Phytohormone Content Research Articles

Optimization of Selected Minerals and a Cytokinin for In Vitro Propagation of Little-Leaf Mockorange (Philadelphus microphyllus A. Gray) Using Response Surface Methodology (RSM).

Optimizing concentrations of minerals and phytohormones is essential when culturing a new plant species. The objective of this study was to use Response Surface Methodology (RSM) to evaluate combinations of selected minerals (N, Ca, and P) along with zeatin (Zea) to obtain optimum shoot growth of little-leaf mockorange. Forty-six treatment combinations were assigned using Proc Optex in SAS software version 9.4. The concentrations of Zea tested were 0.82, 1.095, or 1.37 µM, and the minerals were 22.5, 30, or 37.5 mM N, 1.13, 1.5, or 1.875 mM Ca, and 0.31, 0.625, or 0.937 mM P. Treatment concentrations were tested for their effects on the number of axillary shoots formed, shoot length, and dry weight. The response surface analyses showed that the optimum concentrations of N, Ca, and P were 34 to 39 mM, 1.5 mM, and 0.625 mM, respectively. Medium supplemented with 1.1 µM Zea affected shoot growth positively. Comparison of mineral concentrations in medium with concentrations in full-strength Murashige and Skoog (MS) medium, suggests ½ MS medium should be appropriate to efficiently multiply little-leaf mockorange shoots efficiently, thus saving the time and money involved in creating a custom medium formulation.

Effect of Rhizospheric Bacteria Capable of Biosynthesis and/or Destruction of Phytohormones on the Growth Characteristics and Hormonal Status of Wheat Plants in Conditions of Water Scarcity

The ability of various strains of soil bacteria to synthesize and/or destroy plant growth regulators: indolyl-3-acetic acid (IAA), cytokinins (CK) and abscisic acid (ABA) has been shown. Bacteria stimulated the growth of shoots and roots of soft wheat under normal conditions of moisture and drought, had a significant effect on the content of phytohormones in shoots and roots of plants. The most promising growth stimulators were strains with an average level of IAA production in combination with the ability to destroy phytohormones: Pseudomonas protegens DA1.2, P. plecoglossicida 2.4-D and the cytokinin-producing strain P. chlororaphis IB-6.

In vitro propagation, synthetic seeds production and clonal fidelity assessment of regenerants of endangered herb Rheum emodi

Rheum emodi, pharmaceutically important medicinal plant is mainly found in northern Himalayas. This herb has therapeutic properties such as anticancerous, antimicrobial, behaves like astringent and improves gastro related problems. All these factors contribute in immense decline of this herb in its natural habitat as it is excessively used by local people for medicinal as well as common eating purpose. We have optimized the efficient in vitro plant regeneration system through the callus from leaf explant and synthetic seed production for this herb. The culture medium used was Murashige and Skoog (MS) basal medium with the different concentration of phytohormones. Highest percentage of callus formation (84.44±0.27%) was observed in MS medium perforated with 2,4-D in combination with BAP. The maximum number of shoots (3.67±0.27) per explant was attained on MS medium with BAP (35.5 μM) and Kn (11.61 μM). For synthetic seed production, encapsulation was done in 3% of sodium alginate+ 50mM CaCl2. The highest survival and germination frequency of somatic embryos without storage period were observed as 78.9±1.33 and 66.7±0.58 respectively. The survival and germination rate of encapsulated embryos at 4 ͦC were significantly reduced as compared to non-stored somatic embryos. For ascertaining the clonal fidelity, 20 ISSR markers and 15 RAPD markers were assayed and employed to validate the true-to-type regenerants of Rheum emodi. Out of 15 RAPD and 20 ISSR markers, 7 markers and 15 markers produced distinct, clear and scorable bands. All the markers produced the monomorphic bands and no variation was detected among the micropropagated plants. Thus, the analysis of ISSR and RAPD patterns revealed that the bands were shared by both the in vitro raised plants and parent clump confirming the genetic stability. These markers proved to be a model tool for routine analysis of clonal fidelity of micropropagated plants prior to commercialization. These protocols could be beneficial in the future for rapid and mass multiplication or propagation of Rheum emodi and dissemination of synthetic or artificial seeds.

Machine learning-based prediction models unleash the enhanced production of fucoxanthin in Isochrysis galbana.

The marine microalga Isochrysis galbana is prolific producer of fucoxanthin, which is a xanthophyll carotenoid with substantial global market value boasting extensive applications in the food, nutraceutical, pharmaceutical, and cosmetic industries. This study presented a novel integrated experimental approach coupled with machine learning (ML) models to predict the fucoxanthin content in I. galbana by altering the type and concentration of phytohormone supplementation, thus overcoming the multiple methodological limitations of conventional fucoxanthin quantification. A novel integrated experimental approach was developed, analyzing the effect of varying phytohormone types and concentrations on fucoxanthin production in I. galbana. Morphological analysis was conducted to assess changes in microalgal structure, while growth rate and fucoxanthin yield correlations were explored using statistical analysis and machine learning models. Several ML models were employed to predict fucoxanthin content, with and without hormone descriptors as variables. The findings revealed that the Random Forest (RF) model was highly significant with a high of 0.809 and of 0.776 when hormone descriptors were excluded, and the inclusion of hormone descriptors further improved prediction accuracy to of 0.839, making it a useful tool for predicting the fucoxanthin yield. The model that fitted the experimental data indicated methyl jasmonate (0.2 mg/L) as an effective phytohormone. The combined experimental and ML approach demonstrated rapid, reliable, and cost-efficient prediction of fucoxanthin yield. This study highlights the potential of machine learning models, particularly Random Forest, to optimize parameters influencing microalgal growth and fucoxanthin production. This approach offers a more efficient alternative to conventional methods, providing valuable insights into improving fucoxanthin production in microalgal cultivation. The findings suggest that leveraging diverse ML models can enhance the predictability and efficiency of fucoxanthin production, making it a promising tool for industrial applications.

Carotenoid-carbohydrate crosstalk: evidence for genetic and physiological interactions in storage tissues across crop species.

Carotenoids play essential roles in photosynthesis, photoprotection, and human health. Efforts to increase carotenoid content in several staple crops have been successful through both conventional selection and genetic engineering methods. Interestingly, in some cases, altering carotenoid content has had unexpected effects on other aspects of plant metabolism, impacting traits like sugar content, dry matter percentage, fatty acid content, stress tolerance, and phytohormone concentrations. Studies across several diverse crop species have identified negative correlations between carotenoid and starch contents, as well as positive correlations between carotenoids and soluble sugars. Collectively, these reports suggest a metabolic interaction between carotenoids and carbohydrates. We synthesize evidence pointing to four hypothesized mechanisms: (1) direct competition for precursors; (2) physical interactions in plastids; (3) influences of sugar or apocarotenoid signaling networks; and (4) nonmechanistic population or statistical sources of correlations. Though the carotenoid biosynthesis pathway is well understood, the regulation and interactions of carotenoids, especially in nonphotosynthetic tissues, remain unclear. This topic represents an underexplored interplay between primary and secondary metabolism where further research is needed.

Phytohormonal balance and differential gene expression in chronically irradiated Scots pine populations from the chernobyl affected zone.

The impact of chronic radiation exposure on phytohormone content and expression of phytohormone- and stress-related genes of Scots pine in the zone affected by the Chernobyl accident was studied. Needle samples were collected from three plots with contrasting levels of radioactive contamination in the Polesye State Radiation-Ecological Reserve, Republic of Belarus, and two reference plots in the Kozeluzhsky forest in June 2022. The experimental plots were located within the artificial plantations of Scots pine established in 1982, before the accident in 1986. The activity of radionuclides 137Cs, 90Sr, 241Am, 238Pu, and 239+240Pu in soil and needles ensured dose rates ranging from 3.3 to 87 mGy × year-1, while at the reference plots, the range was 0.7‒0.8 mGy × year-1. Concentrations of plant hormones, including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), zeatin, and abscisic acid (ABA) in needles were evaluated using high-performance liquid chromatography (HPLC). We demonstrate that chronic radiation exposure is a significant stress factor that affects both phytohormonal balance and the expression of some important phytohormone- and stress-related genes. We found a tendency toward decreased ABA and auxin concentrations in trees from plots contaminated with radionuclides. The ratio (IAA + IBA + zeatin)/ABA was drastically raised at the most contaminated plots Masany and Kulazhin, reflecting the functional rearrangements of cellular metabolism that ensure plant adaptation under chronic radiation exposure. Changes in gene expression indicated modulation of ABA and Ca2+ signalling pathways, decreased potential of zeatin biosynthesis, and activation of heat shock proteins biosynthesis.

Polyacrylamide Regulated Phytohormone Balance and Starch Degradation to Promote Seed-Potato Sprouting and Emergence

Potatoes are typically seeded as tubers, and their slow sprouting significantly impacts production. Therefore, the effects of polyacrylamide (20 g·L−1, 30 g·L−1, and 40 g·L−1) as a seed potato dressing on sprouting, seedling growth, and biomass were investigated. The phytohormone content, respiratory intensity, and starch metabolism enzyme activity were analyzed to elucidate the physiological mechanisms involved. The sprouting rate significantly increased after 20 g·L−1 and 30 g·L−1 treatments by 40.63% and 15.63%, respectively. The sprouting energy was the highest (52.0%) at 20 g·L−1, 7.67 times higher than the control. The 20 g·L−1 and 30 g·L−1 treatments also promoted emergence and growth, with the emergence rate increasing by 18.18% and 27.27% and growth increasing by over 8.1% and 11.9%, respectively. These effects were related to changes in phytohormone content and accelerated starch conversion. After treatment, the auxin and cytokinin contents in the apical buds increased significantly at the germination initiation stage, and during the germination and vigorous growth phases, the auxin, cytokinin, and gibberellin contents increased. Polyacrylamide treatment activated α-amylase and promoted starch degradation, increasing soluble sugar content to provide nutrients and energy for sprouting. This study provides a promising approach for promoting potato tuber sprouting and seedling growth.

Hormonal determination of rhizogenesis in Shrub rose regenerants cultivated in vitro

The study of the reproduction characteristics of roses of the garden class Shrub, the definition of the dependence of the hormonal determination of explant rhizogenesis on the concentrations of phytohormones that are part of the nutrient media, is relevant and has both scientific and practical interest. The article presents the results of studies of hormonal determination of rhizogenesis in explants of cultivars of roses of the garden class Shrub: ‘Gärtnerfreude’ (W. Kordes’ Söhne, 1991), ‘Lavender Dream’ (G. P. Ilsink, 1984), ‘Pomponella’ (W. Kordes’ Söhne, 2005), ‘Red Cascade’ (R. S. Moore, 1976), ‘Sommerabend’ (W. Kordes’ Söhne, 1995) cultivated in vitro on nutrient media containing growth regulators. It has been established that of the nutrient media modified by the addition of 0.2–1.0 mg/l α-naphthylacetic acid (α-NAA), the most effective was the medium with the content of α-NAA 0.5 mg/l, the content of macro- and microelements half of the Murashige and Skoog prescriptions, and a decrease in the sucrose content to 2.0%. On this medium, the frequency of rhizogenesis averaged 61.2% for the studied cultivars. Hormonal determination of rhizogenesis and efficiency of root formation in vitro in the Shrub rose regenerants depended on the genotype of the plant (the cultivar): cv. ‘Gärtnerfreude’ (61.0%) and cv. ‘Lavender Dream’ (66.0%) had the highest rhizogenesis ability. The use of the universal growth regulator “Humifield” in combination with 0.5 mg/l α-NAA contributed to an increase in the rooting rate of the studied rose cultivars up to 70.0–86.0%.

Chemical activation of biochar derived from coffee husk for the adsorption of phytohormones from waste coconut water

Abstract The potential of NaOH-activated biochar derived from waste coffee husks via pyrolysis for the extraction of phytohormones from waste coconut water was investigated. The raw coffee husk biochar (CHB) and coffee husk activated biochar (CHAB) were characterized and compared in terms of morphology, particle size distribution, elemental composition, surface functional groups, bulk density, phytohormone adsorption efficiency and equilibrium adsorption capacity. The phytohormone adsorption efficiency of the CHB and CHAB produced were 62.36% and 91.33%, respectively. Future work includes flask adsorption experiments and using the phytohormone content extracted from the coconut water for tissue culture studies. Collectively, results from this study present an alternative use of coconut and coffee wastes, and ultimately contribute to the waste management processes of the coconut and coffee industries.

Transcriptomic and coexpression network analyses revealed the regulatory mechanism of Cydia pomonella infestation on the synthesis of phytohormones in walnut husks

The codling moth (Cydia pomonella) has a major effect on the quality and yield of walnut fruit. Plant defences respond to insect infestation by activating hormonal signalling and the flavonoid biosynthetic pathway. However, little is known about the role of walnut husk hormones and flavonoid biosynthesis in response to C. pomonella infestation. The phytohormone content assay revealed that the contents of salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), jasmonic acid-isoleucine conjugate (JA-ILE), jasmonic acid-valine (JA-Val) and methyl jasmonate (MeJA) increased after feeding at different time points (0, 12, 24, 36, 48, and 72 h) of walnut husk. RNA-seq analysis of walnut husks following C. pomonella feeding revealed a temporal pattern in differentially expressed genes (DEGs), with the number increasing from 3,988 at 12 h to 5,929 at 72 h postfeeding compared with the control at 0 h postfeeding. Walnut husks exhibited significant upregulation of genes involved in various defence pathways, including flavonoid biosynthesis (PAL, CYP73A, 4CL, CHS, CHI, F3H, ANS, and LAR), SA (PAL), ABA (ZEP and ABA2), and JA (AOS, AOC, OPR, JAZ, and MYC2) pathways. Three gene coexpression networks that had a significant positive association with these hormonal changes were constructed based on the basis of weighted gene coexpression network analysis (WGCNA). We identified several hub transcription factors, including the turquoise module (AIL6, MYB4, PRE6, WRKY71, WRKY31, ERF003, and WRKY75), the green module (bHLH79, PCL1, APRR5, ABI5, and ILR3), and the magenta module (ERF27, bHLH35, bHLH18, TIFY5A, WRKY31, and MYB44). Taken together, these findings provide useful genetic resources for exploring the defence response mediated by phytohormones in walnut husks.

The Diterpene Isopimaric Acid Modulates the Phytohormone Pathway to Promote Oryza sativa L. Rice Seedling Growth.

Many plant secondary metabolites are active and important in the regulation of plant growth. Certain plant-derived diterpenes are known to promote plant growth, but the pathways by which this promotion occurs are still unknown. Activity screening revealed that the plant-derived diterpene isopimaric acid exhibits growth-promoting activity in rice (Oryza sativa L.) seedlings. Furthermore, 25 μg/mL of isopimaric acid promoted the growth of 15 self-incompatible associated populations from different rice lineages to different extents. Quantitative analyses revealed a significant decrease in the concentration of the defense-related phytohormone abscisic acid (ABA) following treatment with isopimaric acid. Correlation analysis of the phytohormone concentrations with growth characteristics revealed that the length of seedling shoots was significantly negatively correlated with concentrations of 3-indole-butyric acid (IBA). Moreover, the total root weight was not only negatively correlated with ABA concentrations but also negatively correlated with concentrations of isopentenyl adenine (iP). These data suggest that isopimaric acid is able to influence the phytohormone pathway to balance energy allocation between growth and defense in rice seedlings and also alter the correlation between the concentrations of phytohormones and traits such as shoot and root length and weight. We provide a theoretical basis for the development and utilization of isopimaric acid as a plant growth regulator for rice.

Field evaluation and characterization of a novel biostimulant for broccoli (Brassica oleracea var. italica) cultivation under drought and salt stress which increases antioxidant, glucosinolate and phytohormone content

Anthropogenic global warming is affecting crop yield and thus compromising food security. Drought and salinization of the irrigation water or soil are increasingly frequent in most arable land, specifically in arid and semiarid areas such as the Mediterranean basin. Many crops have been displaced or their yield has plummeted in recent years, causing food shortages and price increases. In a context of global population growth and reduction in the availability of natural resources used in agriculture, finding novel tools that help farmers to maintain yield in an increasingly arid and saline scenario is of pivotal importance. This is particularly important in organic agriculture, where the number of available tools is very limited. Biostimulants are substances or microorganisms of natural origin whose function is to stimulate plant processes related to nutrient absorption, nutrient use efficiency, tolerance to abiotic stress or the quality of the agricultural products obtained. In the present work, we have evaluated, in field, the agronomic effectiveness of a novel biostimulant formulation in a cruciferous crop of great interest in the Mediterranean basin (broccoli) under control conditions, water and salt stress. Our research has shown that our product had a positive effect on broccoli production and in delaying flowering time. We have also found that the application of our biostimulant increased enzymatic and non-enzymatic antioxidant defense under drought conditions. Similarly, when exposed to salinity, the biostimulant increased the concentration of different phytohormones and glucosinolates. Taken together, our biostimulant increases the tolerance of broccoli to salt stress and water limitation by increasing the antioxidant response, the level of glucosinolates and eliciting the hormonal response.

Phytohormone-induced changes in growth, physiology, and biochemistry of Aurantiochytrium sp. for sustainable bioproduction

The study aimed to assess the effects of nine combinations of phytohormones, salicylic acid (SA), gibberellic acid (GA), and jasmonic acid (JA) on the growth, physiology, and biochemistry of Aurantiochytrium sp. Parameters like optical density (OD), biomass, protein content, hydrogen peroxide (H2O2), malondialdehyde (MDA), catalase activity (CAT), and gene expression (malic enzyme (ME) and acetyl-CoA carboxylase (ACCase)) were assessed at various cultivation stages (24, 48, 72, and 96 h). The research also analyzed fatty acid composition, unsaturated fatty acids (UFA), saturated fatty acids (SFA), and the UFA to SFA ratio (USS) to understand the biochemical changes induced by phytohormones. Results demonstrated that modifying phytohormone concentrations significantly affected the characteristics of the microalgae, particularly in correlation with different growth stages, emphasizing the necessity of precise control of phytohormone levels for optimizing cultivation conditions and enhancing bioactive compound production in Aurantiochytrium sp.

The combination of a microbial and a non-microbial biostimulant increases yield in lettuce (Lactuca sativa) under salt stress conditions by up-regulating cytokinin biosynthesis.

Salinization poses a significant challenge in agriculture, exacerbated by anthropogenic global warming. Biostimulants, derived from living microorganisms or natural extracts, have emerged as valuable tools for conventional and organic agriculture. However, our understanding of the molecular mechanisms underlying the effects of biostimulants is very limited, especially in crops under real cultivation conditions. In this study, we adopted an integrative approach to investigate the effectiveness of the combined application of plant growth-promoting bacterium (Bacillus megaterium strain BM08) and a non-microbial biostimulant under control conditions (normal watering) and salt stress. After confirming the yield increase under both conditions, we investigated the molecular mechanisms underlying the observed effect by measuring a number of physiological parameters (i.e., lipid peroxidation, antioxidants, chlorophylls, total phenolics and phytohormone content), as well as RNA sequencing and primary metabolite analyses. Our findings reveal that the combined effect of the microbial and non-microbial biostimulants led to a decrease in the antioxidant response and an up-regulation of genes involved in cytokinin biosynthesis under salt stress conditions. This, in turn, resulted in a higher concentration of the bioactive cytokinin, isopentenyladenosine, in roots and leaves and an increase in γ-aminobutyric acid, a non-proteic amino acid related to abiotic stress responses. In addition, we observed a decrease in malic acid, along with an abscisic acid (ABA)-independent up-regulation of SR-kinases, a family of protein kinases associated with abiotic stress responses. Furthermore, we observed that the single application of the non-microbial biostimulant triggers an ABA-dependent response under salt stress; however, when combined with the microbial biostimulant, it potentiated the mechanisms triggered by the BM08 bacterial strain. This comprehensive investigation shows that the combination of two biostimulants is able to elicit a cytokinin-dependent response that may explain the observed yield increase under salt stress conditions.

The response of Midknight Valencia oranges to ethephon degreening varies in the turning and regreening stages.

Late-ripening citrus plays an important role in the stability of the global citrus industry. However, the regreening phenomenon in Valencia oranges impacts the peel color and commercial value. Ethylene degreening is an effective technique to improve the color of citrus fruits, but this effect may be delayed in regreened oranges. To better clarify this phenomenon, plastid morphology, pigment and phytohormone content in ethephon-degreened Midknight Valencia oranges harvested in different stages were evaluated. Results showed that in fruits harvested at the turning stage, ethephon degreening treatment induced a chloroplast-to-chromoplast transition, and chlorophyll degradation and carotenoid accumulation were accelerated. Conversely, in fruits harvested at the regreening stage, the changes in plastid morphology were minimal, with delayed changes in chlorophyll and carotenoids. Genes related to ethylene biosynthesis and signaling pathways supported these responses. Variations in endogenous auxin, jasmonic acid, abscisic acid and gibberellins could partially explain this phenomenon. The response of Midknight Valencia oranges to ethephon degreening was delayed in the regreening stage, possibly due to the dynamic variations in endogenous phytohormones. © 2024 Society of Chemical Industry.

A delayed response in phytohormone signaling and production contributes to pine susceptibility to Fusarium circinatum

BackgroundFusarium circinatum is the causal agent of pine pitch canker disease, which affects Pinus species worldwide, causing significant economic and ecological losses. In Spain, two Pinus species are most affected by the pathogen; Pinus radiata is highly susceptible, while Pinus pinaster has shown moderate resistance. In F. circinatum-Pinus interactions, phytohormones are known to play a crucial role in plant defense. By comparing species with different degrees of susceptibility, we aimed to elucidate the fundamental mechanisms underlying resistance to the pathogen. For this purpose, we used an integrative approach by combining gene expression and metabolomic phytohormone analyses at 5 and 10 days post inoculation.ResultsGene expression and metabolite phytohormone contents suggested that the moderate resistance of P. pinaster to F. circinatum is determined by the induction of phytohormone signaling and hormone rearrangement beginning at 5 dpi, when symptoms are still not visible. Jasmonic acid was the hormone that showed the greatest increase by 5 dpi, together with the active gibberellic acid 4 and the cytokinin dehydrozeatin; there was also an increase in abscisic acid and salicylic acid by 10 dpi. In contrast, P. radiata hormonal changes were delayed until 10 dpi, when symptoms were already visible; however, this increase was not as high as that in P. pinaster. Indeed, in P. radiata, no differences in jasmonic acid or salicylic acid production were found. Gene expression analysis supported the hormonal data, since the activation of genes related to phytohormone synthesis was observed earlier in P. pinaster than in the susceptible P. radiata.ConclusionsWe determine that the moderate resistance of P. pinaster to F. circinatum is in part a result of early and strong activation of plant phytohormone-based defense responses before symptoms become visible. We suggest that jasmonic acid signaling and production are strongly associated with F. circinatum resistance. In contrast, P. radiata susceptibility was attributed to a delayed response to the fungus at the moment when symptoms were visible. Our results contribute to a better understanding of the phytohormone-based defense mechanism involved in the Pinus-F. circinatum interactions and provide insight into the development of new strategies for disease mitigation.

Integrated analysis of transcriptomics and defense-related phytohormones to discover hub genes conferring maize Gibberella ear rot caused by Fusarium Graminearum

BackgroundGibberella ear rot (GER) is one of the most devastating diseases in maize growing areas, which directly reduces grain yield and quality. However, the underlying defense response of maize to pathogens infection is largely unknown.ResultsTo gain a comprehensive understanding of the defense response in GER resistance, two contrasting inbred lines ‘Nov-82’ and ‘H10’ were used to explore transcriptomic profiles and defense-related phytohormonal alterations during Fusarium graminearum infection. Transcriptomic analysis revealed 4,417 and 4,313 differentially expressed genes (DEGs) from the Nov-82 and H10, respectively, and 647 common DEGs between the two lines. More DEGs were obviously enriched in phenylpropanoid biosynthesis, secondary metabolites biosynthesis, metabolic process and defense-related pathways. In addition, the concentration of the defense-related phytohormones, jasmonates (JAs) and salicylates (SAs), was greatly induced after the pathogen infection. The level of JAs in H10 was more higher than in Nov-82, whereas an opposite pattern for the SA between the both lines. Integrated analysis of the DEGs and the phytohormones revealed five vital modules based on co-expression network analysis according to their correlation. A total of 12 hub genes encoding fatty acid desaturase, subtilisin-like protease, ethylene-responsive transcription factor, 1-aminocyclopropane-1-carboxylate oxidase, and sugar transport protein were captured from the key modules, indicating that these genes might play unique roles in response to pathogen infection,ConclusionsOverall, our results indicate that large number DEGs related to plant disease resistance and different alteration of defensive phytohormones were activated during F. graminearum infection, providing new insight into the defense response against pathogen invasion, in addition to the identified hub genes that can be further investigated for enhancing maize GER resistance.

Advance in the Thermoinhibition of Lettuce (Lactuca sativa L.) Seed Germination.

Thermoinhibition refers to the inability of seeds to germinate when inhibited by high temperatures, but when environmental conditions return to normal, the seeds are able to germinate rapidly again, which is different from thermodormancy. Meanwhile, with global warming, the effect of the thermoinhibition phenomenon on the yield and quality of crops in agricultural production is becoming common. Lettuce, as a horticultural crop sensitive to high temperature, is particularly susceptible to the effects of thermoinhibition, resulting in yield reduction. Therefore, it is crucial to elucidate the intrinsic mechanism of action of thermoinhibition in lettuce seeds. This review mainly outlines several factors affecting thermoinhibition of lettuce seed germination, including endosperm hardening, alteration of endogenous or exogenous phytohormone concentrations, action of photosensitizing pigments, production and inhibition of metabolites, maternal effects, genetic expression, and other physical and chemical factors. Finally, we also discuss the challenges and potential of lettuce seed germination thermoinhibition research. The purpose of this study is to provide theoretical support for future research on lettuce seed germination thermoinhibition, and with the aim of revealing the mechanisms and effects behind lettuce seed thermoinhibition. This will enable the identification of more methods to alleviate seed thermoinhibition or the development of superior heat-tolerant lettuce seeds.

Integrated morphological, physiological and transcriptomic analyses reveal the responses of Toona sinensis seedlings to low-nitrogen stress

Nitrogen is one of the most essential elements for plant growth and development. In this study, the growth, physiology, and transcriptome of Toona sinensis (A. Juss) Roem seedlings were compared between low-nitrogen (LN) and normal-nitrogen (NN) conditions. These results indicate that LN stress adversely influences T. sinensis seedling growth. The activities of key enzymes related to nitrogen assimilation and phytohormone contents were altered by LN stress. A total of 2828 differentially expressed genes (DEGs) in roots and 1547 in leaves were identified between the LN and NN treatments. A differential enrichment analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways indicated that nitrogen and sugar metabolism, flavonoid biosynthesis, plant hormone signal transduction, and ABC transporters, were strongly affected by LN stress. In summary, this research provides information for further understanding the response of T. sinensis to LN stress.

Evaluation of the Content of Steroid Phytohormones in Humic Preparations

Evaluation of the Content of Steroid Phytohormones in Humic Preparations