Haematococcus pluvialis bionanoparticles boost maize seedling health, serving as a sustainable seed priming agent and biostimulant for agriculture

The rising frequency of extreme climate events requires sustainable strategies to secure food production. Environmental stress impacts seed germination and seedling development, posing a significant agricultural challenge. To address this, we developed and applied iron-based nanoparticles (Bio-NPs) synthesized through green biosynthesis from Haematococcus pluvialis, a microalga rich in antioxidants like astaxanthin. These Bio-NPs, approximately 21 nm in diameter and characterized by a negative surface charge, were used as priming agents for maize seeds. Their effects on physiological traits were analyzed with multispectral imaging, showing enhanced normalized difference vegetation index (NDVI) and chlorophyll levels in maize seedlings, highlighting Bio-NPs as effective biostimulants. Among the tested concentrations, 6 mM Bio-NPs yielded the most substantial improvements in seedling health compared to unprimed and hydro-primed groups. Importantly, in vitro studies confirmed that Bio-NPs had no harmful effects on beneficial bacteria and fungi of agronomic importance, underscoring their safety. Although the exact biological pathways responsible for these enhancements are yet to be fully understood, further research into plant responses to Bio-NPs could yield new insights into plant biostimulation. Bio-NPs thus hold promises for strengthening seedling resilience under extreme environmental scenarios, currently observed due to global climate change, offering a safe, sustainable approach to agricultural enhancement. By leveraging microalgae-based biostimulants, this work advances seed priming technology, fostering crop resilience and supporting environmentally friendly agricultural practices.

Seeds of Change: exploring the transformative effects of seed priming in sustainable agriculture

The threats posed by climate change on agriculture at a global scale have fostered researchers to explore new and efficient strategies to ensure stable and safe food production. These new strategies must not only be efficient in reducing yield loss but also comply with environmental and consumer safety regulations, which particularly refer to restrictions to pesticide application as well as the implementation of genetically modified organisms, including CRISPR/Cas edited lines. Among other approaches, priming constitutes an easier and relatively cheaper strategy to cope with the effects of abiotic and biotic stresses by boosting plants' endogenous potential. Particularly, pre-sowing seed priming has proven effective in improving germination and seedling establishment as well as tolerance to environmental and biotic factors throughout the plant's life cycle, exhibiting clear long-lasting effects. This tolerance response to a wide range of adverse factors is associated with physiological, metabolic and genetic mechanisms and responses at the seed level and subsequently in the established plant. The genetic and epigenetic mechanisms enabling this tolerance response in plants and their subsequent generation, as a transgenerational effect, will be reviewed. Finally, the potential of the different seed priming approaches contributing to an ecologically and economically more sustainable agriculture will be discussed.

Transcriptional mechanisms underlying thiazolidine-4-carboxylic acid (T4C)-primed salt tolerance in Arabidopsis

KEY MESSAGE

T4C enhances salt stress tolerance in Arabidopsis by regulating osmotic and oxidative stress responses, activating ABA-related pathways, and inducing stress-responsive genes, including LEA proteins. High soil salinity is a major environmental stress that restricts crop productivity worldwide, necessitating strategies to enhance plant salt tolerance. Thiazolidine-4-carboxylic acid (T4C) has been reported to regulate proline biosynthesis, which is essential for abiotic stress responses, yet its role in stress tolerance remains unclear. This study investigates the physiological and molecular effects of T4C on Arabidopsis thaliana under salt stress conditions. T4C treatment alleviated salt-induced growth inhibition, improving biomass, relative water content, and chlorophyll retention while reducing oxidative stress markers such as malondialdehyde and anthocyanin accumulation. Transcriptomic and quantitative PCR analyses revealed that T4C upregulated proline biosynthesis genes, ABA-dependent signaling (RD29b, ABI3), and Late Embryogenesis Abundant (LEA) genes. Gene Ontology (GO) enrichment analysis identified biological processes related to water deprivation, ABA signaling, and salt stress, while Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated the involvement of phenylpropanoid biosynthesis, plant hormone signal transduction, and MAPK signaling in T4C-mediated responses. Notably, several transcription factors, including NAC, MYB, and WRKY family members, were identified as candidates involved in T4C-mediated stress priming. Collectively, these findings suggest that T4C may enhance salt tolerance by modulating osmotic balance, reducing oxidative stress, and activating stress-responsive genes and transcriptional regulators. Our results provide novel insights into the molecular mechanisms underlying T4C-mediated stress responses, highlighting its potential as a chemical priming agent to improve plant resilience under saline conditions.

How to improve the potential of microalgal biostimulants for abiotic stress mitigation in plants?

Abiotic stress is among the most critical factors limiting crop productivity worldwide and its importance is further exacerbated by climate change. In recent years, microalgal biostimulants have gained attention for their potential to enhance plant resilience towards abiotic stress. However, significant hurdles still persist, particularly regarding the unknown modes of action of microalgal biostimulants, which is a concern for stringent regulatory requirements and product reliability. The aim of this review is to improve the potential of microalgal biostimulants for abiotic stress mitigation in plants by addressing different key parameters shaping the efficacy of microalgal biostimulants, encompassing cultivation approaches, extraction techniques, and application methods. Furthermore, it also highlights how microalgal biostimulants modulate plant morphology, physiology and biochemistry under drought, salinity, and heat stress-three predominant stressors anticipated to intensify under climate change. Notably, these biostimulants consistently enhance drought stress tolerance by improving biomass accumulation, nutrient uptake, and water use efficiency through enhanced photosynthesis and stomatal regulation. These effects are largely driven by the accumulation of osmoprotectants and antioxidant compounds. In contrast, salt stress mitigation is highly species-dependent, with some microalgae enhancing stress tolerance through osmoprotectant and antioxidant accumulation, while others reduce these compounds, potentially lowering stress perception via unknown mechanisms. Despite the significance of the abiotic stress, heat stress mitigation by microalgal biostimulants remains an underexplored research area. Additionally, indirect applications of microalgae-ranging from biotechnological innovations to desalination-underscore the broader potential of these organisms in agricultural resilience. Collectively, this review identifies three key gaps in the existing literature-the diversity gap, the practical gap, and the research gap-while outlining promising avenues for future research in microalgal biostimulant development.

Advances in using non-thermal plasmas for healthier crop production: toward pesticide and chemical fertilizer-free agriculture

MAIN CONCLUSION

There is an urgent need for sustainable agriculture. Non-thermal plasma seed treatment offers a promising alternative by enhancing germination, nutrient uptake, and disease resistance, and reducing reliance on pesticides and fertilizers. There is an urgent need to transform agricultural practices to meet the challenges of sustainable food production amidst global population growth and environmental degradation. Traditional crop production methods heavily rely on pesticides and synthetic fertilizers, which pose significant risks to human health, disrupt ecosystems, and contribute to environmental pollution. Moreover, these methods are increasingly unsustainable due to rising costs and diminishing effectiveness, evolving pest resistance, and climate change impacts. Recently, non-thermal plasma (NTP) technology has emerged as a promising alternative for seed treatment in agriculture. NTP uses low-temperature plasma to modify seed surfaces, enhancing germination, vigor, and overall plant growth. Studies have demonstrated that NTP treatment improves nutrient uptake, increases disease resistance, and reduces the reliance on chemical inputs (pesticides and fertilizers), thereby promoting pesticide and chemical fertilizer-free agriculture. This paper explores recent research advancements in NTP seed treatment and its potential applications in sustainable agriculture. By exploring the mechanisms underlying the NTP effects on seed physiology, the paper provides a comprehensive understanding of how this technology can contribute to sustainable crop production. Furthermore, the paper discusses the strengths, weaknesses, opportunities, and challenges associated with the potential large-scale use of low-temperature plasmas in agriculture, aiming to accelerate the adoption of NTP and its commercialization in the agro-food industries. Overall, the goal of this paper is to highlight the transformative potential of NTP seed treatment in achieving healthier crop production that is environmentally friendly, economically viable, and capable of meeting the food demands of a growing global population.

Chemical Seed Priming: Molecules and Mechanisms for Enhancing Plant Germination, Growth, and Stress Tolerance

Food security is one of the world's top challenges, specifically considering global issues like climate change. Seed priming is one strategy to improve crop production, typically via increased germination, yields, and/or stress tolerance. Hydropriming, or soaking seeds in water only, is the simplest form of seed priming. However, the addition of certain seed priming agents has resulted in a variety of modified strategies, including osmopriming, halopriming, hormonal priming, PGR priming, nutripriming, and others. Most current research has focused on hormonal and nutripriming. This review will focus on the specific compounds that have been used most often over the past 3 years and the physiological effects that they have had on crops. Over half of recent research has focused on four compounds: (1) salicylic acid, (2) zinc, (3) gibberellic acid, and (4) potassium nitrate. One of the most interesting characteristics of all chemical seed priming agents is that they are exposed only to seeds yet confer benefits throughout plant development. In some cases, such benefits have been passed to subsequent generations, suggesting an epigenetic effect, which is supported by observed changes in DNA methylation and histone modification. This review will summarize the current state of knowledge on molecular changes and physiological mechanisms associated with chemical seed priming agents and discuss avenues for future research.

Plant growth promotion via priming with volatile organic compounds emitted from Bacillus vallismortis strain EXTN-1

Volatile organic compounds (VOCs) produced by potential plant growth-promoting rhizobacteria (PGPR) play an important role in plant interactions. However, the mechanisms underlying this phenomenon are not well understood. Our findings show that the influence of VOCs from the PGPR strain Bacillus vallismortis (EXTN-1) on tobacco plant growth is dependent on the culture media used. The VOCs released from sugar-rich media such as potato dextrose agar (PDA) and King's B (KB) media were highly effective. However, exposure to VOCs from nutrient agar (NA), tryptic soy agar (TSA), and Luria-Bertani (LB) resulted in chlorosis and stunted plant growth. This effect was caused by the discharge of a large amount of ammonia that altered the pH of the plant growth media. Seedlings exposed to VOCs for 10 days exhibited improved growth even after the VOCs were eliminated under greenhouse conditions. Priming of seeds with VOCs for 24 and 48 h induced higher growth than the untreated control, and seeds with 48 h exposure were better as compared to 24 h treatment. Chemical characterization of VOCs emitted by EXTN-1 in different media using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) showed the presence of 2,3-butanedione and monoxime in all spectra. However, 1-butanol was the prominent peak in VOC of EXTN-1 grown in KB and NA, while acetoin was highest in PDA, followed by KB. Heneicosane and benzaldehyde were exclusively produced in NA media, and these synthetic compounds improved growth in the I-plate assay. This work indicates that VOCs released from EXTN-1 are important for the growth-promoting effect of EXTN-1.

Salicylic acid priming before cadmium exposure increases wheat growth but does not uniformly reverse cadmium effects on membrane glycerolipids

Cadmium (Cd) is an abiotic stressor negatively affecting plant growth and reducing crop productivity. The effects of Cd (25 μM) and of pre-soaking seeds with salicylic acid (SA) (500 μM) on morphological, physiological, and glycerolipid changes in two cultivars of wheat (Triticum aestivum L. 'Tosunbey' and 'Cumhuriyet') were explored. Parameters measured were length, fresh and dry biomass, Cd concentration, osmotic potential (ψ), lipid peroxidation, and polar lipid species in roots and leaves, as well as leaf chlorophyll a, carotenoids, and fv/fm. Fresh biomass of roots and leaves and leaf length were strongly depressed by Cd treatment compared to the control, but significantly increased with SA + Cd compared to Cd alone. Cd reduced leaf levels of chlorophyll a, carotenoids, and fv/fm, compared to controls. Treatment with SA + Cd increased pigment levels and fv/fm compared to Cd alone. Cd treatment led to a decrease in DW of total membrane lipids in leaves and depressed levels of monogalactosyldiacylglycerol and phosphatidic acid in leaves and roots of both cultivars. The effects of SA priming and SA + Cd treatment on lipid content and composition were cultivar-specific, suggesting that lipid metabolism may not be a primary target underlying SA remediation of the damaging effects of Cd on wheat growth and development.

Effect of Seed Hydropriming on the Elongation of Plumule and Radicle During the Germination Process and Changes in Enzyme Activity Under Water-Deficient Conditions

Hydropriming rice seeds effectively improve the germination percentage, shortens the germination period, and promotes seedling growth. The impact of seed hydropriming is to speed up growth under dry soil conditions, thereby avoiding drought damage. This study analyzes the effect of hydropriming on morpho-physiological changes in the water uptake of rice seeds using "Kasalath" and "Nipponbare" under water-deficit conditions. Upon exposure to osmotic stress, both varieties showed delays in the time to reach germination. In addition, all germination phases exhibited reductions in the activity of alpha-amylase and total soluble sugar by osmotic stress; however, in all germination phases of the hydroprimed seeds, the activity and contents of those were significantly increased, resulting in increased size of the coleoptile, plumule, and radicle. In hydroprimed seeds, "Kasalath" was superior to "Nipponbare" in the ratio of the water-deficit-to-well-watered conditions for all traits related to germination, which may have been attributable to hydropriming having a greater effect on "Kasalath". Interestingly, Primed "Kasalath" had a lower level of α-amylase, despite the having a higher content of total soluble sugars than primed "Nipponbare".

Carbon Nanomaterials in Seed Priming: Current Possibilities

The prevailing agricultural system has become deeply ingrained and insufficient due to outdated practices inherited from the Green Revolution, necessitating innovative approaches for sustainable agricultural development. Nanomaterials possess the potential to significantly improve the efficient utilization of resources while simultaneously encouraging sustainability. Among these, carbonaceous nanomaterials have found diverse applications in agriculture, exhibiting remarkable capabilities in this domain. Notably, using biowaste to produce these materials makes them both cost-effective and environmentally friendly for seed priming. Seed priming is a technique that can potentially enhance germination rates and stress tolerance by effectively regulating gene pathways and metabolism. This review provides a comprehensive summary of recent progress in the field, highlighting the challenges and opportunities of applying carbonaceous materials in seed priming to advance sustainable agriculture practices. The existing reviews provide a general overview of using carbonaceous materials (graphene and derivatives) in agriculture. Yet, they often lack a comprehensive examination of their specific application in seed-related contexts. In this review, we aim to offer a detailed analysis of the application of carbonaceous materials in seed priming and elucidate their influence on germination. Furthermore, the review shows that crop response to carbonaceous nanomaterials is linked to material concentration and crop species.

Seed priming enhances seed germination and plant growth in four neglected cultivars of Capsicum annuum L

Priming is basically a water-based technique inducing controlled seed rehydration to trigger the metabolic processes normally activated during the early phase of germination. It is regarded as an ecofriendly approach alternative to fertilizers in traditional agriculture, but also a method to synchronize off-field crops and resume stored seeds, improving vigor, and allowing for a rapid, uniform seedling emergence. In this work we tested several methods of seed priming (i.e., hydro-priming, halopriming by KNO3, and acid priming with HCl) in four ancient and neglected cultivars of Capsicum annuum L., a crop species belonging to Solanaceae family cultivated worldwide. We followed germination performance, seedling growth and selected morphological traits, antioxidant production in the leaves, and protein content of the seeds. Apart from acid priming, which inhibited root emergence, both hydropriming and halopriming decreased the mean germination time in all cultivars. The best treatments were KNO3 6% for 96 h > KNO3 4% for 48 h > hydropriming for 24 h. In particular, KNO3 6% for 96 h in all four cultivars significantly increased plant growth, simple vigor index, development germination index, leaf antioxidant concentration and protein content in the seeds, in comparison to control and other priming treatments, indicating the prompt activation of pre-germinative processes.

Small molecule, big impacts: Nano-nutrients for sustainable agriculture and food security

Human existence and the long-term viability of society depend on agriculture. Overuse of synthetic fertilizers results in increased contamination of the land, water, and atmosphere as well as financial constraints. In today's modern agriculture, environmentally friendly technology is becoming more and more significant as a substitute for conventional fertilizers and chemical pesticides. Using nanotechnology, agricultural output can be improved in terms of quality, biological support, financial stability, and environmental safety. There is a lot of promise for the sustainable application of nano-fertilizers in crop productivity and soil fertility, with little or no negative environmental effects. In this context, the present review provided an overview of the benefits of using nanofertilizers, its application and types. Mechanistic approach for increasing soil fertility and yield via nanofertilizers also described in detail. We concluded this article to compare the advantages of nanofertilizers over chemicals and nano-chemicals. Nonetheless, additional investigation is required to comprehend the effects and possible hazards of nanomaterials in the food production chain.

Identification of the Novel Small Compound Stress Response Regulators 1 and 2 That Affect Plant Abiotic Stress Signaling

Abiotic stresses, such as drought, salinity, and extreme temperatures, limit plant growth and development, reducing crop yields. Therefore, a more comprehensive understanding of the signaling mechanisms and responses of plants to changing environmental conditions is crucial for improving sustainable agricultural productivity. Chemical screening was conducted to find novel small compounds that act as regulators of the abiotic stress signaling pathway using the ABA-inducible transgenic reporter line. Small molecules called stress response regulators (SRRs) were isolated by screening a synthetic library composed of 14,400 small compounds, affecting phenotypes such as seed germination, root growth, and gene expression in response to multiple abiotic stresses. Seeds pretreated with SRR compounds positively affected the germination rate and radicle emergence of Arabidopsis and tomato plants under abiotic stress conditions. The SRR-priming treatment enhanced the transcriptional responses of abiotic stress-responsive genes in response to subsequent salt stress. The isolation of the novel molecules SRR1 and SRR2 will provide a tool to elucidate the complex molecular networks underlying the plant stress-tolerant responses.

Seed quality as a proxy of climate-ready orphan legumes: the need for a multidisciplinary and multi-actor vision

In developing countries, orphan legumes stand at the forefront in the struggle against climate change. Their high nutrient value is crucial in malnutrition and chronic diseases prevention. However, as the 'orphan' definition suggests, their seed systems are still underestimated and seed production is scanty. Seed priming is an effective, sustainable strategy to boost seed quality in orphan legumes for which up-to-date guidelines are required to guarantee reliable and reproducible results. How far are we along this path? What do we expect from seed priming? This brings to other relevant questions. What is the socio-economic relevance of orphan legumes in the Mediterranean Basin? How to potentiate a broader cultivation in specific regions? The case study of the BENEFIT-Med (Boosting technologies of orphan legumes towards resilient farming systems) project, developed by multidisciplinary research networks, envisions a roadmap for producing new knowledge and innovative technologies to improve seed productivity through priming, with the long-term objective of promoting sustainability and food security for/in the climate-sensitive regions. This review highlights the existing drawbacks that must be overcome before orphan legumes could reach the state of 'climate-ready crops'. Only by the integration of knowledge in seed biology, technology and agronomy, the barrier existing between research bench and local agricultural fields may be overcome, generating high-impact technical innovations for orphan legumes. We intend to provide a powerful message to encourage future research in line with the United Nations Agenda 2030 for Sustainable Development.

Seed priming with potassium nitrate alleviates the high temperature stress by modulating growth and antioxidant potential in carrot seeds and seedlings

Early season carrot (Daucus carota) production is being practiced in Punjab, Pakistan to meet the market demand but high temperature hampers the seed germination and seedling establishment which cause marked yield reduction. Seed priming with potassium nitrate breaks the seed dormancy and improves the seed germination and seedling growth potential but effects vary among the species and ecological conditions. The mechanism of KNO3 priming in high temperature stress tolerance is poorly understood yet. Thus, present study aimed to evaluate high temperature stress tolerance potential of carrot seeds primed with potassium nitrate and impacts on growth, physiological, and antioxidant defense systems. Carrot seeds of a local cultivar (T-29) were primed with various concentration of KNO3 (T0: unprimed (negative control), T1: hydroprimed (positive control), T2: 50 mM, T3:100mM, T4: 150 mM, T5: 200 mM, T6: 250 mM and T7: 300 mM) for 12 h each in darkness at 20 ± 2℃. Seed priming with 50 mM of KNO3 significantly enhanced the seed germination (36%), seedling growth (28%) with maximum seedling vigor (55%) and also exhibited 16.75% more carrot root biomass under high temperature stress as compared to respective control. Moreover, enzymatic activities including peroxidase, catalase, superoxidase dismutase, total phenolic contents, total antioxidants contents and physiological responses of plants were also improved in response to seed priming under high temperature stress. By increasing the level of KNO3, seed germination, growth and root biomass were reduced. These findings suggest that seed priming with 50 mM of KNO3 can be an effective strategy to improve germination, growth and yield of carrot cultivar (T-29) under high temperature stress in early cropping. This study also proposes that KNO3 may induces the stress memory by heritable modulations in chromosomal structure and methylation and acetylation of histones that may upregulate the hormonal and antioxidant activities to enhance the stress tolerance in plants.

The Impact of ZnO and Fe2O3 Nanoparticles on Sunflower Seed Germination, Phenolic Content and Antiglycation Potential

The enhancement of seed germination by using nanoparticles (NPs) holds the potential to elicit the synthesis of more desired compounds with important biomedical applications, such as preventing protein glycation, which occurs in diabetes. Here, we used 7 nm and 100 nm ZnO and 4.5 nm and 16.7 nm Fe2O3 NPs to treat sunflower seeds. We evaluated the effects on germination, total phenolic content, and the anti-glycation potential of extracted polyphenols. Sunflower seeds were allowed to germinate in vitro after soaking in NP solutions of different concentrations. Polyphenols were extracted, dosed, and used in serum albumin glycation experiments. The germination speed of seeds was significantly increased by the 100 nm ZnO NPs and significantly decreased by the 4.5 nm Fe2O3 NPs. The total phenolic content (TPC) of seeds was influenced by the type of NP, as ZnO NPs enhanced TPC, and the size of the NPs, as smaller NPs led to improved parameters. The polyphenols extracted from seeds inhibited protein glycation, especially those extracted from seeds treated with 7 nm ZnO. The usage of NPs impacted the germination speed and total polyphenol content of sunflower seeds, highlighting the importance of NP type and size in the germination process.

Assessment of Various Nanoprimings for Boosting Pea Germination and Early Growth in Both Optimal and Drought-Stressed Environments

One of the main climate change-related variables limiting agricultural productivity that ultimately leads to food insecurity appears to be drought. With the use of a recently discovered nanopriming technology, seeds can endure various abiotic challenges. To improve seed quality and initial growth of 8-day-old field pea seedlings (cv. NS Junior) under optimal and artificial drought (PEG-induced) laboratory conditions, this study aimed to assess the efficacy of priming with three different nanomaterials: Nanoplant Ultra (Co, Mn, Cu, Fe, Zn, Mo, and Se), Nanoplant Ca-Si (Ca, Si, B, and Fe), and Nanoplant Sulfur (S). The findings indicate that nanopriming seed treatments have a positive impact on seed quality indicators, early plant growth, and drought resilience in field pea plants established in both optimal and drought-stressed conditions. Nevertheless, all treatments showed a positive effect, but their modes of action varied. Nanoplant Ultra proved to be the most effective under optimal conditions, whereas Nanoplant Ca-Si and Nanoplant Sulfur were the most efficient under drought stress. After a field evaluation, the examined comprehensive nanomaterials may be utilized as priming agents for pea seed priming to boost seed germination, initial plant growth, and crop productivity under various environmental conditions.

Chitosan-GSNO Nanoparticles and Silicon Priming Enhance the Germination and Seedling Growth of Soybean (Glycine max L.)

Soybean, a major legume crop, has seen a decline in its production owing to challenges in seed germination and the development of seedlings. Thus, in this study, we systematically investigated the influence of various chitosan-S-nitrosoglutathione (chitosan-GSNO) nanoparticle (0, 25, 50, and 100 µM) and Si (0, 0.5, and 1 mM) priming concentrations on soybean seed germination and seedling growth over five different priming durations (range: 1-5 h at each concentration). Significant differences were observed in all parameters, except seedling diameter, with both treatments. Seed germination was significantly enhanced after 3 h of priming in both treatments. The final germination percentage (FGP), peak germination percentage (PGP), vigor index (VI), seedling biomass (SB), hypocotyl length (HL), and radical length (RL) of 100 μM chitosan-GSNO-nanoparticle-primed seeds increased by 20.3%, 41.3%, 78.9%, 25.2%, 15.7%, and 65.9%, respectively, compared with those of the control; however, the mean germination time (MGT) decreased by 18.43%. Si priming at 0.5 mM increased the FGP, PGP, VI, SB, HL, and RL by 13.9%, 55.17%, 39.2%, 6.5%, 22.5%, and 25.1%, respectively, but reduced the MGT by 12.29% compared with the control treatment. Chitosan-GSNO and Si treatment up-regulated the relative expression of gibberellic acid (GA)-related genes (GmGA3ox3 and GmGA2ox1) and down-regulated that of abscisic acid (ABA)-related genes (GmABA2, GmAAO3, and GmNCED5). Chitosan-GSNO and Si application increased bioactive GA4 levels and simultaneously reduced ABA content. Hence, the use of exogenous chitosan-GSNO nanoparticles and Si as priming agents had a beneficial effect on seed germination and seedling growth because of the up-regulation in the expression of GA and down-regulation in the expression of ABA. Additional research is needed to understand the combined impact of Si and chitosan-GSNO nanoparticles, including their effects on the expression levels of other hormones and genes even in the later growth stage of the crop.

Creating Climate-Resilient Crops by Increasing Drought, Heat, and Salt Tolerance

Over the years, the changes in the agriculture industry have been inevitable, considering the need to feed the growing population. As the world population continues to grow, food security has become challenged. Resources such as arable land and freshwater have become scarce due to quick urbanization in developing countries and anthropologic activities; expanding agricultural production areas is not an option. Environmental and climatic factors such as drought, heat, and salt stresses pose serious threats to food production worldwide. Therefore, the need to utilize the remaining arable land and water effectively and efficiently and to maximize the yield to support the increasing food demand has become crucial. It is essential to develop climate-resilient crops that will outperform traditional crops under any abiotic stress conditions such as heat, drought, and salt, as well as these stresses in any combinations. This review provides a glimpse of how plant breeding in agriculture has evolved to overcome the harsh environmental conditions and what the future would be like.

Plant-Based Biostimulants for Seeds in the Context of Circular Economy and Sustainability

Plant-based biostimulants (PBs), agents rich in bioactive compounds, are emerging as key players able to sustainably improve plant growth and crop productivity to address food security. PBs are generally applied as foliar spray or soil irrigation, while more recently, the application as seed priming treatments is being envisaged as a highly sustainable method to also improve seed quality and germination. Therefore, this review proposes to explore the use of PBs for the seeds industry, specifically discussing about the relevance of product market values, sustainable methods for their production, why and how PBs are used for seed priming, and pinpointing specific strengths and challenges. The collected research studies indicate that PBs applied to seeds result in improved germination, seedling growth, and stress tolerance, although the molecular mechanisms at work are still largely overlooked. The high variability of bioactive molecules and used sources point towards a huge reservoir of nature-based solutions in support of sustainable agriculture practices.

Strigolactone GR24-mediated mitigation of phosphorus deficiency through mycorrhization in aerobic rice

Strigolactones (SLs) are a new class of plant hormones that play a significant role in regulating various aspects of plant growth promotion, stress tolerance and influence the rhizospheric microbiome. GR24 is a synthetic SL analog used in scientific research to understand the effects of SL on plants and to act as a plant growth promoter. This study aimed to conduct hormonal seed priming at different concentrations of GR24 (0.1, 0.5, 1.0, 5.0 and 10.0 µM with and without arbuscular mycorrhizal fungi (AMF) inoculation in selected aerobic rice varieties (CR Dhan 201, CR Dhan 204, CR Dhan 205, and CR Dhan 207), Kasalath-IC459373 (P-tolerant check), and IR-36 (P-susceptible check) under phosphorus (P)-deficient conditions to understand the enhancement of growth and priming effects in mycorrhization. Our findings showed that seed priming with 5.0 µM SL GR24 enhanced the performance of mycorrhization in CR Dhan 205 (88.91 %), followed by CR Dhan 204 and 207, and AMF sporulation in CR Dhan 201 (31.98 spores / 10 gm soil) and CR Dhan 207 (30.29 spores / 10 g soil), as well as rice growth. The study showed that the highly responsive variety CR Dhan 207 followed by CR Dhan 204, 205, 201, and Kasalath IC459373 showed higher P uptake than the control, and AMF treated with 5.0 µM SL GR24 varieties CR Dhan 205 followed by CR Dhan 207 and 204 showed the best performance in plant growth, chlorophyll content, and soil functional properties, such as acid and alkaline phosphatase activity, soil microbial biomass carbon (MBC), dehydrogenase activity (DHA), and fluorescein diacetate activity (FDA). Overall, AMF intervention with SL GR24 significantly increased plant growth, soil enzyme activity, and uptake of P compared to the control. Under P-deficient conditions, seed priming with 5.0 µM strigolactone GR24 and AMF inoculum significantly increased selected aerobic rice growth, P uptake, and soil enzyme activities. Application of SLs formulations with AMF inoculum in selected aerobic rice varieties, CR Dhan 207, CR Dhan 204, and CR Dhan 205, will play an important role in mycorrhization, growth, and enhancement of P utilization under P- nutrient deficient conditions.

Mitigation effect of alpha-tocopherol and thermo-priming in Brassica napus L. under induced mercuric chloride stress

Soil pollution with heavy metals has grown to be a big hassle, leading to the loss in farming production particularly in developing countries like Pakistan, where no proper channel is present for irrigation and extraction of these toxic heavy metals. The present study aims to ameliorate the damages caused by heavy metal ions (Hg-Mercury) on rapeseed (Brassica napus L.) via a growth regulator (α-tocopherol 150 mg/L) and thermopriming technique at 4 °C and 50 °C to maintain plant agronomical and physiological characteristics. In pot experiments, we designed total of 11 treatments viz.( T0 (control), T1 (Hg4ppm), T2 (Hg8ppm), T3 (Hg4ppm + 4 °C), T4 (Hg4ppm + 4 °C + tocopherol (150 m/L)), T5 (Hg4ppm + 50 °C), T6 (Hg4ppm + 50 °C + tocopherol (150 mg/L)), T7 (Hg8ppm + 4 °C), T8 (Hg8ppm + 4 °C + tocopherol (150 mg/L)), T9 (Hg8ppm + 50 °C), T10 (Hg8ppm + 50 °C + tocopherol (150 mg/L) the results revealed that chlorophyll content at p < 0.05 with growth regulator and antioxidant enzymes such as catalase, peroxidase, and malondialdehyde enhanced up to the maximum level at T5 = Hg4ppm + 50 °C (50 °C thermopriming under 4 ppm mercuric chloride stress), suggesting that high temperature initiate the antioxidant system to reduce photosystem damage. However, protein, proline, superoxide dismutase at p < 0.05, and carotenoid, soluble sugar, and ascorbate peroxidase were increased non-significantly (p > 0.05) 50 °C thermopriming under 8 ppm high mercuric chloride stress (T9 = Hg8ppm + 50 °C) representing the tolerance of selected specie by synthesizing osmolytes to resist oxidation mechanism. Furthermore, reduction in % MC (moisture content) is easily improved with foliar application of α-tocopherol and 50 °C thermopriming and 4 ppm heavy metal stress at T6 = Hg4ppm + 50 °C + α-tocopherol (150 mg/L), with a remarkable increase in plant vigor and germination energy. It has resulted that the inhibitory effect of only lower concentration (4 ppm) of heavy metal stress was ameliorated by exogenous application of α-tocopherol and thermopriming technique by synthesizing high levels of proline and antioxidant activities in maintaining seedling growth and development on heavy metal contaminated soil.

Genotype-specific germination behavior induced by sustainable priming techniques in response to water deprivation stress in rice

Water stress brought about by climate change is among the major global concerns threatening food security. Rice is an important staple food which requires high water resources. Being a semi-aquatic plant, rice is particularly susceptible to drought. The aim of this work was to develop techniques directed to promote rice resilience to water deprivation stress during germination by implementing specific seed priming treatments. Five popular Italian rice varieties were subjected to priming treatments using novel, sustainable solutions, like poly-gamma-glutamic acid (γ-PGA), denatured γ-PGA (dPGA), and iron (Fe) pulsing, alone or in combination. The effect of the developed priming methods was tested under optimal conditions as well as under water deprivation stress imposed by polyethylene glycol (PEG) treatments. The priming efficacy was phenotypically determined in terms of germination behavior by measuring a series of parameters (germinability, germination index, mean germination time, seed vigor index, root and shoot length, germination stress tolerance index). Biochemical analyses were carried out to measure the levels of iron uptake and accumulation of reactive oxygen species (ROS). Integrative data analyses revealed that the rice varieties exhibited a strong genotype- and treatment-specific germination behavior. PEG strongly inhibited germination while most of the priming treatments were able to rescue it in all varieties tested except for Unico, which can be defined as highly stress sensitive. Molecular events (DNA repair, antioxidant response, iron homeostasis) associated with the transition from seed to seedling were monitored in terms of changes in gene expression profiles in two varieties sensitive to water deprivation stress with different responses to priming. The investigated genes appeared to be differentially expressed in a genotype-, priming treatment-, stress- and stage-dependent manner. The proposed seed priming treatments can be envisioned as sustainable and versatile agricultural practices that could help in addressing the impact of climate challenges on the agri-food system.

Seed bio-priming enhanced salt stress tolerance of maize (Zea mays L.) seedlings by regulating the antioxidant system and miRNA expression

Maize (Zea mays) is moderately sensitive to salt stress. Therefore, increasing salinity in soil causes the arrestment of physiological processes and retention of growth and development, consequently leading to yield loss. Although many strategies have been launched to improve salt stress tolerance, plant growth-promoting rhizobacteria (PGPR) are considered the most promising approach due to being more environmentally friendly and agronomically sustainable than chemicals. Therefore, this study aims to investigate the potential of Bacillus spp. and the role of microRNA-mediated genetic regulation in maize subjected to seed bio-priming application to mitigate salt stress effects. To this end, maize seeds were bio-primed with the vegetative form of B. pumilus, B. licheniformis, and B. coagulans both individually or combined, subsequently treated to NaCl, and the seedlings were screened morphologically, physiologically, and transcriptionally. The study revealed that seed bio-priming with B. licheniformis reduced the stress effects of maize seedlings by increasing catalase (CAT) and ascorbate peroxidase (APX) activities by 2.5- and 3-fold, respectively, tolerating the decrease in chlorophyll content (CC), upregulating miR160d expression which led to a 36% increase in root fresh weight (RFW) and a 39% increase in shoot fresh weight (SFW). In conclusion, Bacillus spp. successfully alleviated salt stress effects on maize by modulating antioxidant enzymes and miRNA expression.

Pre- and post-melatonin mitigates the effect of ionizing radiation-induced damage in wheat by modulating the antioxidant machinery

As an indolamine, melatonin (C13H16N2O2) performs essential roles in the regulation of plant growth and development and ameliorates the harmful effects of abiotic stresses. This study examined two types of melatonin application, pre-sowing (prMel) and application during growth (ptMel), in wheat (Triticum aestivum L.) seedlings exposed to four different doses (100, 200, 300, and 400 Gy) of radioactive cobalt (60Co) gamma rays as dry seeds to investigate their ameliorative effects on ionizing radiation (IR) stress. Peroxidase, catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase, mono- and dihydroxyperoxidase, and phenylalanine ammonia-lyase activities, and levels of lipid peroxidation, H2O2, and total glutathione (GSH), and phenolic acids (PHAs) in soluble free, ester, glycoside and ester-bound forms were examined in the seedlings. Both melatonin applications were found to increase lipid peroxidation, H2O2, and GSH contents previously reduced by gamma irradiation. The IR treatment-induced increases in enzyme activities were significantly reduced by melatonin applications. The study findings indicated that high doses of IR resulted in significant decreases in the activity and levels of the measured traits. The predominant PHAs in the tissues were vanillic, ferulic, and p-coumaric acids. In addition, ptMel application combined with IR stress lowered the total phenolic acid contents in the soluble forms while increasing those in the cell wall-bound form. In conclusion, the antioxidant system in the seedlings exposed to the different gamma ray doses was regulated by prMel and ptMel applications in such a manner as to alleviate IR stress-induced oxidatives damages in the wheat.

Seed priming with nano-silica effectively ameliorates chromium toxicity in Brassica napus

Plant yield is severely hampered by chromium (Cr) toxicity, affirming the urgent need to develop strategies to suppress its phyto-accumulation. Silicon dioxide nanoparticles (SiO2 NPs) have emerged as a provider of sustainable crop production and resistance to abiotic stress. But, the mechanisms by which seed-primed SiO2 NPs palliate Cr-accumulation and its toxic impacts in Brassica napus L. tissues remains poorly understood. To address this gap, present study examined the protective efficacy of seed priming with SiO2 NPs (400 mg/L) in relieving the Cr (200 µM) phytotoxicity mainly in B. napus seedlings. Results delineated that SiO2 NPs significantly declined the accumulation of Cr (38.7/35.9%), MDA (25.9/29.1%), H2O2 (27.04/36.9%) and O2• (30.02/34.7%) contents in leaves/roots, enhanced the nutrients acquisition, leading to improved photosynthetic performance and better plant growth. SiO2 NPs boosted the plant immunity by upregulating the transcripts of antioxidant (SOD, CAT, APX, GR) or defense-related genes (PAL, CAD, PPO, PAO and MT-1), GSH (assists Cr-vacuolar sequestration), and modifying the subcellular distribution (enhances Cr-proportion in cell wall), thereby confer tolerance to ultrastructural damages under Cr stress. Our first evidence to establish the Cr-detoxification by seed-primed SiO2 NPs in B. napus, indicated the potential of SiO2 NPs as stress-reducing agent for crops grown in Cr-contaminated areas.

Seed priming mitigates high salinity impact on germination of bread wheat (Triticum aestivum L.) by improving carbohydrate and protein mobilization

Salinity is increasingly considered as a major environmental issue, which threatens agricultural production by decreasing yield traits of crops. Seed priming is a useful and cost-effective technique to alleviate the negative effects of salinity and to enable a fast and uniform germination. In this context, we quantified the effects of priming with gibberellic acid (GP), calcium chloride (CP), and mannitol (MP) on seed germination of three bread wheat cultivars and investigated their response when grown at high salinity conditions (200 mM NaCl). Salt exposure strongly repressed seed imbibition and germination potential and extended germination time, whereas priming enhanced uniformity and seed vigor. Seed preconditioning alleviated the germination disruption caused by salt stress to varying degrees. Priming mitigating effect was agent-dependent with regard to water status (CP and MP), ionic imbalance (CP), and seed reserve mobilization (GP). Na+ accumulation in seedling tissues significantly impaired carbohydrate and protein mobilization by inhibiting amylase and proteases activities but had lesser effects on primed seeds. CP attenuated ionic imbalance by limiting sodium accumulation. Gibberellic acid was the most effective priming treatment for promoting the germination of wheat seeds under salt stress. Moreover, genotypic differences in wheat response to salinity stress were observed between varieties used in this study. Ardito, the oldest variety, seems to tolerate better salinity in priming-free conditions; Aubusson resulted the most salt-sensitive cultivar but showed a high germination recovery under priming conditions; Bologna showed an intermediate behavior.

Chemical priming of plant defense responses to pathogen attacks

Plants can acquire an improved resistance against pathogen attacks by exogenous application of natural or artificial compounds. In a process called chemical priming, application of these compounds causes earlier, faster and/or stronger responses to pathogen attacks. The primed defense may persist over a stress-free time (lag phase) and may be expressed also in plant organs that have not been directly treated with the compound. This review summarizes the current knowledge on the signaling pathways involved in chemical priming of plant defense responses to pathogen attacks. Chemical priming in induced systemic resistance (ISR) and systemic acquired resistance (SAR) is highlighted. The roles of the transcriptional coactivator NONEXPRESSOR OF PR1 (NPR1), a key regulator of plant immunity, induced resistance (IR) and salicylic acid signaling during chemical priming are underlined. Finally, we consider the potential usage of chemical priming to enhance plant resistance to pathogens in agriculture.

Seed Nano-Priming with Calcium Oxide Maintains the Redox State by Boosting the Antioxidant Defense System in Water-Stressed Carom (Trachyspermum ammi L.) Plants to Confer Drought Tolerance

This paper explores the potential of nano seed priming with calcium oxide nanoparticles in maintaining the redox status in carom (Trachyspermum ammi L.) plants by modulating non-enzymatic antioxidants and enzymatic antioxidants. Calcium oxide nanoparticles were prepared in four testing regimes comprising 25, 50, 75, and 100 ppm along with the control treatment of 0 ppm (distilled water). Priming was performed by soaking the carom seeds in the aerated water, and plants were grown under split plots corresponding to drought and water. Seed priming with 75 ppm CaONPs reduced hydrogen peroxide, malondialdehyde contents and electrolyte leakage by 23.3%, 35.9% and 31.6%, respectively, in the water-stressed carom plants. The glutathione s-transferase, superoxide dismutase and peroxidase functions improved under water stress by 42.3%, 24.1% and 44.8%, respectively, in the carom plants raised through 100 ppm primed seeds with CaO_NPs. Priming induced better Ca²⁺ signaling, which affected the enzymes of the ascorbate glutathione cycle, enabling them to maintain redox status in the carom plants exposed to drought stress. The morpho-agronomic traits of carom plants in terms of number of umbels, hundred seeds weights, shoot and root length and biomass improved significantly upon seed priming treatments. Seed priming with CaO_NPs is a viable strategy to combat reactive oxygen species-mediated damages in the carom plants.

Molecular dynamics of seed priming at the crossroads between basic and applied research

The potential of seed priming is still not fully exploited. Our limited knowledge of the molecular dynamics of seed pre-germinative metabolism is the main hindrance to more effective new-generation techniques. Climate change and other recent global crises are disrupting food security. To cope with the current demand for increased food, feed, and biofuel production, while preserving sustainability, continuous technological innovation should be provided to the agri-food sector. Seed priming, a pre-sowing technique used to increase seed vigor, has become a valuable tool due to its potential to enhance germination and stress resilience under changing environments. Successful priming protocols result from the ability to properly act on the seed pre-germinative metabolism and stimulate events that are crucial for seed quality. However, the technique still requires constant optimization, and researchers are committed to addressing some key open questions to overcome such drawbacks. In this review, an update of the current scientific and technical knowledge related to seed priming is provided. The rehydration-dehydration cycle associated with priming treatments can be described in terms of metabolic pathways that are triggered, modulated, or turned off, depending on the seed physiological stage. Understanding the ways seed priming affects, either positively or negatively, such metabolic pathways and impacts gene expression and protein/metabolite accumulation/depletion represents an essential step toward the identification of novel seed quality hallmarks. The need to expand the basic knowledge on the molecular mechanisms ruling the seed response to priming is underlined along with the strong potential of applied research on primed seeds as a source of seed quality hallmarks. This route will hasten the implementation of seed priming techniques needed to support sustainable agriculture systems.

Noninvasive Methods to Detect Reactive Oxygen Species as a Proxy of Seed Quality

ROS homeostasis is crucial to maintain radical levels in a dynamic equilibrium within physiological ranges. Therefore, ROS quantification in seeds with different germination performance may represent a useful tool to predict the efficiency of common methods to enhance seed vigor, such as priming treatments, which are still largely empirical. In the present study, ROS levels were investigated in an experimental system composed of hydroprimed and heat-shocked seeds, thus comparing materials with improved or damaged germination potential. A preliminary phenotypic analysis of germination parameters and seedling growth allowed the selection of the best-per-forming priming protocols for species like soybean, tomato, and wheat, having relevant agroeconomic value. ROS levels were quantified by using two noninvasive assays, namely dichloro-dihydro-fluorescein diacetate (DCFH-DA) and ferrous oxidation-xylenol orange (FOX-1). qRT-PCR was used to assess the expression of genes encoding enzymes involved in ROS production (respiratory burst oxidase homolog family, RBOH) and scavenging (catalase, superoxide dismutase, and peroxidases). The correlation analyses between ROS levels and gene expression data suggest a possible use of these indicators as noninvasive approaches to evaluate seed quality. These findings are relevant given the centrality of seed quality for crop production and the potential of seed priming in sustainable agricultural practices.

Impact of climate perturbations on seeds and seed quality for global agriculture

In agriculture, seeds are the most basic and vital input on which croplands productivity depends. These implies a good starting material, good production lines and good storage options. High-quality seed lots must be free of pests and pathogens and contain a required degree of genetic purity. Seeds need also to be stored in good condition between harvest and later sowing, to insure later on the field a good plant density and higher crop yield. In general, these parameters are already widely accepted and considered in many countries where advanced technologies evaluate them. However, the more and more frequently devastating climate changes observed around the world has put seed quality under threat, and current seeds may not be adapted to hazardous and unpredictable conditions. Climate-related factors such as temperature and water availability directly affect seed development and later germination. For these reasons, investigating seed quality in response to climate changes is a step to propose new crop varieties and practices that will bring solutions for our future.

Localization of Lipid Droplets in Embryonic Axis Radicle Cells of Soybean Seeds under Various Imbibition Regimes Indicates Their Role in Desiccation Tolerance

Desiccation tolerance allows plant seeds to remain viable during desiccation and subsequent re-hydration. In this study, we tried to develop an experimental system to understand the difference between desiccation tolerant and desiccation sensitive radicle cells by examining excised embryonic axes after re-desiccation and subsequent imbibition under various regimes. Embryonic axes excised from soybean (Glycine max (L.) Merr.) seeds imbibed for 3 h to 15 h which remained attached to the cotyledons during imbibition would grow normally after 24 h of desiccation and re-imbibition on wet filter paper. By contrast, when the embryonic axes excised after 3 h imbibition of seeds were kept on wet filter paper for 12 h to 16 h, their growth was significantly retarded after 24 h of desiccation and subsequent re-imbibition. Numerous lipid droplets were observed lining the plasma membrane and tonoplasts in radicle cells of desiccation tolerant embryonic axes before and after desiccation treatment. By contrast, the lipid droplets lining the plasma membrane and tonoplasts became very sparse in radicle cells that were placed for longer times on wet filter paper before desiccation. We observed a clear correlation between the amount of lipid droplets lining plasma membranes and the ability to grow after desiccation and re-imbibition of the excised embryonic axes. In addition to the reduction of lipid droplets in the cells, a gradual increase in starch grains was observed. Large starch grains accumulated in the radicle cells of those axes that failed to grow further.

The comparative effects of manganese nanoparticles and their counterparts (bulk and ionic) in Artemisia annua plants via seed priming and foliar application

The world has experienced an unprecedented boom in nanotechnology. Nanoparticles (NPs) are likely to act as biostimulants in various plants due to having high surface/volume value. However, understanding the actual effect of NPs is essential to discriminate them from other counterparts in terms of being applicable, safe and cost-effective. This study aimed to assay the impact of manganese(III) oxide (Mn₂O₃)-NPs via seed-priming (SP) and a combination of SP and foliar application (SP+F) on Artemisia. annua performance at several times intervals and comparison with other available manganese (Mn) forms. Our findings indicate that SP with MnSO₄ and Mn₂O₃-NPs stimulates the processes that occur prior to germination and thus reduces the time for radicle emergence. In both applications (i.e., SP and +F), none of the Mn treatments did show adverse phytotoxic on A. annua growth at morpho-physio and biochemical levels except for Mn₂O_3, which delayed germination and further plant growth, subsequently. Besides, from physio-biochemical data, it can be inferred that the general mechanism mode of action of Mn is mainly attributed to induce the photosynthetic processes, stimulate the superoxide dismutase (SOD) activity, and up-regulation of proline and phenolic compounds. Therefore, our results showed that both enzymatic and non-enzymatic antioxidants could be influenced by the application of Mn treatments in a type-dependent manner. In general, this study revealed that Mn₂O₃-NPs at the tested condition could be used as biostimulants to improve germination, seedling development and further plant growth. However, they are not as effective as MnSO₄ treatments. Nonetheless, these findings can be used to consider and develop Mn₂O₃-NPs priming in future studies to improve seed germination and seedling quality in plants.

The bacterial world inside the plant

Sustainable agriculture requires the recruitment of bacterial agents to reduce the demand for mineral fertilizers and pesticides such as bacterial endophytes. Bacterial endophytes represent a potential alternative to the widespread use of synthetic fertilizers and pesticides in conventional agriculture practices. Endophytes are formed by complex microbial communities and microorganisms that colonize the plant interior for at least part of their life. Their functions range from mutualism to pathogenicity. Bacterial endophytes colonize plant tissues, and their composition and diversity depend on many factors, including the plant organ, physiological conditions, plant growth stage, and environmental conditions. The presence of endophytes influences several vital activities of the host plant. They can promote plant growth, elicit a defense response against pathogen attack, and lessen abiotic stress. Despite their potential, especially with regard to crop production and environmental sustainability, research remains sparse. This review provides an overview of the current research, including the concept of endophytes, endophytes in plant organs, endophyte colonization, nutrient efficiency use, endophytes and crop nutrition, inoculation with synergistic bacteria, the effect of inoculum concentration on plant root microbiota and synthetic communities. It also examines the practical opportunities and challenges when utilizing endophytes in the field of sustainable agriculture. Finally, it explores the importance of these associations with regard to the future of agriculture and the environment.

Combined Effect of Zinc Oxide Nanoparticles and Bacteria on Osmolytes and Antioxidative Parameters of Rice (Oryza sativa L.) Plant Grown in Heavy Metal-Contaminated Water

With the advancement in nanotechnology, the use of nanoparticles has been enhanced dramatically in biomedical, agriculture, and industrial processes. However, the combined effect of nanoparticles and bacteria on plant growth in heavy metal (Cd, Cr, Cu, and Pb)-contaminated wastewater is greatly limited. Therefore, the recent work was designed to determine the synergistic impact of green synthesized zinc oxide nanoparticles (ZnO-NPs) (5-10 mg/L) and Bacillus spp. (Bacillus cereus and Lysinibacillus macroides) on the physiological and biochemical activities of rice seedlings under heavy metal- (HM-) contaminated water. The results revealed that germination percentage (36%), root-shoot length (5.11 and 3.41 cm), fresh shoot-root weight (0.05 and 0.011 g), dry shoot-root weight (0.008 and 0.009 g), Chl a, Chl b, and carotenoid (5.4, 3.2 mg/g, and 4.3 μg/g), total soluble sugar (TSS) (26.44 mg/g), and total soluble protein (TSP) (21.99 mg/g) content considerably reduced in the plant tissues while combined impact of bacteria and ZnO NPs alleviates HM stress in contaminated water and improved seed germination (70%), root-shoot length (9.93 and 11.82 cm), fresh shoot-root weight (0.125 and 0.131 g), dry shoot-root weight (0.0532 and 0.042 g), Chl a, Chl b, and carotenoid (18.8, 13.9 mg/g, and 17.1 μg/g), TSS (57.651 mg/g), and TSP (47.990 mg/g) content. Lipid peroxidation induced by HM stress increased the amount of thiobarbituric acid reactive substances (TBRAS) (17.321 nM/mg) and hydrogen peroxide (H2O2) content (14.5 μM/g), stress markers such as glycine betaine (GB) (40.731 mg/g) and proline (Pro) (38.812 μmol/g) and antioxidant enzymes (SOD, POD, CAT, and APX) (180.87 U/mg, 450.677, 0.1066, and 0.631 μm/min/mg) under HM stress while the combined effect of ZnO NPs and bacteria reduced TBRAS (5.431 nM/mg), H2O2 content (2.25 μM/g), stress markers such as GB (24.731 mg/g) and Pro (18.811 μmol/g), and SOD, POD, CAT, and APX (187.53, 194.88, 0.061, and 0.271 μm/min/mg) contents. The present study suggested a potential role of combined impact of nanoparticles and bacteria in remediation of heavy metals from wastewater by improving plant growth.