Phytohormone Content Research Articles

Physiological Properties of Perennial Rice Regenerating Cultivation in Two Years with Four Harvests.

Crop perennialization has garnered global attention recently due to its role in sustainable agriculture. However, there is still a lack of detailed information regarding perennial rice's regenerative characteristics and physiological mechanisms in crop ratooning systems with different rice stubble heights. In addition, the response of phytohormones to varying stubble heights and how this response influences the regenerative characteristics of ratoon rice remains poorly documented. Here, we explored the regenerative characteristics and physiological mechanisms of an annual hybrid rice, AR2640, and a perennial rice, PR25, subjected to different stubble heights (5, 10, and 15 cm). The response of phytohormones to varying stubble heights and how this response influences the regenerative characteristics of ratoon rice were also investigated. The results show that PR25 overwintered successfully and produced the highest yield, especially in the second ratoon season, mainly due to its extended growth duration, higher number of mother stems, tillers at the basal nodes, higher number of effective panicles, and heavier grain weight when subjected to lower stubble heights. Further analysis revealed that PR25 exhibited a higher regeneration rate from the lower-position nodes in the stem with lower stubble heights. this was primarily due to the higher contents of phytohormones, especially auxin (IAA) and gibberellin (GA3) at an early stage and abscisic acid (ABA) at a later stage after harvesting of the main crop. Our findings reveal how ratoon rice enhances performance based on different stubble heights, which provides valuable insights and serves as crucial references for delving deeper into cultivating high-yielding perennial rice.

Bio-inoculation with Serratia CP-13 enhances Cd detoxification via modulation of phytohormone, gas exchange attributes and nutrient acquisition in maize cultivars cultivated in Cd-stressed soil

Heavy metals contamination of soil is increasing rapidly due to prompt in urbanization and industrialization. Recently, cadmium (Cd) pollution has emerged as a severe menace to plant and human health, while the use of plant growth promoting rhizobacteria (PGPR) has appeared as an economical approach for bioremediation of Cd toxicity in crop plants. In this study, the effect of Serratia sp. CP-13 inoculation on two maize cultivars in pre-Cd (0, 5, 12, 18, 26, 30 µM) spiked soil was evaluated. The combined effect of soil Cd and CP-13 application was assessed through the analysis of seed germination, plant biomass, phytohormones, gas exchange attributes, antioxidant production, plant Cd, and nutrient uptake in two (Sahiwal-2002, MMRI-Yellow) maize cultivars. Our outcomes exposed that single treatment of Cd-spiked soil significantly downregulates seed germination, plant biomass, plant nutrients, photosynthetic pigments, indole acetic acid (IAA), total protein, proline, total soluble sugar (TSS), stomatal conductance, transpiration rate, net photosynthesis, and antioxidant production, together with upregulating malondialdehyde (MDA), relative membrane permeability (RMP), abscisic acid (ABA), and Cd uptake in maize cultivars. However, this response of the maize crop against Cd-spiked soil was found to be maximal in Sahiwal-2002 at 30 µM Cd. Furthermore, the inoculation of Cd-resistant CP-13 significantly upregulates the plant accumulation of biomass, seed germination, antioxidants, IAA, gas exchange attributes, photosynthetic pigments, plant physiology, and nutrient uptake and downregulates the MDA, RMP, ABA, and root/shoot Cd accretion in two cultivars of maize. Moreover, this CP-13 based upregulation of plant growth was found to be cultivar (Sahiwal-2002) and Cd treatment (30 µM) specific by controlling the accumulation of lipid peroxidation, phytohormone content, and Cd detoxification. Further, our results indicate that the CP-13 might be a promising and cost effective future biofertilizer for bioremediation of soil Cd.

Peculiarities of soybean-rhizobial systems subject to different levels of water supply fol-lowing treatment with succinic acid and epibrassinolide

All around the world, one of the leading – according to area of cultivated fields – oleic crops is soybean, which has a high demand for moisture. Given the significance of this crop and negative impact of drought on its yield, integrated research of the influence of insufficient water supply on the intensity of physiological-biochemical processes in those plants is necessary for identifying and understanding the drought-tolerance mechanisms of soybean, as well as symbiotic systems created with its participation, and also for search for ways to adapt it to this stressor. Therefore, our objective was determining the specifics of formation and functioning of the symbiotic systems of soybean and Bradyrhizobium japonicum, following treatment with succinic acid (0.01 g/L) and 24-epibrassinolide (0.00001 g/L), subject to different levels of watering. Our studies revealed that pre-sowing treatment of the seeds with a solution of 24-epibrassinolide with their subsequent inoculation with B. japonicum Т21-2 resulted in the most pronounced stimulation of formation and functioning of the symbiotic systems of soybean in the optimal growing conditions. At the same time, during water shortage, the intensity of nitrogen fixation was the highest in the plants grown from seeds that had been successively treated with the acid and the inoculant. We confirmed that water deficit led to significant increase in the overall content of phytohormones of cytokinin nature in the soybean root nodules, depending on the way the seeds were treated. However, the largest pool of cytokinins was seen in the plants that had been treated with succinic acid against the background of both optimal and insufficient water supply. Treatment of the seeds with 24-epibrassinolide caused significant excess of content of zeatin riboside over the content of zeatin during the flowering stage, whereas in the stage of pods formation it led to an opposite effect – excess of zeatin over zeatin riboside. Fourteen days-long water deficit decreased the content of chlorophylls in the leaves and grain productivity of the plants of all variants of the experiment. The use of growth regulators managed to alleviate the negative impact of stress and protect the pigment complex from ruination. Treatment of the seeds with solutions of succinic acid and 24-epibrassinolide provided the growth of soybean grain productivity regardless on water-supply level. The most efficient was 24-epibrassinolide. Therefore, use of 24-epibrassinolide for pre-sowing treatment of the soybean seeds provided formation of effective symbiotic systems with high nitrogen-fixing activity and caused a number of specific changes in the pattern of accumulation of free and complex forms of cytokinins in the root nodules of those plants. At the same time, the treatment provided the highest concentration of photosynthesis pigments in the soybean leaves, and as a result produced the greatest increase in grain productivity of plants of all the variants, regardless of levels of water supply. In turn, use of succinic acid produced the highest level of nitrogen-fixing activity in the case of the lowest number of root nodules in the conditions of insufficient water supply, and also caused significant accumulation of cytokinins in the nodules, compared with other studied variants against the background of both optimal and insufficient water supply. Therefore, it did result in increase in soybean grain productivity, but this was lower than in the plants treated with 24-epibrassinolide.

Enhancing petunia tissue culture efficiency with machine learning: A pathway to improved callogenesis.

The important feature of petunia in tissue culture is its unpredictable and genotype-dependent callogenesis, posing challenges for efficient regeneration and biotechnology applications. To address this issue, machine learning (ML) can be considered a powerful tool to analyze callogenesis data, extract key parameters, and predict optimal conditions for petunia callogenesis, facilitating more controlled and productive tissue culture processes. The study aimed to develop a predictive model for callogenesis in petunia using ML algorithms and to optimize the concentrations of phytohormones to enhance callus formation rate (CFR) and callus fresh weight (CFW). The inputs for the model were BAP, KIN, IBA, and NAA, while the outputs were CFR and CFW. Three ML algorithms, namely MLP, RBF, and GRNN, were compared, and the results revealed that GRNN (R2≥83) outperformed MLP and RBF in terms of accuracy. Furthermore, a sensitivity analysis was conducted to determine the relative importance of the four phytohormones. IBA exhibited the highest importance, followed by NAA, BAP, and KIN. Leveraging the superior performance of the GRNN model, a genetic algorithm (GA) was integrated to optimize the concentration of phytohormones for maximizing CFR and CFW. The genetic algorithm identified an optimized combination of phytohormones consisting of 1.31 mg/L BAP, 1.02 mg/L KIN, 1.44 mg/L NAA, and 1.70 mg/L IBA, resulting in 95.83% CFR. To validate the reliability of the predicted results, optimized combinations of phytohormones were tested in a laboratory experiment. The results of the validation experiment indicated no significant difference between the experimental and optimized results obtained through the GA. This study presents a novel approach combining ML, sensitivity analysis, and GA for modeling and predicting callogenesis in petunia. The findings offer valuable insights into the optimization of phytohormone concentrations, facilitating improved callus formation and potential applications in plant tissue culture and genetic engineering.

Effect of postharvest management on the microbial quality of potato (Solanum tuberosum L.) tubers

Abstract This experiment was conducted to appraise the role of the curing phytohormone treatment and storage method in the postharvest microbial decay of ware potatoes during storage. The study was designed as a Split-Split-Plot Design (SSPD) in which the curing period was placed in the main plot, and the storage method and the phytohormone were put in subplot and sub-sub-plot respectively. Each treatment was replicated three times to form a 4 × 3 × 3 factorial experiment. Each treatment consisted of 20 potato tubers out of which decayed samples were counted for the calculation of percentage rot loss and identification of the causal agent, which was done fortnightly until the end of the storage period of 12 weeks. Temperature, relative humidity, and wind velocity were monitored weekly. All data collected were subjected to analysis of variance (ANOVA) using the GenStat Discovery Edition statistical software package. Means that exhibited significant difference were separated using Duncan’s Multiple Range Test (DMTR) at p = 0.05 level of significance. The results of the analysis showed that the phytohormone levels had highly significant influence (p ≤ 0.01) on percentage rot loss. Although there was a significant interaction between the curing periods and phytohormone concentration, storage conditions (p ≤ 0.05) were observed throughout the storage period of 2–8 weeks. Fusarium solani, Rhizopus oryzae, and Aspergillus niger were implicated in the rotting of potato tubers.

Comparative Transcriptome Analysis between Resistant and Susceptible Pakchoi Cultivars in Response to Downy Mildew.

Downy mildew caused by the obligate parasite Hyaloperonospora brassicae is a devastating disease for Brassica species. Infection of Hyaloperonospora brassicae often leads to yellow spots on leaves, which significantly impacts quality and yield of pakchoi. In the present study, we conducted a comparative transcriptome between the resistant and susceptible pakchoi cultivars in response to Hyaloperonospora brassicae infection. A total of 1073 disease-resistance-related differentially expressed genes were identified using a Venn diagram. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that these genes were mainly involved in plant-pathogen interaction, plant hormone signal transduction, and other photosynthesis-related metabolic processes. Analysis of the phytohormone content revealed that salicylic acid increased significantly in the resistant material after inoculation with Hyaloperonospora brassicae, whereas the contents of jasmonic acid, abscisic acid, and 1-aminocyclopropane-1-carboxylic acid decreased. Exogenous salicylic acid treatment also significantly upregulated Hyaloperonospora brassicae-induced genes, which further confirmed a crucial role of salicylic acid during pakchoi defense against Hyaloperonospora brassicae. Based on these findings, we suggest that the salicylic-acid-mediated signal transduction contributes to the resistance of pakchoi to downy mildew, and PAL1, ICS1, NPR1, PR1, PR5, WRKY70, WRKY33, CML43, CNGC9, and CDPK15 were involved in this responsive process. Our findings evidently contribute to revealing the molecular mechanism of pakchoi defense against Hyaloperonospora brassicae.

ZmDRR206 functions in maintaining cell wall integrity during maize seedling growth and defense response to external stresses

Plants adaptively change their cell wall composition and structure during their growth, development, and interactions with environmental stresses. Dirigent proteins (DIRs) contribute to environmental adaptations by dynamically reorganizing the cell wall and/or by generating defense compounds. A maize DIR, ZmDRR206, was previously reported to play a dominant role in regulation of storage nutrient accumulation in endosperm during maize kernel development. Here we show that ZmDRR206 mediates maize seedling growth and disease resistance by coordinately regulating biosynthesis of cell wall components for cell-wall integrity (CWI) maintenance. Expression of ZmDRR206 was induced in maize seedlings upon pathogen infection. ZmDRR206 overexpression in maize resulted in reduced seedling growth and photosynthetic activity but increased disease resistance and drought tolerance, revealing a tradeoff between growth and defense. Consistently, ZmDRR206 overexpression reduced the contents of primary metabolites and down-regulated genes involved in photosynthesis, while increasing the contents of major cell wall components, defense phytohormones, and defense metabolites, and up-regulated genes involved in defense and cell-wall biosynthesis in seedlings. ZmDRR206-overexpressing seedlings were resistant to cell-wall stress imposed by isoxaben, and ZmDRR206 physically interacted with ZmCesA10, which is a cellulose synthase unit. Our findings suggest a mechanism by which ZmDRR206 coordinately regulates biosynthesis of cell-wall components for CWI maintenance during maize seedling growth, and might be exploited for breeding strong disease resistance in maize.

Influence of Exogenous 24-Epicasterone on the Hormonal Status of Soybean Plants.

Brassinosteroids (BRs) are key phytohormones involved in the regulation of major processes of cell metabolism that guide plant growth. In the past decades, new evidence has made it clear that BRs also play a key role in the orchestration of plant responses to many abiotic and biotic stresses. In the present work, we analyzed the impact of foliar treatment with 24-epicastasterone (ECS) on the endogenous content of major phytohormones (auxins, salicylic acid, jasmonic acid, and abscisic acid) and their intermediates in soybean leaves 7 days following the treatment. Changes in the endogenous content of phytohormones have been identified and quantified by LC/MS. The obtained results point to a clear role of ECS in the upregulation of auxin content (indole-3-acetic acid, IAA) and downregulation of salicylic, jasmonic, and abscisic acid levels. These data confirm that under optimal conditions, ECS in tested concentrations of 0.25 µM and 1 µM might promote growth in soybeans by inducing auxin contents. Benzoic acid (a precursor of salicylic acid (SA)), but not SA itself, has also been highly accumulated under ECS treatment, which indicates an activation of the adaptation strategies of cell metabolism to possible environmental challenges.

Perfluoroalkyl substances exposure alters stomatal opening and xylem hydraulics in willow plants

Climate change and pollution are increasingly important stress factors for life on Earth. Dispersal of poly- and perfluoroalkyl substances (PFAS) are causing worldwide contamination of soils and water tables. PFAS are partially hydrophobic and can easily bioaccumulate in living organisms, causing metabolic alterations. Different plant species can uptake large amounts of PFAS, but little is known about its consequences for the plant water relation and other physiological processes, especially in woody plants. In this study, we investigated the fractionation of PFAS bioaccumulation from roots to leaves and its effects on the conductive elements of willow plants. Additionally, we focused on the stomal opening and the phytohormonal content. For this purpose, willow cuttings were exposed to a mixture of 11 PFAS compounds and the uptake was evaluated by LC-MS/MS. Stomatal conductance was measured and the xylem vulnerability to air embolism was tested and further, the abscisic acid and salicylic acid contents were quantified using LC-MS/MS. PFAS accumulated from roots to leaves based on their chemical structure. PFAS-exposed plants showed reduced stomatal conductance, while no differences were observed in abscisic acid and salicylic acid contents. Interestingly, PFAS exposure caused a higher vulnerability to drought-induced xylem embolism in treated plants. Our study provides novel information about the PFAS effects on the xylem hydraulics, suggesting that the plant water balance may be affected by PFAS exposure. In this perspective, drought events may be more stressful for PFAS-exposed plants, thus reducing their potential for phytoremediation.

Inconsistent phenotypic differentiation at physiological traits in Norway spruce (Picea abies Karst.) provenances under contrasting water regimes

Abstract Norway spruce is expected to suffer from drought stress and other manifestations of climate change. This study relies on a manipulative experiment with drought-stressed and well-watered (control) seedlings, comprising five provenances of Norway spruce distributed along a steep elevational transect from 550 to 1,280 m a.s.l. within the natural range. Seedlings were subjected to measurement of physiological traits (content of phytohormones and monoterpenes, slow and fast chlorophyll a fluorescence kinetics, gas exchange, hyperspectral indices), and genotyping at 8 nuclear microsatellite loci. Comparison of the coefficient of differentiation at neutral loci (FST ) vs. differentiation at phenotypic traits (PST ) was used to identify traits underlying divergent selection. In total, 18 traits exhibited a significant PST – FST difference. However, the consistency in differentiation patterns between drought-stressed and control plants was limited, only three traits exhibited signals of selection under both treatments. This outcome indicates that the identified differentiation patterns can only be interpreted in the context of environmental setup of the experiment, and highlights the importance of common gardens in adaptation research, as they allow both elimination of environment-induced phenotypic variation and studying genotype-by-environment interaction in physiological responses to environmental stresses.

Tomato growth and physiology as well as soil physicochemical and biological properties affected by ozonated water in a saline agroecosystem

Current trends in agriculture are focused on implementing sustainable practices that avoid the use of chemical compounds. It is important to propose environmentally friendly methods, which may enhance plant growth physiology and yield without affecting soil microbial community as much. In this context, irrigation with ozonated water could be a potential strategy to reduce some chemical compounds in soils due to the degradative power of ozone. Here, we studied the impact of irrigation with ozonated water on the microbial community of a Mediterranean soil, and on Solanum lycopersicum L. agro-physiology and productivity in a greenhouse experiment. To this end, we evaluated: i) soil physicochemical properties, soil enzyme activities, microbial biomass via fatty acid analysis, microbial diversity (via amplicon sequencing), and ii) the nutrient content, physiology, phytohormone content, yield, and fruit quality of tomato plants. Our results indicate that soil physicochemical properties were significantly affected by the irrigation with ozonated water (OZ). We observed an increase in the content of total organic carbon (TOC), water-soluble nitrogen (WSN) and ammonium, and a decrease in soil pH due to the OZ treatment. In addition, a significant increase in alkaline phosphatase and fungal and bacterial biomass was also observed in the OZ treatment. It was observed that the prokaryotic community structure was affected by the OZ treatment, while that of fungi was undisturbed. The OZ treatment increased the photosynthetic rates of tomato plants and maintained water conditions when compared to control plants. The increased trans-Zeatin riboside (tZ-Rib) could provide rapid apical and root growth allowing adaptation to the new growing conditions. However, a more in-depth study on the physiological response of the plant to this treatment would be of interest, as it would help with the implementation of this strategy in agricultural fields in a safe manner, and with obtaining higher plant yields.

Putrescine, in Combination with Gibberellic Acid and Salicylic Acid, Improves Date Palm Fruit Quality via Triggering Protein and Carbohydrate Accumulation and Enhancing Mineral, Amino Acid, Sugar, and Phytohormone Acquisition

AbstractPutrescine (Put), gibberellic acid (GA3), and salicylic acid (SA) are involved in improving fruit growth and development. This is the first study investigating the effect of 1 mM Put, 100 mg L-1 GA3, and 100 mg L-1 SA on Phoenix dactylifera, cv. Zaghloul fruits. The experiment was conducted in a completely randomized block design during two successive seasons and five treatments [control (distilled water spray), Put, Put + GA3, Put + SA, and Put + GA3 + SA] were sprayed at the Hababouk (cell division) stage and Kimri [unripe green (cell elongation)] stage. Our results showed that all treatments significantly improved the yield and quality of ‘Zaghloul’ fruit by increasing the dry matter, crude fiber, ash, total soluble solids, (reducing, non-reducing, and total soluble) sugars, carbohydrate, protein, nitrogen, phosphorus, potassium, calcium, magnesium, sodium, zinc, iron, and manganese content as well as the peroxidase and catalase activity. Compared with the control treatment, exogenous applications also enhanced the amino acid (glutamic acid, aspartic acid, proline, glycine, alanine, arginine, cysteine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tyrosine, valine) acquisition and phytohormone (indole-3-acetic acid, cytokinins, GA3, SA) content, while decreasing the percentage of moisture, total acidity, total phenols, and tannins. The novel evidence indicates that among all treatments, application of diamine (Put), in combination with phytohormones (GA3 and SA), has the greatest effect on improving ‘Zaghloul’ fruit yield by up-regulating the nutrient acquisition, sugar accumulation, amino acid profile, antioxidant response, and phytohormone performance. These findings support the use of Put in conjunction with GA3 and SA to improve fruit yield and quality.

Collectible Cell Lines of Larix sibirica Obtained by Somatic Embryogenesis and Their Ability to Regenerate

A protocol for the cultivation of Larix sibirica Ledeb. by somatic embryogenesis was developed (RF Patent No. 2456344, 2012). The L. sibirica collection consisted of 22 actively proliferating cell lines (CLs) obtained from immature zygotic embryos. The age of CLs ranged from 1 to 14 years. CLs differed in their growth intensity, embryonic productivity, hormonal balance, and genetic stability, as well as in their regenerative ability. In most proliferating CLs, the formation of globular somatic embryos continued for 2–4 years. Here, a number of CLs actively proliferated for 9–14 years or more. The formation of embryogenic cultures in L. sibirica is associated with the content of phytohormones and their localization in embryo cells. The cytogenetic studies revealed the genetic stability of young CLs (up to 1 year), in which the karyotype consisted of the diploid number of chromosomes (2n = 24). Genomic mutations were observed in the long-term proliferation of CLs. Individual CLs can maintain cytogenetic stability for many years; such CLs can successfully be used to preserve germplasm, obtain planting material, and for plantation reforestation.

Gibberellic Acid and Salicylic Acid Dual Application Improves Date Palm Fruit Growth by Regulating the Nutrient Acquisition, Amino Acid Profile, and Phytohormone Performance

Gibberellic acid (GA3) and salicylic acid (SA) are crucial phytohormones that support fruit development. The objective of this study was to investigate the mechanism of spraying 100 mg L−1 GA3 and 100 mg L−1 SA in improving the Phoenix dactylifera, cv. Zaghloul fruit yield and quality. The experiment was conducted in a randomized complete block design during two successive growing seasons and four treatments [control (distilled water spray), 100 mg L−1 GA3, 100 mg L−1 SA, and 100 mg L−1 GA3 + 100 mg L−1 SA] were sprayed at the Hababouk and Kimri stages of date palm “Zaghloul” cv. The findings revealed that the GA3 and/or SA applications are necessary for improving the growth and development of “Zaghloul” fruit, which were associated with an increase in the content of dry matter, crude fiber, ash, total soluble solids, total soluble sugars, carbohydrate, protein, and essential nutrients. Moreover, compared with the control treatment, GA3 and/or SA exogenous treatments improved the activity of peroxidase and catalase, as well as the content of amino acids and phytohormones, while decreasing the content of moisture, total acidity, total phenol, and tannins. The results provide evidence that using GA3 in conjunction with SA has the greatest effect on improving “Zaghloul” fruit yield by up regulating the sugar accumulation, amino acid profile, nutrient acquisition, antioxidant capacity, and phytohormone performance. Consequently, combining GA3 with SA can be an effective strategy for enhancing fruit yield and quality.

Phosphorus Acquisition Efficiency and Transcriptomic Changes in Maize Plants Treated with Two Lignohumates.

Lignohumates are increasing in popularity in agriculture, but their chemistry and effects on plants vary based on the source and processing. The present study evaluated the ability of two humates (H1 and H2) to boost maize plant performance under different phosphorus (P) availability (25 and 250 μM) conditions in hydroponics, while understanding the underlying mechanisms. Humates differed in chemical composition, as revealed via elemental analysis, phenol and phytohormone content, and thermal and spectroscopic analyses. H1 outperformed H2 in triggering plant responses to low phosphorus by enhancing phosphatase and phytase enzymes, P acquisition efficiency, and biomass production. It contained higher levels of endogenous auxins, cytokinins, and abscisic acid, likely acting together to stimulate plant growth. H1 also improved the plant antioxidant capacity, thus potentially increasing plant resilience to external stresses. Both humates increased the nitrogen (N) content and acted as biostimulants for P and N acquisition. Consistent with the physiological and biochemical data, H1 upregulated genes involved in growth, hormone signaling and defense in all plants, and in P recycling particularly under low-P conditions. In conclusion, H1 showed promising potential for effective plant growth and nutrient utilization, especially in low-P plants, involving hormonal modulation, antioxidant enhancement, the stimulation of P uptake and P-recycling mechanisms.

Enhancing sustainability through microalgae cultivation in urban wastewater for biostimulant production and nutrient recovery

Microalgae can produce biostimulants in form of phytohormones, which are compounds that, even if applied in low concentrations, can have stimulant effects on plants growth and can enhance their quality and their resistance to stress. Considering that microalgal biomass can grow recovering nutrients from wastewater, this circular approach allows to use residues for the production of high added value compounds (such as phytohormones) at low cost. The interest on biostimulants production from microalgae have recently raised. Scientists are focused on the direct application of these cellular extracts on plants, while the number of studies on the identification of bioactive molecules, such as phytohormones, is very scarce. Two cyanobacteria strains (Synechocystis sp. (SY) and Phormidium sp. (PH)) and a chlorophyte (Scenedesmus sp. (SC)) were cultured in laboratory-scale PBRs with a working volume of 2.5 L in secondary urban wastewater varying N:P ratio in the cultures to obtain the highest productivity. The variation of N:P ratio affects microalgae growth, and SY and PH presented higher productivities (73 and 48 mg L−1 d, respectively) under higher N:P ratio (> 22:1). Microalgal biomass was freeze-dried and phytohormones content was measured with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The three microalgae showed similar phytohormones profiles, being the auxin (indole-3-acetic acid, IAA) the most abundant (72 ng g−1DW in SY). Proteins were major macronutrient for all strains, reaching 48 %DW in PH culture. To optimize the biostimulants production, a balance between the production of such compounds, biomass productivity and nutrients removal should be taken into consideration. In this sense, SC was the most promising strain, showing the highest N and P removal rates (73 % and 59 %, respectively) while producing phytohormones.

An arbuscular mycorrhizal fungus differentially regulates root traits and cadmium uptake in two maize varieties

Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi that colonize plant roots, and they are more common in Cd-polluted habitats. However, there is limited understanding of the response of root traits and cadmium (Cd) uptake to AMF in different crop varieties. Two maize varieties, Panyu 3 and Ludan 8, with high and low Cd uptake capacities, respectively, were cultivated as host plants in a pot experiment with Cd-polluted soil (17.1 mg/kg Cd). The effects of AMF on the growth, mineral nutrient concentration, root traits, phytohormone concentrations and Cd uptake of the two maize varieties and their comprehensive response to AMF fungal inoculation were investigated. AMF improved growth, mineral nutrient levels and root morphology and increased lignin and phytohormone concentrations in roots and Cd uptake in the two maize varieties. However, the two maize varieties, Panyu 3 and Ludan 8, had different responses to AMF, and their comprehensive response indices were 753.6% and 389.4%, respectively. The root biomass, branch number, abscisic acid concentrations, lignin concentrations and Cd uptake of maize Panyu 3 increased by 151.1%, 28.6%, 139.7%, 99.5% and 84.7%, respectively. The root biomass, average diameter, auxin concentration, lignin concentration and Cd uptake of maize Ludan 8 increased by 168.7%, 31.8%, 31.4%, 41.7% and 136.7%, respectively. Moreover, Cd uptake in roots presented very significant positive correlations with the average root diameter and abscisic acid concentration. A structural equation model indicated that the root abscisic acid concentration and root surface area had positive effects on Cd uptake by the Panyu 3 maize roots; the root abscisic acid concentration and root tip number had positive effects on Cd uptake by the Ludan 8 maize roots. Thus, AMF differentially regulated Cd uptake in the two maize varieties, and the regulatory effect was closely related to root traits and phytohormone concentrations.

Hormonal involvement in boosting the vegetative vigour underlying caffeine-related improvements in lentil production

Previous studies have shown that caffeine (1,3,7-trimethylxanthine) has some potential for its use as a biostimulant ingredient for boosting lentil production at suboptimal temperatures. However, some limitations to its use include its potential side effects as an emerging contaminant and the current lack of knowledge of its mechanism of action. Here, we aimed to study the mechanisms underlying improved lentil production upon caffeine application. Greenhouse-grown plants treated with caffeine (at 10-5 M, 10-4 M, and 10-3 M) were compared to an untreated, control treatment, and both reproductive and vegetative vigour were evaluated in parallel with endogenous foliar concentrations of phytohormones, including both stress and growth-related hormones. Results showed an enhanced lentil production at the highest caffeine concentration (10-3 M) which might be attributed, at least in part, to a greater vegetative vigour. The hormonal profiling revealed a dual effect. Firstly, there was a specific increase in jasmonoyl-isoleucine (JA-Ile) in the short term, which may provide a priming effect. Secondly, abscisic acid (ABA) content kept at low levels and the active cytokinin (CK) isopentenyl adenine (2-iP) increased and persisted at high levels throughout the reproductive stage. Cytokinin-mediated effects on growth, and more specifically the high CK/ABA ratios in leaves, appeared to mediate caffeine-related effects in boosting vegetative vigour. In conclusion, caffeine emerges as a compelling alkaloid for integration into biostimulant formulations due to its favorable effect in boosting lentil production through an improvement of vegetative vigour. These outcomes appear to be modulated by phytohormones, most notably jasmonates, priming plants for improved performance under suboptimal temperatures, and cytokinins, alongside ABA and its associated ratios, collectively enhancing plant growth and reproductive vigour in challenging conditions.

<i>rol</i>-Genes of Agrobacteria: Possible Biological Functions

As a result of agrobacterium-mediated transformation the rolA, rolB, rolC, and rolD genes of Agrobacterium rhizogenes are integrated into plant genomes as part of T-DNA. These genes cause abundant growth of hairy roots, and the regeneration of shoots from them causes short stature, shortening of internodes and wrinkled leaves. A sufficient number of representatives of the genera Nicotiana, Linaria, Ipomoea and others in their genome contain some rol genes that got into them during horizontal gene transfer and thus evolutionarily fixed. The conservatism of the rol genes of A. rhizogenes in naturally transgenic plants can probably be associated with the performance of important biological functions by them. The purpose of this review article is to review the currently available data on the biological role of rol genes in hairy roots, transformed plants, and naturally transgenic plants. The results of scientific studies published to date describe the expression of rol genes both together and separately. It should be noted that expression has a different effect on the morphology of both plants transformed by agrobacteria and naturally transgenic species. The review presents the results of studies that have shown a positive effect of rol genes on secondary metabolism, the antioxidant system and plant stress resistance. The question of the possible effect of protein products of rol genes through the influence on the content of phytohormones or sensitivity to them is also discussed. Experimental evidence of subcellular localization of Rol proteins and enzymatic activity of Rol proteins with respect to phytohormone glucosides are described. However, these experiments did not give exhaustive answers, and therefore studies of the biological functions of the rol genes should be continued. This knowledge can be used to create transgenic and genome-edited plants that have economically valuable traits.

Combined Effect of PGPR Strains <i>Pseudomonas plecoglossicidA</i> 2,4-D and Humic Substances on the Growth, Content of Photosynthetic Pigments and Phytohormones in Wheat Plants in Drought Conditions

The aim of the study was to study the effect of bacteria that stimulate plant growth and humic substances on the content of chlorophyll, nitrogen balance index, cytokinin concentration, abscisic acid in wheat plants grown in drought conditions. The accumulation of the raw mass of wheat plants during treatment with a strain of Pseudomonas plecoglossicida 2,4-D bacteria and humic substances with a deficiency of soil moisture is shown. Stimulation of plant growth is associated with the activation of root growth, which led to an increase in the nitrogen balance index and chlorophyll concentration in the treated plants. The detected increase in the concentration of chlorophyll in plants treated with P. plecoglossicida 2,4-D correlated with a decrease in the content of abscisic acid in shoots, and in plants treated with humates – with an increase in cytokinins in shoots. A higher efficiency of plant treatment with a combination of bacteria and humic substances than any of them individually may be associated with the additive effect of these treatments on hormonal balance.