Promoted Shoot Growth Research Articles

Harnessing plant-beneficial bacterial encapsulation: A sustainable strategy for facilitating cadmium bioaccumulation in Medicago sativa

Plant-beneficial bacteria (PBB) have emerged as a promising approach for assisting phytoremediation of heavy metal (HM)-contaminated soils. However, their colonization efficiency is often challenged by complex soil environments. In this study, we screened one rhizobacterium (Klebsiella variicola Y38) and one endophytic bacterium (Serratia surfactantfaciens Y15) isolated from HM-contaminated soils and plants for their high resistance to Cd and strong growth-promoting abilities. These strains were encapsulated individually or in combination with alginate and applied with Medicago sativa in Cd-contaminated soil pot experiments. The effectiveness of different bacterial formulations in promoting plant growth and enhancing Cd bioconcentration in M. sativa was evaluated. Results showed that PBB application enhanced plant growth and antioxidant capacity while reducing oxidative damage. Encapsulated formulations outperformed unencapsulated ones, with combined formulations yielding superior results to individual applications. Quantitative PCR indicated enhanced PBB colonization in Cd-contaminated soils with alginate encapsulation, potentially explaining the higher efficacy of alginate-encapsulated PBB. Additionally, the bacterial agents modified Cd speciation in soils, resulting in increased Cd bioaccumulation in M. sativa by 217–337 %. The alginate-encapsulated mixed bacterial agent demonstrated optimal effectiveness, increasing the Cd transfer coefficient by 3.2-fold. Structural equation modeling and correlation analysis elucidated that K. variicola Y38 promoted Cd bioaccumulation in M. sativa roots by reducing oxidative damage and enhancing root growth, while S. surfactantfaciens Y15 facilitated Cd translocation to shoots, promoting shoot growth. The combined application of these bacteria leveraged the benefits of both strains. These findings contribute to diversifying strategies for effectively and sustainably remediating Cd-contaminated soils, while laying a foundation for future investigations into bacteria-assisted phytoremediation.

A mature liquid fertilizer derived from cattle urine promotes Arabidopsis thaliana growth via hormone-like responses.

To understand the fertilization effects of liquid fertilizer (LF) produced by aerobic microbial processing of cattle urine, we investigated the influence of LF on growth and shoot genetic responses of the model plant Arabidopsis thaliana. LF significantly enhanced both shoot and root growth under aseptic conditions. Although filtrate from ultrafiltration (molecular weight cutoff: 10000) also promoted shoot growth and root elongation, the concentrate only promoted root growth. Multiple growth-promoting factors were therefore associated with the growth promotion. Transcriptome analysis of shoots following LF addition identified 353 upregulated and 512 downregulated genes. According to gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses, signal transduction of a phytohormone cytokinin was influenced by LF addition. Cytochrome P450 induction triggered the related signal transitions, and would introduce the growth promotion for shoot. Primary auxin responses and abscisic acid signaling responses were also observed in the presence of LF. Ethylene signaling seemed to be insensitive.

Bacterial consortium based on Pseudomonas fluorescens, Lysinibacillus xylanilyticus and Bacillus velezensis reduces clubroot disease in broccoli

Clubroot disease caused by Plasmodiophora brassicae is the most devastating disease in Brassicaceae plants. Control of clubroot is limited because of the survival of resting spores of the pathogen in the soil for years. Crop rotation, liming of the soil, fungicides and resistant cultivars have not been totally efficient in reducing the damages of the disease or pathogen spread. Although biocontrol with microorganisms has shown potential against clubroot, the variable results when using individual strains have made implementation difficult. Thus, the aim of this work was to determine whether a consortium of selected beneficial microorganisms is more efficient in controlling clubroot in broccoli than single strains. Single strains of bacteria from the Lysinibacillus, Bacillus and Pseudomonas genera (5 × 107 cells ml−1) and Trichoderma spp. (1 × 106 conidia ml−1) were evaluated in an initial screening. Four strains showing the best performance on plant growth and reduction of clubroot were evaluated as consortia in a further experiment. Treatments were applied in nursery (4 ml plant−1), and to the soil one week before transplant and the day of transplant (60 ml plant−1 each time). Plant shoot and root dry weight and the incidence and severity of clubroot were recorded. Supernatant from liquid cultures of Pseudomonas migulae Pf014 and Lysinibacillus xylanilyticus Br042, and washed cells of Bacillus velezensis Bs006 and B. pumilus Br019 promoted shoot growth of the plants. Single applications of Trichoderma asperellum Th034, Bs006, Br042 and Pseudomonas fluorescens Ps006 showed biocontrol potential against clubroot. However, the consortia built of Bs006, Br042 and Ps006 showed the highest reduction of clubroot incidence (78%) and severity (74%). A synergistic interaction by this consortium was found compared with the efficacy of single strains. To our knowledge, this work reports for the first time a consortium based on three rhizobacteria with high potential to control clubroot disease.

The impact of sucrose and 6-benzylaminopurine on shoot propagation and vitrification in Aroniamelanocarpa (black chokeberry)

Vitrification is one of the most significant issues encountered in plant tissue culture applications. It diminishes the quality of in vitro plants, causing their leaves and stems to appear watery and translucent, and it may impede the success of the acclimatization step. In this respect, this study investigates the impact of sucrose and 6-Benzylaminopurine (BAP) concentrations on shoot regeneration and vitrification development in Aronia melanocarpa, known for its high antioxidant content and health benefits. Initially, the presence of BAP, in combination with varying sucrose concentrations, leads to a substantial increase in shoot number, and the largest number (7 shoots per nodal explant) was observed in the Murashige and Skoog (MS) medium containing 3% sucrose and 5.0 mg/L BAP. Furthermore, sucrose concentration plays a crucial role in shoot growth, with higher concentrations promoting more extensive shoot development. However, when 3% sucrose was combined with higher BAP (from 1.0- to 5.0 mg/L), an increased incidence of vitrification was observed over time. Interestingly, lower sucrose concentrations (1% or 2%) combined with 0.5 mg/L or 2.5 mg/L BAP initially delayed vitrification but eventually led to its occurrence. Microscopic analysis of leaf samples with varying levels of vitrification indicates significant differences in the density of stomata, further confirming the detrimental impact of vitrification on cellular structures and physiological processes. The recovery of vitrified plants was evaluated using different growth media combinations. The absence of BAP in the medium led to higher recovery percentages (min 96%) without necrosis, while the addition of 0.5 mg/L BAP promoted shoot growth but potentially inhibited root development. It has been found that media with 1 mg/L BAP and either 10 g/L or 20 g/L sucrose, as well as media with 30 g/L sucrose and 0.5 mg/L BAP, are the most suitable for efficient shoot regeneration with minimal vitrification risk. However, increasing BAP levels for faster shoot regeneration also raises the risk of vitrification. During acclimatization, vitrified plants exhibited stunted shoot growth, shorter and narrower leaves, reduced root numbers and lengths, and decreased survival rates, particularly under lower humidity conditions. The cultivation period required for the recovery of the crop was determined to be 6 weeks under greenhouse conditions for a sustainable plant propagation.

Nutrient availability and growth of bell pepper plants under fertilization management with humic substances and cattle manure.

Humic substances associated with cattle manure can enhance and reduce the costs of organic fertilization. In this sense, the objective was to evaluate the application of humic substances in association with cattle manure on soil fertility, growth and root nutrition in pepper plants. The experimental design used was randomized blocks, arranged in a factorial scheme with 4 doses of cattle manure (8, 18, 28 and 38 Mg ha-1), 3 doses of humic substances (0, 8 and 12 kg ha-1), with 4 replicates. The variables analyzed were plant height, stem diameter, leaf area, root growth, fresh and root dry weight, root macronutrient contents and soil fertility. Increases in plant height, leaf area and root dry matter (21.2, 58.21 and 8% respectively) were obtained by associating the application of humic substances with manure. Humic substances (12 kg ha-1) in association with manure (8 Mg ha-1) provided an increase in nitrogen content in the roots (36.05%) compared to the application of manure alone, and the application of humic substances (12 kg ha-1) promoted an increase of 10.62% in potassium content in the roots. The availability of calcium in the soil regulated primary root growth. The association of humic substances with cattle manure promoted shoot growth, root dry weight and root nutritional increase in pepper plants.

5-Amino uracil activated silver nano resonators for highly selective visual detection of dopamine and as an agonist towards BAP: Promoting shoot growth in Bacopa monnieri L.

Silver nanoparticles (AgNPs) with an average size of about 17.5 nm have been synthesized using 5-amino uracil as a reducing and capping agent. The concentration of these AgNPs was worked out to be 48 nM. These AgNPs served as a highly selective optical sensor against an important neurotransmitter like dopamine (DA) at its nano molar level (94 nM) with the linearity range of 1–5 µM. The quantification of DA in one of its injection sample was also achieved with a recovery of 91 %. Studies like FTIR, UV–Vis, XPS, SEM, TEM, EDX, DLS and Zeta potential measurements have supported our findings. Significant amplification in the Raman signal of DA was also observed upon its addition into as prepared AgNPs solution. Moreover, these AgNPs seemed to augment the activity of cytokinin (BAP) in synergistic fashion and enhanced in vitro high frequency shoots regeneration in B. monnieri L. and also led to increment in its antioxidant metabolite contents like phenol and flavonoid.

Simulated global warming affects endophytic bacterial and fungal communities of Antarctic pearlwort leaves and some bacterial isolates support plant growth at low temperatures

Antarctica is one of the most stressful environments for plant life and the Antarctic pearlwort (Colobanthus quitensis) is adapted to the hostile conditions. Plant-associated microorganisms can contribute to plant survival in cold environments, but scarce information is available on the taxonomic structure and functional roles of C. quitensis-associated microbial communities. This study aimed at evaluating the possible impacts of climate warming on the taxonomic structure of C. quitensis endophytes and at investigating the contribution of culturable bacterial endophytes to plant growth at low temperatures. The culture-independent analysis revealed changes in the taxonomic structure of bacterial and fungal communities according to plant growth conditions, such as the collection site and the presence of open-top chambers (OTCs), which can simulate global warming. Plants grown inside OTCs showed lower microbial richness and higher relative abundances of biomarker bacterial genera (Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Aeromicrobium, Aureimonas, Hymenobacter, Novosphingobium, Pedobacter, Pseudomonas and Sphingomonas) and fungal genera (Alternaria, Cistella, and Vishniacozyma) compared to plants collected from open areas (OA), as a possible response to global warming simulated by OTCs. Culturable psychrotolerant bacteria of C. quitensis were able to endophytically colonize tomato seedlings and promote shoot growth at low temperatures, suggesting their potential contribution to plant tolerance to cold conditions.

The Arabidopsis Receptor-like Kinase CAP1 Promotes Shoot Growth under Ammonium Stress.

Simple SummaryUnderstanding the underlying mechanisms of NH4+ toxicity is essential for improving nitrogen use efficiency. Although numerous genes and factors have been identified to function in modulating the response to NH4+ stress, NH4+ toxicity remains poorly characterized. Our work reported here demonstrated a new role for CAP1 in shoot growth in response to NH4+ stress. The enhanced sensitivity of the cap1-1 mutant to NH4+ stress is linked with the role of CAP1 in regulation cell wall loosening and ROS accumulation.High levels of ammonium (NH4+) in soils inhibit plant growth and nitrogen utilization efficiency. Elucidating the underlying mechanisms of NH4+ toxicity is essential for alleviating the growth inhibition caused by high NH4+. Our previous work showed that [Ca2+]cyt-associated protein kinase 1 (CAP1) regulates root hair growth in response to NH4+ in Arabidopsis thaliana, and the cap1-1 mutant produces short root hairs under NH4+ stress conditions. However, it is unclear whether CAP1 functions in other physiological processes in response to NH4+. In the present study, we found that CAP1 also plays a role in attenuating NH4+ toxicity to promote shoot growth. The cap1-1 mutant produced smaller shoots with smaller epidermal cells compared with the wild type in response to NH4+ stress. Disruption of CAP1 enhanced the NH4+-mediated inhibition of the expression of cell enlargement-related genes. The cap1-1 mutant showed elevated reactive oxygen species (ROS) levels under NH4+ stress, as well as increased expression of respiratory burst oxidase homologue genes and decreased expression of catalase genes compared with the wild type. Our data reveal that CAP1 attenuates NH4+-induced shoot growth inhibition by promoting cell wall extensibility and ROS homeostasis, thereby highlighting the role of CAP1 in the NH4+ signal transduction pathway.

Phosphorus acquisition strategies of wheat are related to biochar types added in cadmium-contaminated soil: Evidence from soil zymography and root morphology

Biochar application for the remediation of cadmium (Cd)-contaminated soils may result in a relative deficiency of phosphorus (P) due to the disruption of soil nutrient balance. However, the P acquisition strategies of plants in such situation are still unclear. In this study, analyses on soil zymography and root morphology were combined for the first time to investigate the effects of pristine and P-modified biochars from apple tree branches on the P acquisition strategies of wheat under Cd stress. The results show that the application of pristine biochar exacerbated the soil's relative P deficiency. Wheat was forced to improve foraging for P by forming longer and thinner roots (average diameter 0.284 mm) as well as releasing more phosphatase to promote P mobilization in the soil. Moreover, bioavailable Cd affected the P acquisition strategies of wheat through stimulating the release of phosphatase from roots. The P-modified biochar maintained high levels of Olsen-P (>100 mg kg−1) in the soil over time by slow release, avoiding the creation of relative P deficiency in the soil; and increased the average root diameter (0.338 mm) and growth performance index, which promoted shoot growth (length and biomass). Furthermore, the P-modified biochar reduced DTPA-extracted Cd concentration in soils by 79.8 % (pristine biochar by 26.9 %), and decreased the Cd translocation factor from root to shoot as well as Cd concentration in the shoots. Therefore, P-modified biochar has a great potential to regulate the soil element balance (carbon, nitrogen, and P), promote wheat growth, and remediate the Cd-contaminated soil.

Performance of Taxonomically Diverse Native Isolates of Mycorrhizal Fungi in Symbiosis with Young Grapevines

Grapevines rely on arbuscular mycorrhizal fungi (AMF) to obtain ample phosphorus (P) from soils with low to moderate P like the Ultisols of western Oregon. Prior research indicated that nine species, or virtual taxa, of AMF colonized the roots of ‘Pinot noir’ at greater than 1% abundance in a single vineyard. However, little is known about how different taxa within a community vary in their capacity to function as symbionts with grapevines. The effectiveness of five native AMF species representing five genera to promote growth and nutrient uptake of ‘Pinot noir’ was examined in a fumigated Ultisol soil under well-watered and periodically dry conditions. Plants were grown with each of the different isolates alone or without AMF. After 8 and 16 weeks, whole vines were destructively harvested and biomass and nutrients were determined. Results showed that four of the isolates colonized roots extensively, increased root and shoot biomass, and predominantly increased P uptake. A Claroideoglomus isolate was superior in promoting shoot growth as compared with Rhizophagus irregularis, even though both isolates increased P uptake to the same extent, suggesting a higher carbon cost for R. irregularis. Scutellospora calospora failed to colonize roots beyond a trace and had no impact on vine performance. The ability to increase P uptake among the four effective fungi was not related to the frequency of arbuscules in roots suggesting that some P exchange occurs via hyphae within the cortex, particularly for Funneliformis mosseae. Water limitation reduced P uptake as a main effect across all mycorrhizal treatments, suggesting that the native isolates studied here have similar functionality under well-watered and periodically dry conditions.

Cow Manure Compost Promotes Maize Growth and Ameliorates Soil Quality in Saline-Alkali Soil: Role of Fertilizer Addition Rate and Application Depth

Soil salinization and alkalization is a global problem restricting agricultural production. This study compared different fertilizer regimes (addition rate and application depth) on maize growth and soil quality in saline-alkali soil. Cow manure compost was applied with addition rates of 6, 12, 18 and 24 t·ha−1, and application depths of 5 and 20 cm, along with 0.6 t·ha−1 mineral fertilizer, and compared to a control treatment with only mineral fertilizer application. Results indicated that cow manure compost application could promote maize growth and ameliorate soil quality in saline-alkali soil. Increasing cow manure compost addition rate alleviated soil salinity better than alkalinity, while increasing compost application depth could reduce soil alkalinity more effectively than soil salt content. Moreover, increasing cow manure compost addition rate improved soil organic matter and soil nutrient content, thus promoting shoot growth and maize yield. However, increasing cow manure compost application depth could boost root growth, and further absorbed more nutrients to promote maize yield. Cow manure compost application increased maize yield by 6.0% to 28.4% with a maximum yield of 8.14 t·ha−1 in a treatment with compost addition rate of 24 t·ha−1 and application depth of 20 cm. Comprehensive evolution of soil quality, maize growth and maize yield, cow manure compost addition rate of 24 t·ha−1 and application depth of 20 cm along with 0.6 t·ha−1 mineral fertilizer application is suggested for use in saline-alkali soil.

Killing two birds with a single stone-genetic manipulation of cytokinin oxidase/dehydrogenase (CKX) genes for enhancing crop productivity and amelioration of drought stress response.

The development of high-yielding, bio-fortified, stress-tolerant crop cultivars is the need of the hour in the wake of increasing global food insecurity, abrupt climate change, and continuous shrinking of resources and landmass suitable for agriculture. The cytokinin group of phytohormones positively regulates seed yield by simultaneous regulation of source capacity (leaf senescence) and sink strength (grain number and size). Cytokinins also regulate root-shoot architecture by promoting shoot growth and inhibiting root growth. Cytokinin oxidase/dehydrogenase (CKX) are the only enzymes that catalyze the irreversible degradation of active cytokinins and thus negatively regulate the endogenous cytokinin levels. Genetic manipulation of CKX genes is the key to improve seed yield and root-shoot architecture through direct manipulation of endogenous cytokinin levels. Downregulation of CKX genes expressed in sink tissues such as inflorescence meristem and developing seeds, through reverse genetics approaches such as RNAi and CRISPR/Cas9 resulted in increased yield marked by increased number and size of grains. On the other hand, root-specific expression of CKX genes resulted in decreased endogenous cytokinin levels in roots which in turn resulted in increased root growth indicated by increased root branching, root biomass, and root-shoot biomass ratio. Enhanced root growth provided enhanced tolerance to drought stress and improved micronutrient uptake efficiency. In this review, we have emphasized the role of CKX as a genetic factor determining yield, micronutrient uptake efficiency, and response to drought stress. We have summarised the efforts made to increase crop productivity and drought stress tolerance in different crop species through genetic manipulation of CKX family genes.

Impact of Phytomediated Zinc Oxide Nanoparticles on Growth and Oxidative Stress Response of In Vitro Raised Shoots of Ochradenus arabicus.

Biogenic nanoparticles have potential roles in the growth and development of plants and animals as they are ecofriendly and free of chemical contaminants. In this study, we assessed the effects of phytomediated zinc oxide nanoparticles (ZnONPs) on shoot growth, biochemical markers, and antioxidant system response in Ochradenus arabicus, which is a medicinal plant. The shoot length and fresh and dry weights were found to be higher in groups with 5 and 10 mg/L ZnONPs than in the control. At high concentrations of ZnONPs (50, 100, and 300 mg/L), biomass was decreased in a concentration-dependent manner. The shoot number was observed to be highest at 50 mg/L among all applied concentrations of ZnONPs. The levels of the stress markers proline and TBARS were found to be higher in shoots treated with 100 and 300 mg/L ZnONPs than in the control as well as NP-treated shoots. The levels of antioxidant enzymes were significantly increased at high concentrations of nanoparticles compared with the control. Thus, synthesized phytomediated ZnONPs from shoots of O. arabicus and their application to the same organ of O. arabicus in vitro were found to be effective as a low concentration of nanoparticles promoted shoot growth, resulting in high biomass accumulation. Thus, using green nanotechnology, such endemic plants could be conserved in vitro and multiple shoots could be produced by reducing the phytohormone concentration for multiple uses, such as the production of potential secondary metabolites.

Efecto del sustrato y el ácido naftalenacético en la propagación vegetativa Hypericum brasiliense (Hypericaceae)

Hypericum brasiliense is a medicinal herb that contains chemical compounds, which can be used in medicine as an analgesic, anti-inflammatory and antidepressant. The aim of the present work was to evaluate the influence of substrate type and the addition or absence of naphthaleneacetic acid (NAA) on the rooting of stem cuttings. To carry out the study, 10 cm cuttings were obtained from H. brasiliense plants that were maintained in greenhouses for one year. Fifty percent of these were subjected to hormonal treatments with NAA at a concentration of 100 mg kg-1 for 30 minutes and the rest did not receive this treatment. Subsequently, the cuttings were placed in 50 cm3 containers with the substrates sand, pine bark or perlite and different combinations of these. Sand alone or combined with perlite were the best substrates for inducing adventitious rhizogenesis and promoting shoot growth, and pine bark the least efficient. H. brasiliensis cuttings have a high root development capacity without the addition of NAA, but root development is affected by the type of substrate.

Arbuscular mycorrhizal fungi reverse selenium stress in Zea mays seedlings by improving plant and soil characteristics

Selenium (Se) is a beneficial trace element for certain animals including humans, while remaining controversial for plants. High Se concentration in soil is toxic to plants especially at seedling stage of the plants. Although, arbuscular mycorrhizal fungi (AMF) are important for plant stress resistance; but the mechanisms by which AMF alleviate Se stress in crop seedlings are unclear. Therefore, we investigated the potential strategies of AMF symbiosis to alleviate Se stress in maize (Zea mays) from plants and soil perspectives. Results showed that Se stress (Se application level > 5 mg kg−1) significantly inhibited leaf area, shoot dry weight, and root dry weight of maize (P < 0.05). In contrast, AM symbiosis significantly improved root morphology, increased nitrogen and phosphorus nutrition, promoted shoot growth, inhibited the transport of Se from soil/roots to shoots, and then diluted the concentration of Se in shoots (32.65–52.80%). In general, the response of maize growth to AMF was mainly observed in shoots rather than roots. In addition, AMF inoculation significantly increased the easily extractable glomalin-related soil protein and organic matter contents and decreased the availability of soil Se to the plant. Principal component analysis showed that AMF promoted growth and nutrition uptake of maize was the most dominant effect of Se stress alleviation, followed by the decrease of soil Se availability, limiting Se transport from soil/roots to shoots. Moreover, the expression of Se uptake-related ion transporter genes (ZmPht2, ZmNIP2;1, and ZmSultr1;3) in maize roots were down-regulated upon AM symbiosis which resultantly inhibited the uptake and transport of Se from soil to maize roots. Thus, AMF could impede Se stress in maize seedlings by improving plant and soil characteristics.

Stimulation of Nicotiana tabacum L. In Vitro Shoot Growth by Endophytic Bacillus cereus Group Bacteria.

In vitro plant tissue cultures face various unfavorable conditions, such as mechanical damage, osmotic shock, and phytohormone imbalance, which can be detrimental to culture viability, growth efficiency, and genetic stability. Recent studies have revealed a presence of diverse endophytic bacteria, suggesting that engineering of the endophytic microbiome of in vitro plant tissues has the potential to improve their acclimatization and growth. Therefore, the aim of this study was to identify cultivated tobacco (Nicotiana tabacum L.) endophytic bacteria isolates that are capable of promoting the biomass accumulation of in vitro tobacco shoots. Forty-five endophytic bacteria isolates were obtained from greenhouse-grown tobacco plant leaves and were assigned to seven Bacillus spp. and one Pseudomonas sp. based on 16S rRNA or genome sequence data. To evaluate the bacterial effect on in vitro plant growth, tobacco shoots were inoculated with 22 isolates selected from distinct taxonomic groups. Four isolates of Bacillus cereus group species B. toyonensis, B. wiedmannii and B. mycoides promoted shoot growth by 11–21%. Furthermore, a contrasting effect on shoot growth was found among several isolates of the same species, suggesting the presence of strain-specific interaction with the plant host. Comparative analysis of genome assemblies was performed on the two closely related B. toyonensis isolates with contrasting plant growth-modulating properties. This revealed distinct structures of the genomic regions, including a putative enzyme cluster involved in the biosynthesis of linear azol(in)e-containing peptides and polysaccharides. However, the function of these clusters and their significance in plant-promoting activity remains elusive, and the observed contrasting effects on shoot growth are more likely to result from genomic sequence variations leading to differences in metabolic or gene expression activity. The Bacillus spp. isolates with shoot-growth-promoting properties have a potential application in improving the growth of plant tissue cultures in vitro.

Gentianella lutescens subsp. carpatica J. Holub.: Shoot Propagation In Vitro and Effect of Sucrose and Elicitors on Xanthones Production.

In vitro shoot culture of the endangered medicinal plant Gentianella lutescens was established from epicotyl explants cultured on MS basal medium with 0.2 mg L−1 6-benzylaminopurine (BA) and evaluated for xanthones content for the first time. Five shoot lines were obtained and no significant variations in multiplication rate, shoot elongation, and xanthones profile were found among them. The highest rooting rate (33.3%) was achieved by shoots treated for 2 days with 5 mg L−1 indole-3-butyric acid (IBA) followed by cultivation in liquid PGR-free ½ MS medium for 60 days. HPLC analysis revealed the lower content of xanthones—mangiferin, bellidifolin, demethylbellidifolin, demethylbellidifolin-8-O-glucoside and bellidifolin-8-O-glucoside—in in vitro cultured shoots compared to wild growing plants. The increasing concentration of sucrose, sorbitol and abiotic elicitors salicylic acid (SA), jasmonic acid (JA) and methyl jasmonate (MeJA) altered shoot growth and xanthone production. Sucrose and sorbitol applied at the highest concentration of 233.6 mM increased dry matter percentage, while SA at 100 μM promoted shoot growth 2-fold. The increased sucrose concentration enhanced accumulation of xanthones in shoot cultures 2–3-fold compared to the control shoots. Elicitors at 100–300 μM increased the accumulation of mangiferin, demethylbellidifolin-8-O-glucoside, and bellidifolin-8-O-glucoside almost equally, while MeJA at the highest concentration of 500 μM enhanced amount of aglycones demethylbellidifolin and bellidifolin 7-fold compared to the control. The obtained results facilitate conservation of G. lutescens and pave the way for further research on large-scale shoot propagation and production of pharmacologically active xanthones.

The outstanding rooting1 mutation gene maintains shoot growth and grain yield through promoting root development in rice under water deficit field environments

AbstractDrought is one of the most serious constraints to rice cultivation, even under alternate wetting and drying (AWD), which is a water‐saving management practice. In rice, enhanced root development is essential for stable shoot growth, adaptability and productivity under water deficit environments. We identified and characterized outstanding rooting1 (our1) rice mutant using hydroponics. The present study sought to examine morphological root traits of the our1 mutant and the role of the mutation gene in shoot growth and yield under AWD. Thus, we evaluated the growth performance of the our1 rice mutant in pot experiments and under field AWD conditions in Kenya. The experiments were conducted with our1 mutant, its wild type and their progenies under both AWD and continuously waterlogged (CWL) conditions. The our1 mutant possessed a well‐developed root system and exhibited particularly enhanced thin root development, which was maintained from the early vegetative stage through the reproductive stage under both pot and field AWD management. This enhanced root development promoted shoot growth through increased water uptake during rewatered conditions between drought periods in AWD. In addition, the our1 mutant showed enhanced shoot growth during the reproductive stage, resulting in the maintenance of yield under AWD fields. Genotypes harbouring our1 mutation gene showed higher yields compared to wild‐type genotypes which was attributed to their higher photosynthetic ability as a result of enhanced root activity. These results suggest the important role of a well‐developed root system architecture and enhanced root function in stabilizing rice yields under water‐limited environments. Our findings indicate that the our1 mutation gene can serve as a novel breeding material to mitigate the impact of transient drought stress on yield under AWD.

PtBRI1.2 promotes shoot growth and wood formation through a brassinosteroid-mediated PtBZR1-PtWNDs module in poplar.

Brassinosteroid-insensitive-1 (BRI1) plays important roles in various signalling pathways controlling plant growth and development. However, the regulatory mechanism of BRI1 in brassinosteroid (BR)-mediated signalling for shoot growth and wood formation in woody plants is largely unknown. In this study, PtBRI1.2, a brassinosteroid-insensitive-1 gene, was overexpressed in poplar. Shoot growth and wood formation of transgenic plants were examined and the regulatory genes involved were verified. PtBRI1.2 was localized to the plasma membrane, with a predominant expression in leaves. Ectopic expression of PtBRI1.2 in Arabidopsis bri1-201 and bri1-5 mutants rescued their retarded-growth phenotype. Overexpression of PtBRI1.2 in poplar promoted shoot growth and wood formation in transgenic plants. Further studies revealed that overexpression of PtBRI1.2 promoted the accumulation of PtBZR1 (BRASSINAZOLE RESISTANT1) in the nucleus, which subsequently activated PtWNDs (WOOD-ASSOCIATED NAC DOMAIN transcription factors) to up-regulate expression of secondary cell wall biosynthesis genes involved in wood formation. Our results suggest that PtBRI1.2 plays a crucial role in regulating shoot growth and wood formation by activating BR signalling.

Lysinibacillus xylanilyticus Strain GIC41 as a Potential Plant Biostimulant.

To identify Lysinibacillus strains with the potential to function as plant biostimulants, we screened 10 previously isolated Lysinibacillus strains from the rhizosphere and soil for their plant growth-promoting (PGP) effects. In vitro tests showed that all strains produced indole-3-acetic acid. In primary screening, the PGP effects of these strains were assessed on spinach seedlings grown on Jiffy-7 pellets; strains GIC31, GIC41, and GIC51 markedly promoted shoot growth. In secondary screening, the PGP efficacies of these three strains were examined using spinach seedlings grown in pots under controlled conditions. Only GIC41 exerted consistent and significant PGP effects; therefore, it was selected for subsequent experiments. The results of 6-week glasshouse experiments revealed that GIC41 markedly increased shoot dry weight by ca. 12–49% over that of the control. The impact of fertilization levels on the PGP efficacy of GIC41 was investigated using pot experiments. The application of a specific level of fertilizer was required for the induction of sufficient PGP effects by this strain. The phylogenetic ana­lysis based on the 16S rDNA sequence identified GIC41 as L. xylanilyticus. Collectively, these results show the potential of strain GIC41 to function as a plant biostimulant.