determine physiological and biochemical parameters various. Results showed that chlorophyll a, carotenoids, polyphenols, total sugars, protein, proline and the activities of tyrosine ammonia-lyase, polyphenol oxidase and catalase were higher in leaves with moderate and no shading. However, under heavy shading, chlorophyll b content, phenylalanine ammonia lyase (PAL) and peroxidase enzyme activities were higher. Whatever shading type, the chl (a) content remained lower than that of chl (b). Also, total sugars, proline, ascorbate peroxidase and catalase were more abundant in the leaves of plants grown from stem. In contrast, phenolics, proteins and PPO are more abundant in leaves of seedlings.

Effect of Pruning Treatment on Growth Characteristics and Metabolites in Eucommia ulmoides Oliver (E. ulmoides)

The effect of pruning treatments on growth, photosynthesis characteristics, and metabolites were was studied in Eucommia ulmoides Oliver (E. ulmoides). The experiment was carried out from March–August 2019. Three treatments were used: non-pruned trees (CK), a height of 20 cm above the top edge of the flowerpot (T1), and a height of 10 cm above the top edge of the flowerpot (T2). The results showed that the branches branch number, leaves leaf number, and stem diameter increased significantly (p &lt; 0.05) in pruning treatments compared with CK. Similarly, the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum photosynthetic efficiency (Fv/Fm), and non-photochemical quenching coefficient (NPQ) increased significantly in pruning treatments (p &lt; 0.05). Interestingly, the contents of Chl a, Chl b, Chl, Car, and the rate between the Chl a content and the Chl b content increased significantly (p &lt; 0.05) in T2, respectively. These verified that it was a better way to enhance the plants growth of E. ulmoides for pruning treatments. The GC-MS analysis showed that 36 different primary metabolites were identified, including 11 sugars, 13 acids, 5 alcohols, and 7 other compounds, the relative content of their metabolites were was higher in the T2 treatment than that in the T1 treatment, which was mainly concentrated in four main enrichment pathways (Galactose metabolism; Citrate cycle; Glyoxylate and dicarboxylate metabolism; and starch and sucrose metabolism) via KEGG analysis. Meanwhile, correlation analysis showed there were was a positive correlation between the accumulation of D-Galactose, D-Mannose, Succinic acid, and photosynthetic pigment content, and the rate of photosynthesis in T2 treatment (p &lt; 0.05). The pruning height above the top edge of the flowerpot changed the accumulation of primary metabolites and promoted plant regeneration ability in E. ulmoides. Finally, the yield of main secondary metabolites from leaves (Genipin, Geniposide, Geniposidic acid, and Pinoresinol diglucoside) were was increased in pruning treatments by UPLC analysis. It provided a reference for the directional ecological cultivation of E. ulmoides.

Characterization of stress indicators in Tilia cordata Mill. as early and long-term stress markers for water availability and trace element contamination in urban environments

In the context of current climate change, municipalities tend to plant more trees in order to benefit from services they provide in urban areas, such as reducing heat islands. However, in cities, trees are subject to severe abiotic constraints, the main ones being soil contamination and the lack of water due to soil compaction and droughts. This can negatively impact the ecological services provided by trees. Our study aims to help managers in monitoring the phytosanitary status of trees in order to be able to react promptly. In a controlled condition experiment, different plant compounds were analyzed (proline, malondialdehyde-MDA, photosynthetic pigments) in the leaves of young linden trees conventionally grown for planting by the City of Paris, France. They were grown on a trace element (TE) contamination soil gradient, and under different water regimes (well-hydrated/no water stress (Ct), dehydration (Dh), rehydration (Rh)) to see if tested compounds could be early stress markers in trees. Chlorophylls (Chl) could be considered as water and TE-mediated stress markers. Indeed Chl a and b concentrations significantly decreased with dehydration (e.g. respectively −34 % and −24 %) and increasing lead concentration in leaves (respectively, correlation coefficients were −1.08; −0.64 (p < 0.001)). On the contrary, Chl concentrations increased with increasing copper concentration in optimal physiological ranges (correlation coefficients for Chla and Chb were respectively 1.3 and 1.08 (p < 0.05)). Proline and malondialdehyde seemed to be good complementary markers of water stress in the Tilia genus. Indeed, proline concentration increased during the dehydration period (early water stress marker) (mean concentration for Ct, Dh and Rh trees were respectively 3.6, 29.6 and 51.3 µmol.g−1 DW), while MDA increased during the rehydration process (marker for stress accumulation over time) (mean concentration for Ct, Dh, and Rh were respectively 461.8, 313.9 and 493.5 nmol.g−1 DW). In order to reinforce the diagnoses of urban tree managers, these stress indicators should be tested in situ.

Comparative Physiology and Transcriptome Analysis Provides Insights into the Regulatory Mechanism of Albinotic Bambusa oldhamii.

Albinism is a unique problem encountered in tissue culture experiments, but the underlying mechanism remains unclear in most bamboo species. In this study, we identified the putative regulatory genes in an albino mutant of Bambusa oldhamii using comparative physiology and transcriptome analysis. The degeneration of chloroplasts, low chlorophyll (Chl) content and reduced photosynthetic capacity were observed in albinotic B. oldhamii compared to normal lines. A total of 6191 unigenes were identified that were clearly differentially expressed between albino and normal lines by transcriptome sequencing. Most genes related to chloroplast development (such as Psa, Psb) and pigment biosynthesis (such as LHC, GUN4, ZEP) were downregulated significantly in albinotic lines, which might be responsible for the albino phenotype. Moreover, some transcription factors (TFs) such as PIF and GLK1 were identified to be involved in chloroplast development and Chl synthesis, indicating the involvement of putative regulatory pathways PIF-LHC and GLK1-LHC/Psa/Psb in albinotic B. oldhamii. Finally, the downregulation of some stress responsive TFs (like ICE1 and EREB1) suggested a reduction in stress resistance of albinotic B. oldhamii. The above findings provided new insights into the molecular mechanism of albinism in bamboo.

Physiological, Photosynthetic, and Transcriptomics Insights into the Influence of Shading on Leafy Sweet Potato.

Leafy sweet potato is a new type of sweet potato, whose leaves and stems are used as green vegetables. However, sweet potato tips can be affected by pre-harvest factors, especially the intensity of light. At present, intercropping, greenhouse planting, and photovoltaic agriculture have become common planting modes for sweet potato. Likewise, they can also cause insufficient light conditions or even low light stress. This research aimed to evaluate the influence of four different shading levels (no shading, 30%, 50%, and 70% shading degree) on the growth profile of sweet potato leaves. The net photosynthetic rate, chlorophyll pigments, carbohydrates, and polyphenol components were determined. Our findings displayed that shading reduced the content of the soluble sugar, starch, and sucrose of leaves, as well as the yield and Pn. The concentrations of Chl a, Chl b, and total Chl were increased and the Chl a/b ratio was decreased for the more efficient interception and absorption of light under shading conditions. In addition, 30% and 50% shading increased the total phenolic, total flavonoids, and chlorogenic acid. Transcriptome analysis indicated that genes related to the antioxidant, secondary metabolism of phenols and flavonoids, photosynthesis, and MAPK signaling pathway were altered in response to shading stresses. We concluded that 30% shading induced a high expression of antioxidant genes, while genes related to the secondary metabolism of phenols and flavonoids were upregulated by 50% shading. And the MAPK signaling pathway was modulated under 70% shading, and most stress-related genes were downregulated. Moreover, the genes involved in photosynthesis, such as chloroplast development, introns splicing, and Chlorophyll synthesis, were upregulated as shading levels increased. This research provides a new theoretical basis for understanding the tolerance and adaptation mechanism of leafy sweet potato in low light environments.

Natural variation in STAYGREEN contributes to low-temperature tolerance in cucumber.

Low-temperature (LT) stress threatens cucumber production globally; however, the molecular mechanisms underlying LT tolerance in cucumber remain largely unknown. Here, using a genome-wide association study (GWAS), we found a naturally occurring single nucleotide polymorphism (SNP) in the STAYGREEN (CsSGR) coding region at the gLTT5.1 locus associated with LT tolerance. Knockout mutants of CsSGR generated by clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 exhibit enhanced LT tolerance, in particularly, increased chlorophyll (Chl) content and reduced reactive oxygen species (ROS) accumulation in response to LT. Moreover, the C-repeat Binding Factor 1 (CsCBF1) transcription factor can directly activate the expression of CsSGR. We demonstrate that the LT-sensitive haplotype CsSGRHapA , but not the LT-tolerant haplotype CsSGRHapG could interact with NON-YELLOW COLORING 1 (CsNYC1) to mediate Chl degradation. Geographic distribution of the CsSGR haplotypes indicated that the CsSGRHapG was selected in cucumber accessions from high latitudes, potentially contributing to LT tolerance during cucumber cold-adaptation in these regions. CsSGR mutants also showed enhanced tolerance to salinity, water deficit, and Pseudoperonospora cubensis, thus CsSGR is an elite target gene for breeding cucumber varieties with broad-spectrum stress tolerance. Collectively, our findings provide new insights into LT tolerance and will ultimately facilitate cucumber molecular breeding.

In vitro selection of drought-tolerant white poplar clones based on antioxidant activities and osmoprotectant content.

In light of upcoming climate change, there is an urgent requirement for tree improvement regarding adaptability to drought-caused stress and the development of quick and reliable screening methodologies for genotypes' drought tolerance. White poplar is, despite its high adaptability, considered to be an endangered tree species in Serbia, which gives it special importance in the preservation and improvement of biodiversity of riparian ecosystems. The main goal of this research was to evaluate the tolerance of five white poplar clones to the presence of polyethylene glycol (PEG 6000 molecular weight 6000) (different concentrations (e.g. 0 g/L, 1 g/L, 10 g/L, 20 g/L, and 50 g/L) in Aspen Culture Medium (ACM). The tolerance of the clones was evaluated by using morphological parameters (shoot fresh and dry weight, root fresh and dry weight), photosynthetic pigments (contents of chlorophyll a, chlorophyll b, carotenoids, and chlorophyll a+b), and biochemical parameters (total phenolic content, total flavonoid content, ferric reducing antioxidant power, antioxidant activities (DPPH activity and ABTS assay), free proline content and glycine betaine content. The values of morphological and photosynthetic pigments declined with an increase in the concentration of PEG 6000. At a concentration of 50 g/L, the content of shoot fresh mass decreased by 41%, the content of Chl a by 68%, Chl b by 65%, and Car by 76% compared to the control. Also, at the same medium, there was an increase in the content of total phenols, accumulation of proline, the content of glycine betaine as well as in antioxidant activity. Based on the obtained results, it can be assumed that more drought-tolerant clones are characterized by high values for biomass, high content of photosynthetic pigments, and high content of proline and glycine betaine in conditions similar to drought in vitro. Clone L-80 showed better results in most of the tested parameters, especially compared to the reference clone Villafranca.

Non-Destructive Assessment of Leaf Chlorophyll and Epidermal Flavonoids in Two Tomato Cultivars (Solanum lycopersicum L.) Grown Under Different Trichoderma Spp. Treatments

Summary The purpose of this study is to examine the effects of different Trichoderma spp. treatments (T1: Trichoderma harzianum, T2: Trichoderma brevicompactum, and T3: T1 + T2) on two tomato cultivars (‘Narvik’ and ‘Gružanski zlatni’) by the non-destructive monitoring of chlorophyll (Chl) and epidermal flavonol (Flav) indices and nitrogen balance index (NBI) in their leaves. The main objectives were to compare the responses of tomato cultivars considered (grown in a greenhouse) to different Trichoderma strains and a combination of Trichoderma strains. Variations in the Chl, Flav, and NBI values obtained were significantly influenced by nearly all the factors examined (namely the tomato cultivar, experimental week, and treatment), the interaction of which was found significant for all the parameters analyzed. The results obtained indicate that the combinations of strains in the T3 treatment markedly enhanced the Chl content in the ‘Narvik’ cultivar in some experimental weeks. Moreover, reduced NBI values were determined in the Trichoderma-treated ‘Narvik’ plants due to the increased flavonol content, which indicates a shift from primary to secondary metabolism. Further research, including the same cultivars and treatments, is warranted under field conditions to evaluate the physiological responses of the ‘Narvik’ and ‘Gružanski zlatni’ tomato cultivars in a multiple-stressor environment.

Estimating Chlorophyll Content, Production, and Quality of Sugar Beet under Various Nitrogen Levels Using Machine Learning Models and Novel Spectral Indices

Accurately estimating crop performance under various fertilizer levels in a rapid and non-destructive manner has become a vital aspect of precision agriculture technology for both economic and environmental benefits. This study aimed to estimate different sugar beet parameters, such as total chlorophyll (Chlt), chlorophyll a (Chla), chlorophyll b (Chlb), root yield (RY), sugar yield (SY), and sugar content (SC) under five nitrogen (N) levels (0, 30, 60, 90, and 120 kg N ha−1). This was achieved by using a combination of the gradient boosting regression (GBR) model with published and newly developed two- and three-band spectral indices (2D- and 3D-SRIs). The results showed that the N levels had the highest proportion of variations (80.4–92.9%) for all parameters, except for SC, which had more variation (59.9%) according to year than the N levels (37.2%). All parameters, except SC, showed a significant increase with gradually increasing N levels. Additionally, the N levels displayed linear and strong positive relationships with the chlorophyll parameters, and linear and strong negative relationships with SC, while these relationships were quadratic and strong with RY and SY. Several published and novel 3D-SRIs exhibited moderate to strong relationships (R2 = 0.65–0.89) with all parameters. The newly developed 3D-SRIs, which involve wavelengths from the visible, near-infrared, and red-edge regions, such as NDI536, 538, 534, NDI738, 750, 542, and NDI448, 734, 398, were effective in accurately estimating all parameters. Combining 2D-SRIs, 3D-SRIs, and the aggregate of all spectral indices (ASRIs) with GBR models could be a robust strategy for estimating the six observed parameters with reasonable precision. The GBR-ASF-6 SRIs and the GBR-ASF-7 SRIs models performed better in predicting Chl content and SC with R2 values of 0.99 and 0.99 (RMSE = 0.073 and 1.568) for the training dataset and R2 values of 0.65 and 0.78 (RMSE = 0.354 and 6.294) for the testing datasets, respectively. The obtained results concluded that published and newly developed 3D-SRIs, GBR based on 2D-SRIs or 3D-SRIs, and the aggregate of all ASRIs can be used in practice to accurately estimate the Chl content, production, and quality of sugar beet across a wide range of N levels under semiarid conditions.