Root Research Articles

Phytotoxicity of Prussian blue nanoparticles to rice and the related defence mechanisms: In vivo observations and physiological and biochemical analysis

While the nanotoxic effects on plants have been extensively studied, the underlying mechanisms of plant defense responses and resistance to nanostress remain insufficiently understood. Particularly, Prussian blue nanoparticles (PB NPs) have been extensively used in pigments, pharmaceuticals, electrocatalysis, biosensors and energy storage. However, the impact of PB NPs on plants’ health and growth are largely unknown. Herein, the phytotoxicity of PB NPs to rice and trace the uptake, accumulation and biotransformation of PB NPs was explored, along with the underlying defence mechanisms. The results showed that PB NPs (≥ 50 mg L–1) significantly inhibited the growth of rice seedling up to 16.16%, 27.80%, and 29.37% in plant height, shoot biomass and root biomass, respectively. The X-ray spectroscopic studies and in vivo elemental and particle-imaging demonstrated that PB NPs were transported through the cortex via xylem from root to shoot. However, most of the PB NPs and their transformation products were retained in the root, where they were blocked owing to root cell wall (RCW) remodelling, and 81.4%-83.4% of Fe accumulated in the RCW compared to 66.6% in the control. Specifically, PB NPs stimulated pectin methylesterase activity by promoting hydrogen peroxide production to participate in RCW remodeling. More interestingly, Si was specifically regulated to covalently bind to hemicellulose to form the Si-hemicellulose complex that strongly bound with PB NPs during RCW remodeling, resulting in the strong defense against PB NPs. These findings provide new insights into the phytotoxicity of artificial NPs and the defense mechanisms of plants.

The Impact of Supplemental UV-B Radiation on Growth and Biochemical Constituents in Vigna unguiculata L. Walp and Pisum sativum L.

This study investigates the impact of UV-B radiation on plant growth and biochemical constituents in Vigna unguiculata and Pisum sativum plants grown from non-irradiated and UV-B-irradiated seeds. The results show that plants grown from UV-B-irradiated seeds for 30, 60, and 90minutes experienced significant reductions in plant height, root length, and shoot length compared to non-irradiated seeds. Additionally, plants with UV-B-irradiated seeds had less fresh and dry weight. The decline was particularly pronounced in plants exposed to UV-B radiation for 90minutes. Chlorophyll a, b, and total chlorophyll (a+b) dropped significantly in plants grown from seeds exposed to UV-B radiation for 30, 60, and 90minutes. The reduction was particularly significant in plants exposed to UV-B radiation for 90minutes. Moreover, plants with higher levels of total free phenolics and tannins had higher contents compared to non-irradiated seeds. The level of total free phenols is higher in irradiated seeds of P. sativum than V. unguiculata. The plants exposed to UV-B radiation for 90minutes showed a noticeable increase.

Arbuscular mycorrhizal fungi influence belowground interactions between a specialist root-feeder and its natural enemy

As primary producers, plants play a central role in mediating interactions across trophic levels. Although plants are the primary food source for herbivorous insects, they can protect themselves from herbivore damage. Many plants produce toxic compounds that directly reduce herbivore feeding, but plants also protect themselves indirectly by attracting natural enemies of the attacking herbivore through volatile signaling. These so-called tri-trophic interactions have historically been documented aboveground in aerial plant parts but are also known to occur belowground in root systems. In addition to herbivores, plants directly interact with other organisms, which can influence the outcomes of tri-trophic interactions. Arbuscular mycorrhizal fungi (AMF) are symbiotic soil microbes that colonize the roots of plants and facilitate nutrient uptake. These microbes can alter plant chemistry and subsequent resistance to herbivores. Few studies, however, have shown how AMF affect tri-trophic interactions above- or belowground. This study examines how AMF colonization affects the emission of root volatiles when plants are under attack by western corn rootworm, a problematic pest of corn, and subsequent attraction of entomopathogenic nematodes, a natural enemy of western corn rootworm. Mycorrhizal fungi increased rootworm survival but decreased larval weight. Differences were detected across root volatile profiles, but there was not a clear link between volatile signaling and nematode behavior. Nematodes were more attracted to non-mycorrhizal plants without rootworms and AMF alone in soil, suggesting that AMF may interfere with cues that are used in combination with volatiles which nematodes use to locate prey.

Biogeochemical sulfur transformations in the cohesive and permeable tidal flat sediments of Jade Bay (North Sea)

Intertidal flats are highly productive coastal marine ecosystems which are affected by fast changes in environmental conditions and host dynamic biogeochemical cycles in their sediments. Bioturbation by burrowing organisms and roots of plants strongly affects speciation and cycling of redox-sensitive elements in intertidal sediments. In this work, we have studied the impact of sediment type and vegetation on the cycling of redox-sensitive elements including sulfur, iron, and manganese in sandy and muddy tidal flats sediments in the Jade Bay (North Sea) and adjacent area. The redox speciation of these elements was analyzed in the pore-waters and the total sediment. The isotopic compositions of sulfur species were measured in non-vegetated sediments and in sediments which are inhabited by various plants. In the cohesive sediments, which are not affected by vegetation, a decrease in sulfate concentration, coupled with the presence of relatively high concentrations of hydrogen sulfide in the pore-waters and the presence of sulfide minerals as well the isotopic compositions of sulfur species are consistent with fast rates of sulfate reduction in the sediments. In the cohesive sediments affected by roots of Salicornia stricta and sediments desiccation, a cryptic sulfur cycle, which is characterized by microbial sulfate reduction coupled to fast reoxidation of hydrogen sulfide by Fe(III) (hydr)oxides and, possibly, by oxygen is present. Below the roots penetration depth, speciation of redox-sensitive elements is similar to those in the baren sediments. In the cohesive sediments affected by the roots of Spartina anglica and Triglochin maritima, which have longer roots, a cryptic sulfur cycle was detected in the upper 30 cm of sediments. At the sites that are characterized by permeable surface sediments and alternating permeable and cohesive layers in the deeper sediments, the composition of the sediment has a similar or even more significant impact on the speciation of the redox-sensitive elements than penetration of relatively weak roots of Spartina anglica. These sediments are characterized by the formation of hydrogen sulfide and sulfide oxidation intermediates in the cohesive layers and their diffusion to (and oxidation at) the boundaries between cohesive and permeable sediments. We conclude that in the cohesive sediment, the penetration of roots and desiccation leads to the formation of overall oxidized conditions in the sediments, while in the sediments with alternating layers, permeability may provide a more significant control for speciation of redox-sensitive elements.

The addition of humic acid into soil contaminated with microplastics enhanced the growth of black gram (Vigna mungo L. Hepper) and modified the rhizosphere microbial community.

Microplastics have polluted agricultural soils, posing a substantial risk to crop productivity. Moreover, the presence of microplastic pollution has caused a disturbance in the composition of the microbial community in the soil surrounding plant roots, therefore impacting the growth of beneficial bacteria. A study was conducted to examine if humic acid (HA) can counteract the harmful effects of microplastics (MPs) on the growth of black gram crops and the composition of the rhizosphere soil microbial community, to reduce the negative impacts of microplastics on these microorganisms and crops. The research was carried out using mud pots and the plastic utilized for the experiment consisted of 60% high-density polyethylene (HDPE) and 40% polypropylene (PP). The soil was enriched with lignite-based potassium humate, which had a pH range of 8.0-9.5 and with 65% humic acid. The experiment consisted of six treatments: T1, which served as the control without HA and MP; T2, which involved the use of HA at a concentration of 0.15% w/w; T3, which involved the use of MP at a concentration of 0.2% w/w; T4, which involved the use of MP at a concentration of 0.4% w/w; T5, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.2% w/w; and T6, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.4% w/w. The plant growth characteristics, including germination percentage, nodule number, and chlorophyll content, were measured. In addition, the DNA obtained from the rhizosphere soil was analyzed using metagenomics techniques to investigate the organization of the microbial population. Seedlings in soil polluted with MP exhibited delayed germination compared to seedlings in uncontaminated soil. Following 60days of growth, the soil samples treated with T5 (0.2% MP and 0.15% HA w/w) had the highest population of bacteria and rhizobium, with counts 5.58 ± 0.02 and 4.90 ± 0.02CFUg-1 soil. The plants cultivated in T5 had the most elevated chlorophyll-a concentration (1.340 ± 0.06mgg-1), and chlorophyll-b concentration (0.62 ± 0.02mgg-1) while those cultivated in T3 displayed the lowest concentration of chlorophyll-a (0.59 ± 0.02mgg-1) and chlorophyll-b (0.21 ± 0.04mgg-1). Within the phylum, Proteobacteria had the highest prevalence in all treatments. However, when the soil was polluted with MPs, its relative abundance was reduced by 8.4% compared to the control treatment (T1). Conversely, treatment T5 had a 3.76% rise in relative abundance when compared to treatment T3. The predominant taxa found in soil polluted with MP were Sphingomonas and Bacillus, accounting for 19.3% of the total. Sphingomonas was the predominant genus (21.2%) in soil polluted with MP and supplemented with humic acid. Humic acid can be used as a soil amendment to mitigate the negative effects of MPs and enhance their positive advantages. Research has demonstrated that incorporating humic acid into soil is a viable method for maintaining the long-term integrity of soil's physical, chemical, and biological characteristics.

Flg22-facilitated PGPR colonization in root tips and control of root rot.

Plant root border cells (RBCs) prevent the colonization of plant growth-promoting rhizobacteria (PGPR) at the root tip, rendering the PGPR unable to effectively control pathogens infecting the root tip. In this study, we engineered four strains of Pseudomonas sp. UW4, a typical PGPR strain, each carrying an enhanced green fluorescent protein (EGFP)-expressing plasmid. The UW4E strain harboured only the plasmid, whereas the UW4E-flg22 strain expressed a secreted EGFP-Flg22 fusion protein, the UW4E-Flg(flg22) strain expressed a non-secreted Flg22, and the UW4E-flg22-D strain expressed a secreted Flg22-DNase fusion protein. UW4E-flg22 and UW4E-flg22-D, which secreted Flg22, induced an immune response in wheat RBCs and colonized wheat root tips, whereas the other strains, which did not secrete Flg22, failed to elicit this response and did not colonize wheat root tips. The immune response revealed that wheat RBCs synthesized mucilage, extracellular DNA, and reactive oxygen species. Furthermore, the Flg22-secreting strains showed a 33.8%-93.8% higher colonization of wheat root tips and reduced the root rot incidence caused by Rhizoctonia solani and Fusarium pseudograminearum by 24.6%-35.7% compared to the non-Flg22-secreting strains in pot trials. There was a negative correlation between the incidence of wheat root rot and colonization of wheat root tips by these strains. In contrast, wheat root length and dry weight were positively correlated with the colonization of wheat root tips by these strains. These results demonstrate that engineered secretion of Flg22 by PGPR is an effective strategy for controlling root rot and improving plant growth.

A synthetic bacterial community engineered from Miscanthus floridulus roots enhances ammonia nitrogen removal in ionic rare earth mine tailings

Ammonium sulfate, as the primary leaching agent, has caused significant nitrogen pollution in rare earth elements (REEs) mining areas. Phytoremediation is a promising remediation method, relying on the synergistic relationships between plants and their root-associated microbiome. Nevertheless, harnessing the microbiome to accelerate nitrogen transformation and absorption by plants is challenging. Here, we investigated the composition, activities and culturable fraction of the root bacterial microbiome of the pioneer plant Miscanthus floridulus grown in a REEs tailing soil containing a high ammonia nitrogen (AN) concentration at 344.35 mg kg−1. Based on this, we constructed a simplified synthetic microbial community (SynCom) derived from the roots of M. floridulus, possessing nitrification and denitrification capabilities, to help REEs mine plants efficiently convert pollutant AN into nutrients, thereby enhancing plant growth and AN removal. This SynCom, consisting of 10 bacterial strains, included species of the genera Burkholderia (5) Paraburkholderia (1), Curtobacterium (1), Leifsonia (1) and Sinomonas (2). As a result, this SynCom alone achieved a significant reduction of 24.8% in AN content in tailing soil. When the SynCom inoculated with plants, the reduction in AN was even more significant (32.6%), surpassing the reduction achieved solely by plants (25.5%). Moreover, live SynCom inoculation significantly increased shoot and root biomass by 39.8% and 49.7%, respectively, compared to dead SynCom inoculation. These results indicate that the reduction in AN can be attributed to the SynCom's nitrification and denitrification capabilities, as well as its ability to enhance plant nitrogen absorption by stimulating their growth. Notably, seven nitrifying and denitrifying strains of the SynCom are particularly enriched, suggesting that plant roots selectively recruit nitrogen cycle-related bacteria to accelerate nitrogen transformation and absorption. These results provide a practical solution for harnessing the synergistic relationships between plants and their root microbiome in environmental remediation efforts.

Soil metabolic processes influenced by rice roots co-regulates the environmental evolution of antibiotic resistome

Plant root activities lead to significant differences in metabolites between the rhizosphere and non-rhizosphere soil, profoundly affecting microbial distribution. However, how this process drives the migration and propagation of manure-derived antibiotic resistance genes (ARGs) in farmland ecosystems remains unclear. Herein, we used a rice pot microcosm experiment to explore the characteristics of antibiotic resistome and bacterial communities in rhizosphere and non-rhizosphere soils and the driving effects of rhizosphere metabolites on ARG propagation. The results showed significant differences in some ARGs and bacterial diversity in rhizosphere and non-rhizosphere soils with varied differential ARGs between different growth stages of rice (P < 0.05). The biosynthesis of secondary metabolites and glutathione metabolism were found to be the main pathways affecting ARG differences in rhizosphere and non-rhizosphere soils under manure application. Structural equation modeling (SEM) analysis further indicated that ARG distribution differences between rhizosphere and non-rhizosphere soils were mainly regulated by differential metabolites, which influenced the ARG distribution by altering the succession of soil microbial communities. These results demonstrate the role of differential metabolites resulting from rice root activities in co-regulating ARG distribution, providing new insights into the regulatory mechanisms of soil ARG dynamics in paddy fields.

PENGARUH LARUTAN PUPUK HAYATI ENDOMIKORIZA ASAL AKAR MERANTI TERHADAP PERTUMBUHAN DAN PRODUKSI TANAMAN KANGKUNG

Water spinach (Ipomoea sp) is a plant that is widely consumed by people as a vegetable because it is cheap and easy to cultivate. The main problems in growing water spinach are soil fertility and attack by plant pests and diseases. To increase production from kale farming, farmers generally use inorganic fertilizers such as NPK which in reality can cause environmental pollution. For this reason, various efforts to use organic (environmentally friendly) fertilizers such as fungal and bacterial biofertilizers remain the focus of research to date. Mycorrhizal fungi are known to have quite a lot of benefits for plants, especially in providing phosphate and nitrogen nutrients for host plants. In the forestry sector, it is known that the roots of meranti plants (Shorea sp) and the roots of pine plants (Pinus sp) are natural hosts for the growth and development of mycorrhizal fungi. Therefore, the aim of this research is to determine the effect of endomycorrhizal solution fertilizer from meranti roots on the growth and production of water spinach plants. The results of the research show that the endomycorrhizal biofertilizer solution from meranti roots produces growth and production of water spinach plants that are not significantly different from the NPK fertilizer treatment, so from an environmental safety aspect, it is proposed that it is better to use endomycorrhizal biofertilizer because it is environmentally friendly.

Mechanisms by Which Increased pH Ameliorates Copper Excess in Citrus sinensis Roots: Insight from a Combined Analysis of Physiology, Transcriptome, and Metabolome

Limited data are available on copper (Cu)–pH interaction-responsive genes and/or metabolites in plant roots. Citrus sinensis seedlings were treated with 300 μM (Cu toxicity) or 0.5 μM (control) CuCl2 at pH 3.0 or 4.8 for 17 weeks. Thereafter, gene expression and metabolite profiles were obtained using RNA-Seq and widely targeted metabolome, respectively. Additionally, several related physiological parameters were measured in roots. The results indicated that elevating the pH decreased the toxic effects of Cu on the abundances of secondary metabolites and primary metabolites in roots. This difference was related to the following several factors: (a) elevating the pH increased the capacity of Cu-toxic roots to maintain Cu homeostasis by reducing Cu uptake and Cu translocation to young leaves; (b) elevating the pH alleviated Cu toxicity-triggered oxidative damage by decreasing reactive oxygen species (ROS) formation and free fatty acid abundances and increasing the ability to detoxify ROS and maintain cell redox homeostasis in roots; and (c) increasing the pH prevented root senescence and cell wall (CW) metabolism impairments caused by Cu toxicity by lowering Cu levels in roots and root CWs, thus improving root growth. There were some differences and similarities in Cu–pH interaction-responsive genes and metabolites between leaves and roots.

Research on the Mechanisms of Phytohormone Signaling in Regulating Root Development

Phytohormones are organic compounds produced in trace amounts within plants that regulate their physiological processes. Their physiological effects are highly complex and diverse. They influence processes ranging from cell division, elongation, and differentiation to plant germination and rooting. Therefore, phytohormones play a crucial regulatory role in plant growth and development. Recently, various studies have highlighted the role of PHs, such as auxin, cytokinin (CK), and abscisic acid (ABA), and newer classes of PHs, such as brassinosteroid (BR) and peptide hormone, in the plant responses toward environmental stresses. These hormones not only have distinct roles at different stages of plant growth but also interact to promote or inhibit each other, thus effectively regulating plant development. Roots are the primary organs for water and mineral absorption in plants. During seed germination, the radicle breaks through the seed coat and grows downward to form the primary root. This occurs because the root needs to quickly penetrate the soil to absorb water and nutrients, providing essential support for the plant’s subsequent growth. Root development is a highly complex and precisely regulated process influenced by various signals. Changes in root architecture can affect the plant’s ability to absorb nutrients and water, which in turn impacts crop yield. Thus, studying the regulation of root development is of great significance. Numerous studies have reported on the role of phytohormones, particularly auxins, in root regulation. This paper reviews recent studies on the regulation of root development by various phytohormones, both individually and in combination, providing a reference for researchers in this field and offering perspectives on future research directions for improving crop yields.

SydR, a redox-sensing MarR-type regulator of Sinorhizobium meliloti, is crucial for symbiotic infection of Medicago truncatula roots.

Rhizobia associate with legumes and induce the formation of nitrogen-fixing nodules. The regulation of bacterial redox state plays a major role in symbiosis, and reactive oxygen species produced by the plant are known to activate signaling pathways. However, only a few redox-sensing transcriptional regulators (TRs) have been characterized in the microsymbiont. Here, we describe SydR, a novel redox-sensing TR of Sinorhizobium meliloti that is essential for the establishment of symbiosis with Medicago truncatula. SydR, a MarR-type TR, represses the expression of the adjacent gene SMa2023 in growing cultures, and this repression is alleviated by NaOCl, tert-butyl hydroperoxide, or H2O2 treatment. Transcriptional psydR-gfp and pSMa2023-gfp fusions, as well as gel shift assays, showed that SydR binds two independent sites of the sydR-SMa2023 intergenic region. This binding is redox-dependent, and site-directed mutagenesis demonstrated that the conserved C16 is essential for SydR redox sensing. The inactivation of sydR did not alter the sensitivity of S. meliloti to NaOCl, tert-butyl hydroperoxide, or H2O2, nor did it affect the response to oxidants of the roGFP2-Orp1 redox biosensor expressed within bacteria. However, in planta, ΔsydR mutation impaired the formation of root nodules. Microscopic observations and analyses of plant marker gene expression showed that the ΔsydR mutant is defective at an early stage of the bacterial infection process. Altogether, these results demonstrated that SydR is a redox-sensing MarR-type TR that plays a key role in the regulation of nitrogen-fixing symbiosis with M. truncatula.IMPORTANCEThe nitrogen-fixing symbiosis between rhizobia and legumes has an important ecological role in the nitrogen cycle, contributes to nitrogen enrichment of soils, and can improve plant growth in agriculture. This interaction is initiated in the rhizosphere by a molecular dialog between the two partners, resulting in plant root infection and the formation of root nodules, where bacteria reduce the atmospheric nitrogen into ammonium. This symbiosis involves modifications of the bacterial redox state in response to reactive oxygen species produced by the plant partner. Here, we show that SydR, a transcriptional regulator of the Medicago symbiont Sinorhizobium meliloti, acts as a redox-responsive repressor that is crucial for the development of root nodules and contributes to the regulation of bacterial infection in S. meliloti/Medicago truncatula symbiotic interaction.

Ectopic expression of the GRAS-type transcriptional regulator NSP2 in Parasponia triggers contrasting effects on symbioses

IntroductionPlants strictly control root endosymbioses with nutrient-scavenging arbuscular endomycorrhizal fungi or nodule inducing diazotrophic bacteria. The GRAS-type transcriptional regulator NODULATION SIGNALING PATHWAY 2 (NSP2) is a conserved hub in this process. The NSP2-regulated transcriptional network is instrumental in balancing nutrient homeostasis with symbiotic interactions. NSP2 activity is modulated post-transcriptionally by a specific microRNA. Overriding this control mechanism by ectopic expression of a miRNA-resistant NSP2 transgene enhances the symbiotic permissiveness to arbuscular endomycorrhizal fungi. Such engineered plants may possess enhanced capacities for nutrient uptake. However, the trade-off of this strategy on plant development or other symbiotic interactions, like nodulation, is yet to be fully understood.MethodWe used the nodulating Cannabaceae species Parasponia andersonii as an experimental system to study the effect of ectopic NSP2 expression. Parasponia and legumes (Fabaceae) diverged 100 million years ago, providing a unique comparative system to dissect the nodulation trait.ResultsSix independent transgenic Parasponia lines were generated that differed in the level of NSP2 expression in the root from 6 to 95-fold higher when compared to the empty vector control plants. Analysis of these plants revealed a positive correlation between mycorrhization and the NSP2 expression level, as well as with the expression of the symbiosis transcription factor CYCLOPS and the rate-limiting enzyme in the carotenoid biosynthetic pathway PHYTOENE SYNTHASE1 (PSY1). Yet ectopic expression of NSP2 affected plant architecture and root nodule organogenesis.DiscussionThis indicates a significant trade-off when leveraging NSP2 over-expression to enhance endomycorrhization.

Biochar Organic Fertilizer Combined with Indigenous Microorganisms Enhances the Growth of Landscape Grass Cultivated in a Substrate Mixed with Iron Tailings and Mining Topsoil

Iron tailings from the mining process occupy vast land areas and pose a significant ecological risk. In order to reuse iron tailings resources and carry out in situ ecological restoration of a mine, in this study, a medium of mixed iron tailings and mining topsoil (m:m = 3:1) was used to plant landscape grasses, including Lolium perenne L. (L. perenne), Pennisetum alopecuroides (L.) Spreng. (P. alopecuroides), Melilotus officinalis (L.) Lam. (M. officinalis), and Medicago sativa L. (M. sativa). Biochar and chicken manure were used as biochar organic fertilizers and indigenous microorganisms were isolated from the rhizosphere soil of tested grasses. They were applied to enhance landscape grass growth by regulating rhizosphere microbial communities and nutrient conditions. The results showed that the biochar organic fertilizers significantly promoted the growth of the four landscape grasses, notably P. alopecuroides, increasing plant height, root length, root weight, and leaf fresh weight by 169%, 60%, 211%, and 388%, respectively. Additionally, L. perenne exhibited the greatest height increase (10%) following the application of bacterial solutions. Moreover, indigenous bacterial solutions enhanced chlorophyll content and phenylalanine ammonia-lyase (PAL) activity, with P. alopecuroides showing the highest chlorophyll increase of 58% and M. sativa exhibiting a 30.58% rise in PAL activity. The biochar organic fertilizer also significantly elevated soluble protein content in P. alopecuroides and M. sativa by 195% and 152%, respectively. It also effectively enhanced peroxidase (POD) activity in Poaceae grasses by 120% to 160%. After adding indigenous microorganisms, the rhizosphere soil of the landscape grass showed the highest Shannon–Wiener diversity index, reaching 3.561. The rhizosphere soil of M. officinalis had the highest microbial richness, with a value of 39. Additionally, the addition of indigenous microorganisms increased the nitrogen, phosphorus, and potassium content of the four plants by 8–19%, 6–14%, and 8–18%, respectively. This study offers a new approach for managing mining waste and ecological restoration in mining areas.

Phosphorus Supply Under Micro-Nano Bubble Water Drip Irrigation Enhances Maize Yield and Phosphorus Use Efficiency

This study aimed to explore the combined effects of micro-nano bubble water drip irrigation and different phosphorus (P) application rates (P0: 0 kg·hm−2; P1: 86 kg·hm−2; P2: 172 kg·hm−2; P3: 258 kg·hm−2) on maize growth, soil phosphorus dynamics, and phosphorus use efficiency to optimize irrigation and P fertilizer use efficiency. Through a field column experiment, the impact of micro-nano bubble water drip irrigation on maize plant height, stem diameter, leaf SPAD values, biomass, and yield was evaluated. The results showed that (1) irrigation methods significantly affected maize growth indicators such as plant height, stem diameter, and root dry weight. Micro-nano bubble water drip irrigation consistently promoted growth during all growth stages, especially under higher P application. (2) P application significantly increased the dry weight and P concentration in maize roots, stems, leaves, ears, and grains. Under micro-nano bubble water drip irrigation, the P concentrations in roots and grains increased by 59.28% to 92.59%. (3) Micro-nano bubble water drip irrigation significantly enhanced P uptake efficiency, partial factor productivity of P, and agronomic P use efficiency. Particularly under P1 and P2 treatments, the increases were 134.91% and 45.42%, respectively. Although the effect on apparent P recovery efficiency was relatively small, micro-nano bubble water drip irrigation still improved P utilization under moderate P levels. (4) Structural equation modeling indicated that P supply under micro-nano bubble water drip irrigation primarily regulated alkaline protease and alkaline phosphatase, enhancing soil P availability, which in turn promoted maize P accumulation and increased yield. In conclusion, this study demonstrated that the combination of micro-nano bubble water drip irrigation and appropriate P application can effectively promote maize growth and nutrient utilization, providing a theoretical basis for optimizing irrigation and fertilization strategies in maize production.

Inoculation of Arthrobacter sp. improves the growth of Acanthocalycium sp. and the fruits nutraceutical quality and the flowers longevity

Research objective: The aim of this work is on the inoculation in the growing medium of Arthrobacter sp. and its effects on the growth, flower quality and longevity of cactus plants. To this end, the study of biometric parameters, i.e. plants and flowers (height, weight, number and duration), as well as root growth (weight), and the presence of disease were quantified as measures of plant productivity and compared with those obtained from non-inoculated plants. The use of alginate microspheres as a means of bacterial inoculation was also considered. Materials and Methods: Seedlings of Acanthocalycium (2 years old) Ferrarii, A. Glaucum and A. Violaceum were immediately planted in pots after purchase, in substrate containing (sand 20%, pumice 20% and peat 60%; pH 7; electrical conductivity 0.7 dS/m; total porosity 80% (v/v). A randomised complete block design was applied for the experiments: the pots were randomly divided into two series, one series was inoculated with the bacteria and the other non-inoculated was used as a control. Each month, plant growth was assessed according to (1) plant height, (2) vegetative and root weight, (3) number of flowers per plant (4) flower duration. In addition, the occurrence of possible diseases, in particular Fusarium sp. and Verticillium sp., was assessed. Total flavonoids, total phenols and antioxidant activity were also analysed. Results and Discussion: The experiment showed that the use of Arthrobacter sp. can indeed significantly improve the vegetative and root growth of Acanthocalycium sp. cacti. In addition, there was a significant improvement in the number and floral longevity as well as in the phenol, flavonoid and antioxidant content of the fruits of the inoculated plants compared to the untreated control. The experiment also showed that mortality due to the pathogens Fusarium sp. and Verticillium sp. was significantly reduced in the treated plant. In agreement with these authors, we found that PGPB treatments increased agronomic parameters and improved Fusarium and Verticillium resistance. In general, the application of biostimulants can increase the synthesis of bioactive compounds in plants by increasing resistance to phytopathologies. Inoculation with Arthrobacter sp. led to a significant reduction in the number of dead plants with respect to the diseases analysed. As a result of the stimulating action demonstrated in Acanthocalycium, bioproducts suitable for nutraceutical purposes may be developed in the future. Therefore, new microbe-assisted technologies can help plants to resist stress conditions, improving their tolerance and productivity. Conclusions: Due to its ‘multifunctionality’, the genus Acanthocalycium is considered as one of the species of the future, for ornamental use and medicinal aspects, and new results may help reveal its potential in the context of the bio-economy and circular economy. As natural resources and cultural practices are crucial in defining the quality of flowers when destined for food/nutraceutical applications, the inoculation of Acanthocalycium with Arthrobacter sp. can be envisaged to provide better plant growth under conditions of environmental stress, or as a soil fertiliser, but also to improve the synthesis of natural products used for therapeutic applications.

Study of the importance of plants with tubers and edible roots in the life of local populations in the Nimba Mountains Biosphere Reserve

This study focusing on root and tuber plants in the riverside villages of Nimba aims to promote the importance of roots and tubers in the lives of people living near the UNESCO heritage site, Nimba Mountains Biosphere Reserve. . The method of collecting data from resource people and the focus group through a questionnaire developed using the Kobocollect tool was used. The survey concerned 190 people including 79 women or 41.58% who were grouped into age groups with an interval of 5 years and the age group over 20 years was the most interested with 143 people or 75 .26% of respondents. Among all agricultural productions, cassava ranks first (42%), followed by taro (30%), sweet potato (18%) and yam (10%) the least cultivated due to lack of knowledge of its cultivation method, which allows us to affirm that roots and tubers have a primordial place in the nimba zone. The adaptation of these crops to the difficult conditions of the area, their nutritional energy value and their economic contribution deserve the encouragement of these crops despite the difference in yield between these four crops. So for the development of these cultures, authorities at all levels, NGOs, businesses etc. must strengthen the technical and financial capacity of producers, by forming groups or cooperatives, providing them with improved seeds and inputs.

Techno-economic study for photovoltaic battery-free irrigation systems in an arid area for olive fields in Western West Al Minya, Egypt

Due to rain scarcity, artificial irrigation became an environmentally critical application for crop production. Proper irrigation is essential to maximize water use efficiency and plant biomass. Using clean energy sources is currently a trend that is sweeping the globe. To achieve this, we propose a solar-powered irrigation system. This study considers alternative irrigation systems using photovoltaic solar systems to pump water from deep wells for new land reclamation, whereas groundwater is the only source. The main objective is to evaluate various PV-powered pumping systems in Egypt's Western West Al Minya area. Two systems were nominated by considering the annual savings: the conventional irrigation Diesel system and a Photovoltaic (PV) battery-free irrigation system. The second system requires isolated pipes so solar radiation does not affect water temperature and avoids damage to plant roots. The 192 kW PV system was sized to operate a 60 KW water pumping system, with a required area of 1920 m2 for implementation. Direct irrigation using PV systems proved the best economical solution since it incurs the fewest costs of $0.015/m3 for 100–120 m well depth, compared with $0.073/m3 from the conventional system. As a result, the proposed PV-pumping system reduced the overall system cost by around 80% concerning the conventional system.

PENGARUH PEMBERIAN PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) PADA PERTUMBUHAN BIBIT STEK STEVIA (Stevia rebaudiana Bertoni)

Sweetleaf stevia (Stevia rebaudiana Bertoni) is one of the potential sugar-producing plants besides sugar cane which is widely used as a natural non-calorie sweetener. Propagation of stevia by shoot cuttings produces more uniform seedlings. Plant Growth Promoting Rhizobacteria (PGPR) contains a group of beneficial bacteria that live in the plant root ecosystem that can stimulate plant growth. This study aims to determine the effect of PGPR on the growth of stevia cuttings and the best concentration of PGPR on the growth of stevia cuttings. This study was conducted in February-May 2024 in Kolongan Atas II Village, Sonder District, Minahasa Regency, North Sulawesi Province. The study used a Completely Randomized Design (RAL), with 5 treatment levels, namely P0 = Control (Without PGPR), P1 = PGPR 10 ml/liter of water, P2 = PGPR 20 ml/liter of water, P3 = PGPR 30 ml/liter of water and P4 = PGPR 40 ml/liter of water. Each treatment was repeated 4 times.The results showed that the aplication of PGPR affected the growth of stevia cuttings. The best PGPR concentration for the growth of stevia cuttings was at a PGPR treatment concentration of 20 ml/liter of water. Keywords: plant growth promoting rhizobacteria, stevia

Removal of formaldehyde from indoor air by potted Sansevieria trifasciata plants: dynamic influence of physiological traits on the process

AbstractPlant-based removal of indoor formaldehyde is a widely studied method, yet little is known about the dynamic changes in this process. In this study, potted Sansevieria trifasciata Prain plants were exposed to 5-ppm formaldehyde gas concentration for 7 days. The results showed that formaldehyde exposure led to plant stress, affected photosynthesis, and damaged membrane lipids, as evidenced by a decrease in chlorophyll content, an increase in Chl a/b ratio and malondialdehyde content. However, the formaldehyde removal ability of the plants increased over the first 5 days, peaking at 18.02 mg h−1 kg−1 dry weight on the 5th day. This trend was correlated with changes in various indicators in the plant roots, including phytohormone and antioxidant enzymes. Notably, catalase activity in the roots behaved differently from other indicators. The indicators in the leaves showed turning points around the 3rd day due to the direct exposure of the leaves to formaldehyde. The relative abundance of endophytes indicated an increase in plant growth-promoting bacteria, which helped the plant cope with formaldehyde stress. The study suggests that under formaldehyde stress, plants manage active oxygen content by increasing phytohormones and regulating redox reactions. This enhances their tolerances to formaldehyde, thereby improving their ability to remove formaldehyde and aiding recovery after formaldehyde exposure. Graphical abstract