Plant Growth Research Articles

The Effects of Bioinoculants on Enhancement Growth in Nanjanagud Rasabale Tissue Culture Banana

Bio-hardening is a process where micro propagated plantlets are inoculated with suitable strains of microorganisms in order to enhance their acclimatization. Trials were taken to expose banana plantlets to useful microbes that encourage growth and mutual association during 2022 at UHS, Bagalkot. It promotes host plant growth, plant nutrient uptake, inhibits pathogen growth, reduces disease severity, enhances tolerance to environmental stress etc. In the present study, twenty treatments were imposed with different bioinoculants by two methods of application (1) powder formulation and (2) liquid formulation. Among these treatments, M1T13- VAM and fusicont significantly increased the survivability per cent (58.80%), plant height (6.46 cm), pseudo stem girth (5.42 cm), number of leaves (4.07) and leaf area (33.15 cm2). Thus, the artificial inoculation of bioinoculants through the powder formulation enhances the growth during primary hardening.

New Aspects of the Effects of Climate Change on Interactions Between Plants and Microbiomes: A Review.

One of the most talked about issues of the 21st century is climate change, as it affects not just our health but also forestry, agriculture, biodiversity, the ecosystem, and the energy supply. Greenhouse gases are the primary cause of climate change, having dramatic effects on the environment. Climate change has an impact on the function and composition of the terrestrial microbial community both directly and indirectly. Changes in the prevailing climatic conditions brought about by climate change will lead to modifications in plant physiology, root exudation, signal alteration, and the quantity, makeup, and diversity of soil microbial communities. Microbiological activity is very crucial in organic production systems due to the organic origin of microorganisms. Microbes that benefit crop plants are known as plant growth-promoting microorganisms. Thus, the effects of climate change on the environment also have an impact on the abilities of beneficial bacteria to support plant growth, health, and root colonization. In this review, we have covered the effects of temperature, precipitation, drought, and CO2 on plant-microbe interactions, as well as some physiological implications of these changes. Additionally, this paper highlights the ways in which bacteria in plants' rhizosphere react to the dominant climatic conditions in the soil environment. The goal of this study is to analyze the effects of climate change on plant-microbe interactions.

Root Endophyte-Manipulated Alteration in Rhizodeposits Stimulates Claroideoglomus in the Rhizosphere to Enhance Drought Resistance in Peanut.

Drought dramatically affects plant growth and yield. A previous study indicated that endophytic fungus Phomopsis liquidambaris can improve the drought resistance of peanuts, which is related with the root arbuscular mycorrhizal fungi (AMF) community; however, how root endophytes mediate AMF assembly to affect plant drought resistance remains unclear. Here, we explored the mechanism by which endophytic fungus recruits AMF symbiotic partners via rhizodeposits to improve host drought resistance. The results showed that Ph. liquidambaris enhanced peanut drought resistance by enriching the AMF genus Claroideoglomus of the rhizosphere. Furthermore, metabolomic analysis indicated that Ph. liquidambaris significantly promoted isoformononetin and salicylic acid (SA) synthesis in rhizodeposits, which were correlated with the increase in Claroideoglomus abundance following Ph. liquidambaris inoculation. Coinoculation experiments confirmed that isoformononetin and SA could enrich Claroideoglomus etunicatum in the rhizosphere, thereby improving the drought resistance. This study highlights the crucial role of fungal consortia in plant stress resistance.

Delivery of luminescent particles to plants for information encoding and storage.

In the era of smart agriculture, the precise labeling and recording of growth information in plants pose challenges for modern agricultural production. This study introduces strontium aluminate particles coated with H3PO4 as luminescent labels capable of spatial embedding within plants for information encoding and storage during growth. The encapsulation with H3PO4 imparts stability and enhanced luminescence to SrAl2O4:Eu2+,Dy3+ (SAO). Using SAO@H3PO4 as a low-damage luminescent label, we implement its delivery into plants through microneedles (MNs) patches. The embedded SAO@H3PO4 within plants exhibits sustained and unaltered high signal-to-noise afterglow emission, with luminous intensity remaining at approximately 78% of the original for 27 days. To cater to diverse information recording needs, MNs of various geometric shapes are designed for loading SAO@H3PO4, and the luminescent signals in different shapes can be accurately identified through a designed program, the corresponding information can be conveniently viewed on a computer. Additionally, inspired by binary information concepts, MNs patches with specific arrangements of luminescent and non-luminescent points are created, resulting in varied luminescent MNs arrays on leaves. An advanced camera system with a tailored program accurately identifies and maps the labels to the corresponding recorded information. These findings showcase the potential of low-damage luminescent labels within plants, paving the way for convenient and widespread storage of plant growth information.

Political Economic Role in Natural Quality Management and its Impact on Plant Ecology: Why Arar-Juniper Plants Disappeared

Wadi-Arar is a unique region that has lost some of its most important natural features within 200 years, including plants, geographical lakes, and valleys. The study aimed to investigate the disappearance of the juniper plant, a vital species in Saudi Arabia, in recent decades. The research highlighted various factors influencing the quality of life for the juniper plant and its habitats. It sought to identify the primary factors causing changes in the natural conditions of the plant and those influencing its growth. The findings indicated a significant impact of the Suez Canal on the Arar region, the sole connection between Africa and Asia, and Europe. This influence extends beyond geopolitical factors in the surrounding area, as the existence of the Suez Canal disrupted the natural life cycle of many animal species over thousands of years of migrations and coexistence across Earth's continents. These animals previously provided natural organic fertilizer to the soil, supporting plant growth. However, due to low rainfall resulting in low natural nutrients and high salinity, the plants' viability has diminished, reflecting a history of administrative and geopolitical decisions.

Response of seed germination, seedling growth and physiological characteristics to alkali stress in halophyte Suaeda liaotungensis.

Soil salinization has been considered as a major environmental threat to plant growth. Different types of salt in saline soil have different effects on germination and seedling growth. Effect of NaCl on germination and seedling establishment in Suaeda liaotungensis have been reported, but its response to alkali stress remains unclear. Our results showed that brown seeds had higher germination rate, however, black seeds had higher germination recovery percentage under alkali stress. Na2CO3 had stronger inhibitory effect on germination and seedling growth than NaHCO3. As the concentration of alkali stress increased, the ROS level of brown seeds gradually ascended, while that of black seeds decreased first and then ascended. MDA content of dimorphic seeds significantly increased under alkali stress. The trend of SOD, POD and CAT activity between dimorphic seeds was similar under the same type of alkali stress. Alkali stress enhanced proline content of dimorphic seeds, and dimorphic seeds in NaHCO3 solution had higher proline content than Na2CO3 solution. Moreover, radicle and shoot tolerance indexes of seedlings in NaHCO3 solution were significantly higher than that of Na2CO3 solution. Under strong alkali stress, seedlings in NaHCO3 solution had significantly lower ROS level and MDA content as well as higher antioxidant enzyme activity than Na2CO3 solution. This study comprehensively compared the morphological and physiological characteristics in germination and seedlings to better reveal the saline-alkali tolerance mechanisms in S. liaotungensis.

Genome-wide identification and characterization of SLEEPER, a transposon-derived gene family and their expression pattern in Brassica napus L.

The transposons of the hAT superfamily are the most widespread transposons ever known. SLEEPER genes encode domesticated transposases from the hAT superfamily, which may have lost their transposable functions during long-term evolution and transformed into host proteins that regulate plant growth and development. This study identified 162 members of the SLEEPER gene family from Brassica napus. These members are widely distributed on 19 chromosomes, mainly in the Cn subgenome, and have promoters with various cis-acting elements related to hormone regulation, abiotic stress, and growth and development regulation. Most of the genes in this family contain similar conserved domains and motifs, and the closer the genes are distributed on evolutionary branches, the more similar their structures are. Transcriptome sequencing performed on tissues at different growth stages from B. napus line 3529 indicated that these genes had different expression patterns, and nearly half of the genes were not detectably expressed in all samples. This study investigated the gene structure, expression patterns, evolutionary features, and gene localization of the SLEEPER family members to confirm the significance of these genes in the growth of B. napus, providing a reference for the study of transposon domestication and outstanding genetic resources for the genetic improvement of B. napus.

Impact of Bio-Organic Fertilizer Incorporation on Soil Nutrients, Enzymatic Activity, and Microbial Community in Wheat–Maize Rotation System

Excessive use of inorganic fertilizers disrupts soil nutrient balance and leads to soil degradation and a decrease in biodiversity. In contrast, bio-fertilizers enhance soil structure and fertility and promote plant growth and sustainable agriculture development. Therefore, this study focused on a rotation system of winter wheat and summer maize and aimed to explore the effects of applying chemical fertilizer (NPK) and bio-fertilizer (BF) in the winter wheat season on the sustainable soil development of current wheat and subsequent maize. Before sowing winter wheat four fertilization treatments were, respectively CK (100% NPK at 750 kg ha−1), A (60% NPK at 450 + 20% BF at 150 kg ha−1), B (60% NPK at 450 + 40% BF at 300 kg ha−1), and C (60% NPK at 450 + 60% BF at 450 kg ha−1), conducted. The results showed that treatment A (60% NPK + 20% BF) replacing the NPK at 300 kg ha−1 with BF at 150 kg ha−1 significantly soil nutrient contents, enzyme activity, and microbial metabolic activity. The study also found a positive correlation between soil parameters (total nitrogen, alkaline nitrogen, available phosphorus, organic matter, urease, and alkaline phosphatase in the winter wheat and maize cropping season). Furthermore, the soil microbial composition showed significant enrichment of Proteobacteria, Acidobacteria, Actinobacteria, and Firmicutes, and variations among treatments. Moreover, the application of biofertilizer enhanced the diversity of soil fungi species, particularly during the winter wheat season. This study highlights the importance of integrating biofertilizers with NPK fertilizer for agricultural system conversion and promoting agricultural production and sustainability.

Review of current hydroponic food production practices and the potential role of bioelectrochemical systems

AbstractHydroponic cultivation is an efficient, resource-saving technology that produces high yields of high-quality products per unit area without soil. While this technology can save water and fertilisers, water recirculation increases the accumulation of root exudates known to be toxic to the plant, causing growth inhibition. The usage of bioelectrochemical systems (BESs) is well-documented for wastewater treatment, desalination, contamination remediation, bioelectricity generation, etc. In this review we explore the issues associated with the usage of traditional approaches in detecting and removing the phytotoxic substances exudated from plant roots. Furthermore, we investigate the prospects of deploying BESs in hydroponic systems and highlight potential benefits and challenges. The application, feasibility and scalability of BES-hydroponic systems, as well as the possibility of integration with other technologies are all critically discussed. It is concluded that the use of BESs for hydroponic wastewater treatment and for real-time plant growth monitoring represents a novel and valuable strategy. This approach has the potential to overcome limitations of the existing treatment methods and contribute to the advancement of sustainable agriculture. Graphical abstract

The B-box transcription factor BnBBX22.A07 enhances salt stress tolerance by indirectly activating BnWRKY33.C03.

Salt stress has a detrimental impact on both plant growth and global crop yields. B-box proteins have emerged as pivotal players in plant growth and development regulation. Although the precise role of B-box proteins orchestrating salt stress responses in B. napus (Brassica napus) is not well understood in the current literature, further research and molecular explorations are required. Here, we isolated the B-box protein BnBBX22.A07 from B. napus. The overexpression of BnBBX22.A07 significantly improved the salt tolerance of Arabidopsis (Arabidopsis thaliana) and B. napus. Transcriptomic and histological analysis showed that BnBBX22.A07 enhanced the salt tolerance of B. napus by activating the expression of reactive oxygen species (ROS) scavenging-related genes and decreasing salt-induced superoxide anions and hydrogen peroxide. Moreover, BnBBX22.A07 interacted with BnHY5.C09, which specifically bound to and activated the promoter of BnWRKY33.C03. The presence of BnBBX22.A07 enhanced the activation of BnHY5.C09 on BnWRKY33.C03. Overexpression of BnHY5.C09 and BnWRKY33.C03 improved the salt tolerance of Arabidopsis. Functional analyses revealed that BnBBX22.A07-mediated salt tolerance was partly dependent on WRKY33. Taken together, we demonstrate that BnBBX22.A07 functions positively in salt responses not only by activating ROS scavenging-related genes but also by indirectly activating BnWRKY33.C03. Notably, our study offers a promising avenue for the identification of candidate genes that could be harnessed in breeding endeavours to develop salt-resistant transgenic crops.

Tithonia diversifolia (Asteraceae) as a reservoir of natural enemies to promote pest control and improve development of tomato (Solanum lycopersicum) in open conditions

ABSTRACT Tithonia diversifolia has the potential for use as a reservoir for entomophages in pest control, as it attracts and preserves natural enemies before migrating to the target crop, where a high incidence of pests occurs. For example, in tomato crop production one of the limiting factors, under field condition, is the incidence of phytophagous insects. We determined the effects of Tithonia diversifolia on species assemblage structure of natural enemies and pest insects (abundance and diversity), plant growth (leaf area, stem length and diameter, number of leaves, flowers and fruits, and fruits weight/per plant), plant defense (leaf thickness and hardness) and fruit colouration on tomato plants in open conditions. Through direct and indirect samplings, a total of 456 insects were collected, comprising 76 natural enemies, 269 pests and 111 belonging other guilds. Length, stem diameter, number of flowers, leaf thickness, and hardness increased, while the number of leaves decreased. T. diversifolia plants increased natural enemies but not pest abundance in tomato plants, demonstrating that this plant can alter the structure of the insect community associated with tomato.

Enhancing saffron (Crocus sativus L.) growth in the Kashmir valley with resilient and widely effective Plant Growth-Promoting Rhizobacteria (PGPR) under field conditions

This study provides a thorough examination of stress-tolerant plant growth-promoting rhizobacteria (PGPR) and their significance in enhancing plant growth and biocontrol activities, and influence on saffron cultivation in the Kashmir Valley. Quantitative analysis of 35 efficient PGPR revealed significant variability in plant growth promotion (PGP) attributes ranging from 60 to 653 µg/ml tri-calcium phosphate (TCP) solubilization, 1548–4311 nM α-ketobutyrate h/mg/protein ACC-deaminase activity, 1.4–74.8 µg/ml IAA-like auxins production, and 94–214 % siderophore production. Molecular fingerprinting disclosed 52 ERIC types that belonged to 25 genera, mainly Bacillus. Bacillus species including B. aryabhattai, B. halotolerans, B. methylotrophicus, B. safensis, B. siamensis and B. simplex dominated the PGPR population, along with Pseudomonas spp., such as P. azotoformans and P. chlororaphis, indicating a selective buildup of PGPR in the saffron rhizosphere. In-vivo and In-vitro dual inoculation test of these widespread PGPR and stress-tolerant also inhibited the mycelial growth of Fusarium species including F. oxysporum, F. oxysporum f. sp. ciceris, and F. proliferatum. The field application of seven selected PGPR strains resulted in significant improvements in saffron productivity, including increased sprouted corms, plant height, stigma length, and stigma fresh and dry weight, which ranged from 0.6-1.8 %, 0.4–0.7 %, 0.3–0.5 %, and 6–19 %, respectively. These strains have the potential to stimulate cormlet growth and ultimately increase saffron production. Therefore, the PGP traits of these stress-tolerant rhizobacteria contributing to nutrients solubilization, auxin biosynthesis, and fungicidal attributes can ameliorate the saffron agricultural practices.

Trends in Greenhouse Production Technology with Special Reference to Protected Cultivation of Horticultural Crops

Greenhouse is an important application scenario of modern agriculture. With the improvement of people's life quality, the demand for vegetables, fruits, flowers and has also increased, and the amount of greenhouses has developed rapidly. Greenhouse adopts artificial technical means to change natural light and temperature conditions, and to create environmental factors to optimize the growth of animals and plants, so that greenhouse crops can grow throughout the year and the weather. Compared with traditional planting methods, the greenhouse is more automated, intelligent, and mechanized. Greenhouse farming (Protected cultivation) refers to the practice of growing crops in an enclosed or partially enclosed environment, such as greenhouses, shade houses, or high tunnels. The primary purpose of protected cultivation is to create a controlled microclimate that shields the crops from adverse weather conditions, pests, and diseases, while optimizing environmental factors. It involves the use of structures, materials, and technologies that provide a protective barrier and allow for manipulation of temperature, humidity, light, and other environmental variables. The benefits of greenhouses are high production per unit area because the genetic potential of the crop can be completely exploited, vegetables and nurseries can be grown off-season that obtain high market prices, good quality products and it is easy to protect the crops from pests, diseases and extreme climatic conditions. Greenhouse farming is a highly intensive industry that needs considerable labour and capital inputs. Because of this, all factors important for a successful enterprisers should be carefully considered by potential growers.

Identification of autophagy-related genes ATG18 subfamily genes in potato (Solanum tuberosum L.) and the role of StATG18a gene in heat stress

Autophagy is a highly conserved process in eukaryotes that is used to recycle the cellular components from the cytoplasm. It plays a crucial function in responding to both biotic and abiotic stress, as well as in the growth and development of plants. Autophagy-related genes (ATG) and their functions have been identified in numerous crop species. However, their specific tasks in potatoes (Solanum tuberosum L.), are still not well understood. This work is the first to identify and characterize the potato StATG18 subfamily gene at the whole-genome level, resulting in a total of 6 potential StATG18 subfamily genes. We analyzed the phylogenetic relationships, chromosome distribution and gene replication, conserved motifs and gene structure, interspecific collinearity relationship, and cis-regulatory elements of the ATG18 subfamily members using bioinformatics approaches. Furthermore, the quantitative real-time polymerase chain reaction (qRT-PCR) analysis suggested that StATG18 subfamily genes exhibit differential expression in various tissues and organs of potato plants. When exposed to heat stress, their expression pattern was observed in the root, stem, and leaf. Based on a higher expression profile, the StATG18a gene was further analyzed under heat stress in potatoes. The subcellular localization analysis of StATG18a revealed its presence in both the cytoplasm and nucleus. In addition, StATG18a altered the growth indicators, physiological characteristics, and photosynthesis of potato plants under heat stresses. In conclusion, this work offers a thorough assessment of StATG18 subfamily genes and provides essential recommendations for additional functional investigation of autophagy-associated genes in potato plants. Moreover, these results also contribute to our understanding of the potential mechanism and functional validation of the StATG18a gene’s persistent tolerance to heat stress in potato plants.

Manure-derived black soldier fly frass enhanced the growth of chilli plants (Capsicum annuum L.) and altered rhizosphere bacterial community

Sustainable manure management is crucial for minimising environmental impacts as the livestock industry expands to meet the increasing demand for protein. Black soldier fly (Hermetia illucens L.) larvae (BSFL) farming is an emerging waste management method that efficiently processes large volumes of organic waste, including manure, to produce valuable protein, oil and chitin products. Frass, a nutrient-rich by-product of black soldier fly farming, has potential as an organic fertiliser. However, research has primarily focused on frass derived from food waste, with little exploration of manure-derived BSFL frass. This study aimed to determine whether frass derived from manure could enhance the growth of chilli (Capsicum annuum L.) over 14 weeks under controlled glasshouse conditions. The impacts of manure-derived BSFL frass on soil properties and soil bacterial communities were characterised. The results indicated that a 0.6 % w/w application rate yielded the highest chilli plant biomass, with reduced growth observed at higher rates. The enhanced growth at optimal manure-derived BSFL frass application rates was due to increased nitrogen content, whereas reduced growth at higher rates was likely caused by phytotoxicity from not completely decomposed frass. Soil microbial biomass carbon and nitrogen also increased with manure-derived BSFL frass, implying microbial carbon and nitrogen immobilisation. Additionally, the changes in pH and nutrients due to manure-derived BSFL frass caused shifts in the bacterial community in the chilli plant rhizosphere, enriching the relative abundance of bacteria with potential growth-promoting properties. This study highlights the potential of integrating manure into black soldier fly waste management processes, demonstrating that manure-derived BSFL frass can be used as an organic fertiliser with circular economy benefits.

A circadian clock output functions independently of phyB to sustain daytime PIF3 degradation.

The circadian clock is an endogenous oscillator, and its importance lies in its ability to impart rhythmicity on downstream biological processes, or outputs. Our knowledge of output regulation, however, is often limited to an understanding of transcriptional connections between the clock and outputs. For instance, the clock is linked to plant growth through the gating of photoreceptors via rhythmic transcription of the nodal growth regulators, PHYTOCHROME-INTERACTING FACTORs (PIFs), but the clock's role in PIF protein stability is less clear. Here, we identified a clock-regulated, F-box type E3 ubiquitin ligase, CLOCK-REGULATED F-BOX WITH A LONG HYPOCOTYL 1 (CFH1), that specifically interacts with and degrades PIF3 during the daytime. Additionally, genetic evidence indicates that CFH1 functions primarily in monochromatic red light, yet CFH1 confers PIF3 degradation independent of the prominent red-light photoreceptor phytochrome B (phyB). This work reveals a clock-mediated growth regulation mechanism in which circadian expression of CFH1 promotes sustained, daytime PIF3 degradation in parallel with phyB signaling.

Homeodomain leucine zipper (HD-ZIP) gene family in Apostasia shenzhenica Z. J. Liu & L. J. Chen (Orchidaceae): In silico identification and characterization

The homeodomain leucine zipper (HD-ZIP) gene family constitutes an important class of transcription factors found in plants that play crucial roles in various aspects of growth, development and stress regulation. Despite this, there have been minuscule reports on identification and characterization of HD-ZIP gene family in orchids. The present study identifies 31 putative genes (AsHD-ZIP) in Apostasia shenzhenica, using in silico approaches. All of the identified transcription factors were grouped into four subfamilies (HD-ZIP I to IV) based on the distribution of various conserved domains and motifs i.e., HD-ZIP I (homeodomain and leucine zipper), HD-ZIP II (homeodomain, leucine zipper and CPSCE), HD-ZIP III (homeodomain, leucine zipper, MEKHLA and START) and HD-ZIP IV (homeodomain, leucine zipper and START). Prediction of physicochemical properties, protein structures, protein-protein interactions, gene ontology, and gene structures further validated this classification. Phylogenetic analysis showed clustering of all subgroups separately along with their orthologs in Arabidopsis thaliana, Oryza sativa, Dendrobium catenatum and Phalaenopsis equestris. Furthermore, spatio-temporal expression profiling and presence of cis-regulatory elements confirmed tissue specific expression. As HD-ZIP genes are vital players in regulation of plant growth and development as well as in biotic and abiotic stress responses, this study provides a foundation for genetic improvement in orchids through functional validation and characterization of HD-ZIP gene family.

Soil health is associated with higher primary productivity across Europe.

Soil health is expected to be of key importance for plant growth and ecosystem functioning. However, whether soil health is linked to primary productivity across environmental gradients and land-use types remains poorly understood. To address this gap, we conducted a pan-European field study including 588 sites from 27 countries to investigate the link between soil health and primary productivity across three major land-use types: woodlands, grasslands and croplands. We found that mean soil health (a composite index based on soil properties, biodiversity and plant disease control) in woodlands was 31.4% higher than in grasslands and 76.1% higher than in croplands. Soil health was positively linked to cropland and grassland productivity at the continental scale, whereas climate best explained woodland productivity. Among microbial diversity indicators, we observed a positive association between the richness of Acidobacteria, Firmicutes and Proteobacteria and primary productivity. Among microbial functional groups, we found that primary productivity in croplands and grasslands was positively related to nitrogen-fixing bacteria and mycorrhizal fungi and negatively related to plant pathogens. Together, our results point to the importance of soil biodiversity and soil health for maintaining primary productivity across contrasting land-use types.

Plant growth promoting endophyte modulates soil ecological characteristics during the enhancement process of cadmium phytoremediation

Endophyte assisted phytoremediation of cadmium (Cd) contaminated soil represents a promising strategy. However, the precise soil ecological regulatory mechanisms by which endophyte enhance the Cd phytoextraction remain unclear. Here, we employed the plant growth promoting endophyte (PGPE) Pseudomonas sp. E3, which has been validated to effectively enhance Cd extraction in Solanum nigrum L., to investigate its regulatory mechanism on soil ecology. The results demonstrated that while PGPE inoculation resulted in minimal alterations to the physicochemical properties of the bulk soil, it led to a notable increase in acid phosphatase activity by 17.86% and urease activity by 24.85% in the rhizosphere soil. This, in turn, significantly raised the available nitrogen and phosphorus contents by 16.93% and 21.27%, respectively, in the rhizosphere soil. Additionally, PGPE inoculation effectively replenished the bioavailable fractions of Fe and Cd, which had been depleted due to root uptake. Importantly, the inoculation specifically augmented the abundance of biomarkers p_Patescibacteria, f_Saccharimonadales, and g_Saccharimonadales in the rhizosphere soil. These biomarkers exhibited a significant positive correlation with the available nutrient and metal element contents. Moreover, the co-occurrence network analysis demonstrated that the inoculation resulted in a simplified bacterial community network, which may have facilitated community synergism by displacing bacteria with a negative association. This regulation appears to occur independently of PGPE colonization. Overall, our findings suggested that PGPE also exerts a regulatory influence on soil ecological features, significantly aiding hyperaccumulators in nutrient acquisition and heavy metal accumulation.

Physicochemical and Biological Changes of Compost Inoculated with Pseudomonas Aeruginosa AAC1 and Rock Phosphate: Implications for P Availability

Phosphorus (P) is an essential nutrient for plant growth, but its availability in soil is often limited. Present study was conducted to design compost enriched with phosphate-solubilizing bacteria (PSB) and rock phosphate (RP). Four compost piles were prepared with RP and 30:1 carbon-to-nitrogen (C: N). Out of these, two piles were inoculated with PSB strain Pseudomonas aeruginosa AAC1 (RP + AAC1) while two piles were left un-inoculated and served as control (RP). The physicochemical assessment of the designed compost revealed that the addition of RP and inoculation of P. aeruginosa AAC1 (RP + AAC1) significantly (p < 0.05) increased the composting temperature (over 58 °C), calcium (36.84%), magnesium (35%) and available P contents (43.50%) indicating the solubilization of inorganic P, Ca and Mg bound phosphates However, the addition did not significantly (p > 0.05) influence the carbon (C), carbon to nitrogen (C/N) ratio, organic matter, and ash content but significantly (p < 0.05) reduced the moisture content (41%) and pH (up to 5.4). After 60 days, all compost piles reached maturity at temperature ranges of 27-30 °C, pH level between 7.2–7.6, and moisture content 31-35%. Scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM-EDS) confirmed the presence of elements including carbon (C), oxygen (O), magnesium (Mg), aluminum (Al), silicon (Si), calcium (Ca), and P (P) in the compost. Microbiological monitoring revealed the survival of P. aeruginosa AAC1 during the composting process even at higher temperatures (∼58 °C). Indigenous bacterial populations were recovered within the range of 109 - 1014 CFUg−1. Compost was also safe in regard to heavy metal concentrations. Thus, the results suggest that combining P. aeruginosa AAC1 and RP in compost can enhance the availability of soluble P, thus serving as an effective phosphatic biofertilizer.