Green Synthesized Metal Oxide Nanoparticles Mediate Growth Regulation and Physiology of Crop Plants under Drought Stress

A review of nanotechnology in enzyme cascade to address challenges in pre-treating biomass

Nanotechnology has become a revolutionary technique for improving the preliminary treatment of lignocellulosic biomass in the production of biofuels. Traditional methods of pre-treatment have encountered difficulties in effectively degrading the intricate lignocellulosic composition, thereby impeding the conversion of biomass into fermentable sugars. Nanotechnology has enabled the development of enzyme cascade processes that present a potential solution for addressing the limitations. The focus of this review article is to delve into the utilization of nanotechnology in the pretreatment of lignocellulosic biomass through enzyme cascade processes. The review commences with an analysis of the composition and structure of lignocellulosic biomass, followed by a discussion on the drawbacks associated with conventional pre-treatment techniques. The subsequent analysis explores the importance of efficient pre-treatment methods in the context of biofuel production. We thoroughly investigate the utilization of nanotechnology in the pre-treatment of enzyme cascades across three distinct sections. Nanomaterials for enzyme immobilization, enhanced enzyme stability and activity through nanotechnology, and nanocarriers for controlled enzyme delivery. Moreover, the techniques used to analyse nanomaterials and the interactions between enzymes and nanomaterials are introduced. This review emphasizes the significance of comprehending the mechanisms underlying the synergy between nanotechnology and enzymes establishing sustainable and environmentally friendly nanotechnology applications.

Proteomic insights to decipher nanoparticle uptake, translocation, and intercellular mechanisms in plants

Advent of proteomic techniques has made it possible to identify a broad spectrum of proteins in living systems. Studying the impact of nanoparticle (NP)-mediated plant protein responses is an emerging field. NPs are continuously being released into the environment and directly or indirectly affect plant's biochemistry. Exposure of plants to NPs, especially crops, poses a significant risk to the food chain, leading to changes in underlying metabolic processes. Once absorbed by plants, NPs interact with cellular proteins, thereby inducing changes in plant protein patterns. Based on the reactivity, properties, and translocation of nanoparticles, NPs can interfere with proteins involved in various cellular processes in plants such as energy regulation, redox metabolism, and cytotoxicity. Such interactions of NPs at the subcellular level enhance ROS scavenging activity, especially under stress conditions. Although higher concentrations of NPs induce ROS production and hinder oxidative mechanisms under stress conditions, NPs also mediate metabolic changes from fermentation to normal cellular processes. Although there has been lots of work conducted to understand the different effects of NPs on plants, the knowledge of proteomic responses of plants toward NPs is still very limited. This review has focused on the multi-omic analysis of NP interaction mechanisms with crop plants mainly centering on the proteomic perspective in response to both stress and non-stressed conditions. Furthermore, NP-specific interaction mechanisms with the biological pathways are discussed in detail.

Physical, chemical, and biological routes of synthetic titanium dioxide nanoparticles and their crucial role in temperature stress tolerance in plants

Nanotechnology is attracting significant attention worldwide due to its applicability across various sectors. Titanium dioxide nanoparticles (TiO2NPs) are among the key nanoparticles (NPs) that have gained extensive practical use and can be synthesized through a wide range of physical, chemical, and green approaches. However, TiO2NPs have attracted a significant deal of interest due to the increasing demand for enhancing the endurance to abiotic stresses such as temperature stress. In this article, we discuss the effects of temperature stresses such as low (4 °C) and high temperatures (35 °C) on TiO2NPs. Due to climate change, low and high temperature stress impair plant growth and development. However, there are still many aspects of how plants respond to low and high temperature stress and how they influence plant growth under TiO2NPs treatments which are poorly understood. TiO2NPs can be utilized efficiently for plant growth and development, particularly under temperature stress, however the response varies according to type, size, shape, dose, exposure time, metal species, and other variables. It has been demonstrated that TiO2NPs are effective at enhancing the photosynthetic and antioxidant systems of plants under temperature stress. This analysis also identifies key knowledge gaps and possible future perspectives for the reliable application of TiO2NPs to plants under abiotic stress.

Nanoparticle-mediated amelioration of drought stress in plants: a systematic review

Drought stress remains one of the most detrimental environmental constraints that hampers plant growth and development resulting in reduced yield and leading to economic losses. Studies have highlighted the beneficial role of carbon-based nanomaterials (NMs) such as multiwalled carbon nanotubes (MWNTs), single-walled carbon nanotubes (SWNTs), graphene, fullerene, and metal-based nanoparticles (NPs) (Ag, Au, Cu, Fe2O3, TiO2, and ZnO) in plants under unfavorable conditions such as drought. NPs help plants cope with drought by improving plant growth indices and enhancing biomass. It improves water and nutrient uptake and utilization. It helps retain water by altering the cell walls and regulating stomatal closure. The photosynthetic parameters in NP-treated plants reportedly improved with the increase in pigment content and rate of photosynthesis. Due to NP exposure, the activation of enzymatic and nonenzymatic antioxidants has reportedly improved. These antioxidants play a significant role in the defense system against stress. Studies have reported the accumulation of osmolytes and secondary metabolites. Osmolytes scavenge reactive oxygen species, which can cause oxidative stress in plants. Secondary metabolites are involved in the water retention process, thus improving plant coping strategies with stress. The deleterious effects of drought stress are alleviated by reducing malondialdehyde resulting from lipid peroxidation. Reactive oxygen species accumulation is also controlled with NP treatment. Furthermore, NPs have been reported to regulate the expression of drought-responsive genes and the biosynthesis of phytohormones such as abscisic acid, auxin, gibberellin, and cytokinin, which help plants defend against drought stress. This study reviewed 72 journal articles from 192 Google Scholar, ScienceDirect, and PubMed papers. In this review, we have discussed the impact of NP treatment on morphological, physio-biochemical, and molecular responses in monocot and dicot plants under drought conditions with an emphasis on NP uptake, transportation, and localization.

Protective role of iron oxide nanocomposites on disease index, and biochemical resistance indicators against Fusarium oxysporum induced-cucumber wilt disease: In vitro, and in vivo studies

Recently nanocomposites have become a super-growth inducers as well as vital antifungal agents, which enhance plant growth and suppress plant diseases. A new strategy regarding the fabrication of humic acid (H) and boron (B) conjugated Fe₂O₃ nanocomposites was performed. Fe₂O₃ NP-B and Fe₂O₃ NP-H were synthesized in the presence of gamma-rays (as a direct reducing agent). Gamma-rays provoked reduction of metal ions due to the liberated reducing electrons, (e^-_aq), in aqueous solutions which can be considered as direct reduction. Antifungal potential against Fusarium oxysporum, the causative agent of wilt disease in cucumber was determined. Disease index percent, metabolic resistance indicators in cucumber plant as response to promotion of systemic resistance (SR) were recorded. Results illustrated that both Fe₂O₃ NPs-B and Fe₂O₃ NPs-H had antifungal activity against F. oxysporum in vitro as well as in vivo. Results revealed that minimum inhibitory concentrations of Fe₂O₃ NPs-B and Fe₂O₃ NPs-H were 0.25 and 0.125 mM, respectively. Application of Fe₂O₃ NPs-B (0.25 mM) and Fe₂O₃ NPs-H (0.125 mM) appeared highly reduced the cucumber wilt disease symptoms incidence caused by F. oxysporum, and recorded disease severity by 83.33%. Fe₂O₃ NPs-B was the best treatment reducing disease indexes by 20.83% and gave highly protection against wilt disease by 75.0% and came next Fe₂O₃ NPs-H which reduced disease indexes by 25% and gave 69.99% protection against disease. Fe₂O₃ NPs-B and Fe₂O₃ NPs-H treatments improved morphological traits, photosynthetic pigments, osmolytes, total phenol and antioxidant enzymes activities in both infected and non-infected plants. The beneficial effects of the Fe₂O₃ NPs-B and Fe₂O₃ NPs-H were extended to increase not only the total phenol, and total soluble protein content but also the activities of peroxidase (POD), and polyphenol oxidase (PPO) enzymes of the healthy and infected cucumber plants in comparison with control.

Agronomic Investigation of Spray Dispersion of Metal-Based Nanoparticles on Sunflowers in Real-World Environments

In environmental and agronomic settings, even minor imbalances can trigger a range of unpredicted responses. Despite the widespread use of metal-based nanoparticles (NPs) and new bio-nanofertilizers, their impact on crop production is absent in the literature. Therefore, our research is focused on the agronomic effect of spray application of gold nanoparticles anchored to SiO₂ mesoporous silica (AuSi-NPs), zinc oxide nanoparticles (ZnO-NPs), and iron oxide nanoparticles (Fe₃O₄-NPs) on sunflowers under real-world environments. Our findings revealed that the biosynthetically prepared AuSi-NPs and ZnO-NPs were highly effective in enhancing sunflower seasonal physiology, e.g., the value of the NDVI index increased from 0.012 to 0.025 after AuSi-NPs application. The distribution of leaf trichomes improved and the grain yield increased from 2.47 t ha^-1 to 3.29 t ha^-1 after ZnO-NPs application. AuSi-NPs treatment resulted in a higher content of essential linoleic acid (54.37%) when compared to the NPs-free control (51.57%), which had a higher determined oleic acid. No NPs or residual translocated metals were detected in the fully ripe sunflower seeds, except for slightly higher silica content after the AuSi-NPs treatment. Additionally, AuSi-NPs and NPs-free control showed wide insect biodiversity while ZnO-NPs treatment had the lowest value of phosphorus as anti-nutrient. Contradictory but insignificant effect on physiology, yield, and insect biodiversity was observed in Fe₃O₄-NPs treatment. Therefore, further studies are needed to fully understand the long-term environmental and agricultural sustainability of NPs applications.

Exogenous application of carbon nanoparticles alleviates drought stress by regulating water status, chlorophyll fluorescence, osmoprotectants, and antioxidant enzyme activity in Capsicum annumn L

Drought is one of the most important abiotic stresses that has a huge negative effect on crop yield. Carbon nanoparticles (CNPs) have received greater attention for their impact on the plants under abiotic stress conditions. However, it is urgently required to apply CNPs to the chili pepper (Capsicum annuum L. cv. Kaskada), which has not yet been studied. The goal of this study was to find out how CNPs affect the growth of chili pepper plants, chlorophyll pigments, proline content, and the activity of antioxidant enzymes when the plants are stressed by drought. Therefore, we synthesized and functionalized CNPs of oil fly ash by one-pot ball milling fabrication. X-ray photoelectron spectroscopy (XPS) was used to identify oxidative moieties on the CNPs surface after exposure to nitric and acetic acids. In the present study, functionalized CNPs were sprayed onto the leaves of 20-day-old plants at various concentrations (6 and 12 mg L^-1) to determine their effects. We demonstrate that drought stress considerably reduces the plant height, fresh weight (FW), and dry weight (DW). Nevertheless, the exogenous application of functionalized CNPs caused an increase in relative water content (RWC), chlorophyll stability index (CSI), and chlorophyll fluorescence (Fv/Fm) under drought stress. Exogenous functionalized CNPs dramatically increased proline content under drought by reducing abscisic acid (ABA) content in the leaves. When subjected to drought stress, functionalized CNPs boosted antioxidant activities such as superoxide dismutase (SOD) and catalase (CAT) activity. Overall, the positive effects of CNPs on chili pepper seedlings open up new possibilities for developing innovative agricultural techniques, especially when plants are grown in drought conditions.

Changes in Metal-Chelating Metabolites Induced by Drought and a Root Microbiome in Wheat

The essential metals Cu, Zn, and Fe are involved in many activities required for normal and stress responses in plants and their microbiomes. This paper focuses on how drought and microbial root colonization influence shoot and rhizosphere metabolites with metal-chelation properties. Wheat seedlings, with and without a pseudomonad microbiome, were grown with normal watering or under water-deficit conditions. At harvest, metal-chelating metabolites (amino acids, low molecular weight organic acids (LMWOAs), phenolic acids, and the wheat siderophore) were assessed in shoots and rhizosphere solutions. Shoots accumulated amino acids with drought, but metabolites changed little due to microbial colonization, whereas the active microbiome generally reduced the metabolites in the rhizosphere solutions, a possible factor in the biocontrol of pathogen growth. Geochemical modeling with the rhizosphere metabolites predicted Fe formed Fe-Ca-gluconates, Zn was mainly present as ions, and Cu was chelated with the siderophore 2'-deoxymugineic acid, LMWOAs, and amino acids. Thus, changes in shoot and rhizosphere metabolites caused by drought and microbial root colonization have potential impacts on plant vigor and metal bioavailability.

A Review of Sustainable Use of Biogenic Nanoscale Agro-Materials to Enhance Stress Tolerance and Nutritional Value of Plants

Climate change is more likely to have a detrimental effect on the world's productive assets. Several undesirable conditions and practices, including extreme temperature, drought, and uncontrolled use of agrochemicals, result in stresses that strain agriculture. In addition, nutritional inadequacies in food crops are wreaking havoc on human health, especially in rural regions of less developed countries. This could be because plants are unable to absorb the nutrients in conventional fertilizers, or these fertilizers have an inappropriate or unbalanced nutrient composition. Chemical fertilizers have been used for centuries and have considerably increased crop yields. However, they also disrupt soil quality and structure, eventually impacting the entire ecosystem. To address the situation, it is necessary to develop advanced materials that can release nutrients to targeted points in the plant-soil environment or appropriate receptors on the leaf in the case of foliar applications. Recently, nanotechnology-based interventions have been strongly encouraged to meet the world's growing food demand and to promote food security in an environmentally friendly manner. Biological approaches for the synthesis of nanoscale agro-materials have become a promising area of research, with a wide range of product types such as nanopesticides, nanoinsecticides, nanoherbicides, nanobactericides/fungicides, bio-conjugated nanocomplexes, and nanoemulsions emerging therefrom. These materials are more sustainable and target-oriented than conventional agrochemicals. In this paper, we reviewed the literature on major abiotic and biotic stresses that are detrimental to plant growth and productivity. We comprehensively discussed the different forms of nanoscale agro-materials and provided an overview of biological approaches in nano-enabled strategies that can efficiently alleviate plant biotic and abiotic stresses while potentially enhancing the nutritional values of plants.

Zinc oxide nanoparticles as potential hallmarks for enhancing drought stress tolerance in wheat seedlings

Drought is one of the major abiotic stresses which negatively affects plant growth and development. The current study evaluated the effects of drought on the growth, physiology, and biochemical attributes of wheat seedlings; and examined the role of foliar application of ZnO nanoparticles in alleviating drought-induced effects. Two wheat cultivars i.e., Anaj-2017 and FSD-2018 were grown in soil-filled pots and were subjected to 100% field capacity (FC) (well watered) and 50% of FC (drought stress). Whilst different treatments of ZnO nanoparticles spray included no spray, water spray, and 50, 100, and 150 ppm ZnO. Results demonstrated that drought caused a significant reduction in seedling fresh and dry weights, photosynthetic pigmentation, and antioxidant activities compared with a well-watered treatment. Nevertheless, the application of 100 and 150 ppm of ZnO nanoparticles effectively ameliorated the negative effects of drought and enhanced the performance of both cultivars under drought. Data revealed a significant increase in fresh and dry weight of shoot and root with the application of ZnO nanoparticles. A substantial increase of 73.68% and 28.51% in chlorophyll "a" and 26.15% and 50.02% in chlorophyll "b" was recorded with the application of 100 ppm of ZnO nanoparticles in Anaj-2017 and FSD-2018, respectively over control (0 ppm). The application of these nanoparticles also triggered the antioxidant defense system and protected the crop from oxidative damage. Averaged across different stress treatments, application of 150 and 100 ppm of ZnO nanoparticles increased the peroxidase activity by 60% and 72% in FSD-2018, and 15% and 23% in Anaj-2017, respectively compared with no spray. FSD-2018 outperformed Anaj-2017 regarding its overall performance under ZnO treatments and drought conditions. In a nutshell, it can be concluded that ZnO nanoparticles ameliorated the negative impacts of drought by improving the growth, physiology, and antioxidant defense of both wheat cultivars.

Green synthesis of spermine coated iron nanoparticles and its effect on biochemical properties of Rosmarinus officinalis

In this study, aqueous spinach extract was used for the green synthesis of iron nanoparticles. The surface of iron oxide nanoparticles was coated with spermine. The physicochemical properties of nanoparticles were investigated using UV-Vis, TGA, FTIR, VSM, TEM, and DLS. The results showed that the nanoparticles had a spherical structure. The surface charge of the Fe₃O₄-NPs increased from -3.2 to 18.42 (mV) after Fe₃O₄ coating by spermine. In order to investigate the effect of nanoparticles on physicochemical properties of rosemary under drought stress conditions, an experiment was carried out in a completely randomized design. The results showed that the amount of antioxidant enzymes and secondary metabolites increased significantly under drought stress. Moreover, the use of spermine-coated iron nanoparticles can be useful in increasing resistance to drought stress in plants by increasing the activity of some antioxidant enzymes and secondary metabolites. The biocompatibility of Nanoparticles in cell suspension was investigated. the ability of Fe₃O₄-SM NPs to interact with DNA and protect it against DNaseI and ultrasonic waves using agarose gel electrophoresis was studied. The ability of Fe₃O₄-SM to neutralize the negative charge of DNA and protect it against DNaseΙ and ultrasonic waves was confirmed using an agarose gel electrophoresis assay.

Characterizing stomatal attributes and photosynthetic induction in relation to biochemical changes in Coriandrum sativum L. by foliar-applied zinc oxide nanoparticles under drought conditions

Abiotic stress, particularly drought, will remain an alarming challenge for sustainable agriculture. New approaches have been opted, such as nanoparticles (NPs), to reduce the negative impact of drought stress and lessen the use of synthetic fertilizers and pesticides that are an inevitable problem these days. The application of zinc oxide nanoparticles (ZnO NPs) has been recognized as an effective strategy to enhance plant growth and crop production during abiotic stress. The aim of the current study was to investigate the role of ZnO NPs in drought stress management of drought-susceptible Coriandrum sativum L. (C. sativum) in two consecutive seasons. Drought regimes (moderate drought regime-MDR and intensive drought regime-IDR) were developed based on replenishment method with respect to 50% field capacity of fully irrigated (control) plants. The results showed that foliar application of 100 ppm ZnO NPs improved the net photosynthesis (Pn), stomatal conductance (C), and transpiration rate (E) and boosted up the photosynthetic capacity associated with photosynthetic active radiation in MDR. Similarly, 48% to 30% improvement of chlorophyll b content was observed in MDR and onefold to 41% in IDR during both seasons in ZnO NP-supplemented plants. The amount of abscisic acid in leaves showed a decreasing trend in MDR and IDR in the first season (40% and 30%) and the second season (49% and 33%) compared with untreated ZnO NP plants. The ZnO NP-treated plants showed an increment in total soluble sugars, total phenolic content, and total flavonoid content in both drought regimes, whereas the abaxial surface showed high stomatal density and stomatal index than the adaxial surface in foliar-supplied NP plants. Furthermore, ZnO NPs improve the magnitude of stomata ultrastructures like stomatal length, stomatal width, and pore length for better adaptation against drought. Principal component analysis revealed the efficacy of ZnO NPs in inducing drought tolerance in moderate and intensive stress regimes. These results suggest that 100 ppm ZnO NPs can be used to ameliorate drought tolerance in C. sativum plants.

The Role of Nanoparticles in Response of Plants to Abiotic Stress at Physiological, Biochemical, and Molecular Levels

In recent years, the global agricultural system has been unfavorably impacted by adverse environmental changes. These changes in the climate, in turn, have altered the abiotic conditions of plants, affecting plant growth, physiology and production. Abiotic stress in plants is one of the main obstacles to global agricultural production and food security. Therefore, there is a need for the development of novel approaches to overcome these problems and achieve sustainability. Nanotechnology has emerged as one such novel approach to improve crop production, through the utilization of nanoscale products, such as nanofertilizer, nanofungicides, nanoherbicides and nanopesticides. Their ability to cross cellular barriers makes nanoparticles suitable for their application in agriculture. Since they are easily soluble, smaller, and effective for uptake by plants, nanoparticles are widely used as a modern agricultural tool. The implementation of nanoparticles has been found to be effective in improving the qualitative and quantitative aspects of crop production under various biotic and abiotic stress conditions. This review discusses various abiotic stresses to which plants are susceptible and highlights the importance of the application of nanoparticles in combating abiotic stress, in addition to the major physiological, biochemical and molecular-induced changes that can help plants tolerate stress conditions. It also addresses the potential environmental and health impacts as a result of the extensive use of nanoparticles.

The role of nanoparticles in plant biochemical, physiological, and molecular responses under drought stress: A review

Drought stress (DS) is a serious challenge for sustaining global crop production and food security. Nanoparticles (NPs) have emerged as an excellent tool to enhance crop production under current rapid climate change and increasing drought intensity. DS negatively affects plant growth, physiological and metabolic processes, and disturbs cellular membranes, nutrient and water uptake, photosynthetic apparatus, and antioxidant activities. The application of NPs protects the membranes, maintains water relationship, and enhances nutrient and water uptake, leading to an appreciable increase in plant growth under DS. NPs protect the photosynthetic apparatus and improve photosynthetic efficiency, accumulation of osmolytes, hormones, and phenolics, antioxidant activities, and gene expression, thus providing better resistance to plants against DS. In this review, we discuss the role of different metal-based NPs to mitigate DS in plants. We also highlighted various research gaps that should be filled in future research studies. This detailed review will be an excellent source of information for future researchers to adopt nanotechnology as an eco-friendly technique to improve drought tolerance.

Preparation and application of nanostructured carbon from oil fly ash for growth promotion and improvement of agricultural crops with different doses

Application of carbon nanomaterials (CNMs) in agricultural production has piqued the interest of researchers. However, despite the enormous importance of CNMs in plant development, little is known about the effects of carbon nanoparticle (CNP) doses on plant physiological responses. Therefore, the aim of the current study was to check the effects of nanostructured carbon derived from oil fly ash (COFA), which was derived for the first time from high-energy ball-milling followed by a sonication process, on Phaseolus vulgaris L. and Cicer arietinum L. plants. We evaluated the plant physiological and biochemical parameters of the COFA-treated seedlings. Two different doses (4 mg L^-1 and 8 mg L^-1) of COFA and a control were studied. The results indicated that the germination rate (%), shoot length, root length, pod length, leaf area, fresh weight and dry weight were increased with the addition of COFA. Likewise, COFA increased the contents of chlorophyll pigments (Chla, Chlb, carotenoids), proteins, and carbohydrates in both species compared to the control. Finally, these findings showed that a COFA treatment at 4 mg L^-1 after ball milled-sonication in water (BMW4) constituted the best dose for growth and physiology. Our findings reveal that the novel strategy of COFA engineering led to a boost in the growth of Phaseolus vulgaris and Cicer arietinum. Our results have high potential for agricultural research and provide an impact on food security.

Calcium nanoparticles (Ca-NPs) improve drought stress tolerance in Brassica napus by modulating the photosystem II, nutrient acquisition and antioxidant performance

Foliar-application of nano-particles enhanced the foliar nutrient status and crop growth and yield. It is hypothesized that being second messenger molecule, supplementation of Ca²⁺ via calcium nanoparticles (Ca-NPs) can trigger various signaling pathways of physiological processes which can lead to alleviate the adverse effects of drought stress on the growth of canola (Brassica napus L.). Nano-enabled foliar-application could be an ideal strategy for advancing agricultural productivity. The present study explored the role of calcium nanoparticles (Ca-NPs) in alleviating drought stress in hydroponic Brassica napus (B. napus) plants. The foliar applied Ca-NPs were spherically shaped with an average size of 86 nm. Foliar application of 100 mg L^-1 Ca-NPs enhanced biomass of canola plants and considered as optimal dose. Ca-NPs at 100 mg L^-1 has a greater favorable impact on mesophyll ultrastructure, PSI and PSII efficacy, gas exchange parameters, chlorophyll content, and mineral absorption. The Ca-NPs treatment increased NPQ and Y(NPQ) under drought condition, indicating a higher PSII protective response to stressed conditions with better heat dissipation as a photoprotective component of NPQ. Ca-NPs application also reduced oxidative stress damage as measured by a reduction in reactive oxygen species (ROS) generation in terms of hydrogen peroxide and malondialdehyde (H₂O₂ and MDA). Furthermore, Ca-NPs induced drought tolerance response corresponded to an increased in key antioxidative defense enzymes (SOD, POD, CAT, APX), as well as non-enzymatic components (protease, lipoxygenase, proline, total soluble protein contents, endogenous hormonal biosynthesis), and secondary metabolite expression in B. napus plants. Taken together, the results of this study offer new insights into the physiological and molecular mechanisms by which B. napus responds to Ca-NPs exposure.

Exogenous Nitric Oxide and Silicon Applications Alleviate Water Stress in Apricots

Many plants confront several environmental stresses including heat, water stress, drought, salinity and high-metal concentrations that are crucial in defining plant productivity at different stages of their life cycle. Nitric oxide (NO) and Silicon (Si) are very effective molecules related in most of them and in varied biochemical events that have proven to be protective during cellular injury caused by some stress conditions like water stress. In the current work, we studied the effect of Si and NO alone and NO + Si interactive application on the response of plants exposed to water deficiency and well-watered plants for the Milord apricot variety. Water stress caused a reduce in chlorophyll content, dry and fresh weight, leaf area, stomatal conductivity, leaf relative water content and nutrient elements, while it caused an increase in leaf temperature, leaf proline, leaf malondialdehyde (MDA) content and membrane permeability. Si, NO and Si + NO combination treatments under water stress conditions significantly decreased the adverse effects of water stress on leaf temperature, leaf area, dry and fresh weight, stomata conductivity, relative water content, membrane permeability, L-proline and MDA content. The shoot dry weight, chlorophyll content, stomata conductivity and leaf relative water content in Si + NO treated apricot saplings increased by 59%, 55%, 12% and 8%, respectively. Combined treatment (Si + NO) was detected to be more effective than single applications (Si or NO) on some physiological, biochemical, morphological and nutritional properties of apricot under water stress conditions.

Effects of Phytogenically Synthesized Bimetallic Ag/ZnO Nanomaterials and Nitrogen-Based Fertilizers on Biochemical and Yield Attributes of Two Wheat Varieties

Wheat is the most important staple food worldwide, but wheat cultivation faces challenges from high food demand. Fertilizers are already in use to cope with the demand; however, more unconventional techniques may be required to enhance the efficiency of wheat cultivation. Nanotechnology offers one potential technique for improving plant growth and production by providing stimulating agents to the crop. In this study, plant-derived Ag/ZnO nanomaterials were characterized using UV-Vis spectroscopy, SEM, EDX, FTIR, and XRD methods. Various concentrations of phytogenically synthesized Ag/ZnO nanomaterials (20, 40, 60, and 80 ppm) and nitrogen-based fertilizers (urea and ammonium sulphate 50 and 100 mg/L) were applied to wheat varieties (Galaxy-13 and Pak-13). The results obtained from this research showed that application of 60 ppm Ag/ZnO nanomaterials with nitrogenous fertilizers (50 and 100 mg/L) were more effective in improving biochemistry and increasing yield of wheat plants by reducing enzymatic and non-enzymatic antioxidants (proline content, soluble sugar content, malondialdehyde, total phenolic content, total flavonoid content, superoxide dismutase, peroxidase, and catalase); and significantly increasing the protein content, number of grains per pot, spike length, 100-grain weight, grain yield per pot, and harvest index of both wheat varieties, compared to untreated plants. These findings allow us to propose Ag/ZnO nanomaterial formulation as a promising growth- and productivity-improvement strategy for wheat cultivation.

Moringa leaf extract and green algae improve the growth and physiological attributes of Mentha species under salt stress

Climate change, food scarcity, salt stress, and a rapidly growing population are just a few of the major global challenges. The current study examined into whether Moringa oleifera (L.) leaf extract and green algae (Ulva intestinalis) could help improve salt tolerance in Mentha species (Mentha piperita; Mentha longifolia). Moringa leaf extract (MLE) and green algae (GA) were applied to Mentha seedlings under three different salt treatments: 0 mM, 20 mM, 40 mM, 60 mM, and 90 mM, respectively. For each treatment, three biological replicates were conducted, with each replicate containing at least three plants. Mentha species were negatively affected by salt stress in terms of shoot length, fresh and dry weight, photosynthetic pigments, and antioxidant enzyme activities. However, the use of MLE and GA significantly improved the development and physiology of Mentha species under salt stress conditions. The MLE and GA treatments dramatically (p ≤ 0.001) increased SOD activity by 7% and 10%, CAT activity by 16% and 30%, APX activity by 34% and 56%, GPX activity by 12% and 47%, respectively, in Mentha piperita seedlings, which in turn strikingly increased superoxide dismutase (SOD) activity by 6% and 9%, catalase (CAT) activity by 15%, 28% and 44%, 27%, ascorbate peroxidase (APX) activity by 39% and 60%, glutathione peroxidase (GPX) activity by 23% and 58%, respectively, in Mentha longifolia seedlings, relative to the control. Aiming to answer questions about the relationship between plant extraction and traditional agricultural methods, this research greatly advances the goal of sustainable development for improving plant productivity by providing a much safer and more environmentally friendly adaptability.

Titanium and Zinc Based Nanomaterials in Agriculture: A Promising Approach to Deal with (A)biotic Stresses?

Abiotic stresses, such as those induced by climatic factors or contaminants, and biotic stresses prompted by phytopathogens and pests inflict tremendous losses in agriculture and are major threats to worldwide food security. In addition, climate changes will exacerbate these factors as well as their negative impact on crops. Drought, salinity, heavy metals, pesticides, and drugs are major environmental problems that need deep attention, and effective and sustainable strategies to mitigate their effects on the environment need to be developed. Besides, sustainable solutions for agrocontrol must be developed as alternatives to conventional agrochemicals. In this sense, nanotechnology offers promising solutions to mitigate environmental stress effects on plants, increasing plant tolerance to the stressor, for the remediation of environmental contaminants, and to protect plants against pathogens. In this review, nano-sized TiO₂ (nTiO₂) and ZnO (nZnO) are scrutinized, and their potential to ameliorate drought, salinity, and xenobiotics effects in plants are emphasized, in addition to their antimicrobial potential for plant disease management. Understanding the level of stress alleviation in plants by these nanomaterials (NM) and relating them with the application conditions/methods is imperative to define the most sustainable and effective approaches to be adopted. Although broad-spectrum reviews exist, this article provides focused information on nTiO₂ and nZnO for improving our understanding of the ameliorative potential that these NM show, addressing the gaps in the literature.

Nanoparticles as potential hallmarks of drought stress tolerance in plants

Plants are inevitably exposed to drought stress limiting their growth and causing yield loss, thus inciting food crises across the world. Nanoparticles (NPs) are regarded as effective and promising tools for modulation of crop yield to overcome current and future constraints in sustainable agricultural production by upgrading the plant tolerance mechanism under abiotic stress conditions, including drought. NPs exhibit alleviating effects against drought stress via induction of physiological and biochemical readjustments accompanied by modulation of gene expression involved in drought response/tolerance. NPs ameliorate drought-induced reduction in carbon assimilation via increasing the photosynthetic activity. The improved root growth, upregulation of aquaporins, modification of intracellular water metabolism, accumulation of compatible solutes and ion homeostasis are the major mechanisms used by NPs to mitigate the osmotic stress caused by water deficit. NPs reduce water loss from leaves through stomatal closure due to fostered abscisic acid (ABA) accumulation and ameliorate oxidative stress damage by reducing reactive oxygen species and activating the antioxidant defense system. This review provides an evolutionary foundation regarding drought stress in plant life and summarizes the interactions between NPs and plants under drought. The subsequent impact of NPs on plant development and productivity and recent nanobiotechnological approaches to improve drought stress resilience are presented. On the whole, this review highlights the significance of NPs in dealing with the global problem of water scarcity faced by farmers.

Nanomaterials as an alternative to increase plant resistance to abiotic stresses

The efficient use of natural resources without negative repercussions to the environment has encouraged the incursion of nanotechnology to provide viable alternatives in diverse areas, including crop management. Agriculture faces challenges due to the combination of different abiotic stresses where nanotechnology can contribute with promising applications. In this context, several studies report that the application of nanoparticles and nanomaterials positively affects crop productivity through different strategies such as green synthesis of nanoparticles, plant targeted protection through the application of nanoherbicides and nanofungicides, precise and constant supply of nutrients through nanofertilizers, and tolerance to abiotic stress (e.g., low or high temperatures, drought, salinity, low or high light intensities, UV-B, metals in soil) by several mechanisms such as activation of the antioxidant enzyme system that alleviates oxidative stress. Thus, the present review focuses on the benefits of NPs against these type of stress and their possible action mechanisms derived from the interaction between nanoparticles and plants, and their potential application for improving agricultural practices.

Spermine-Mediated Tolerance to Selenium Toxicity in Wheat (Triticum aestivum L.) Depends on Endogenous Nitric Oxide Synthesis

Excess selenium (Se) causes toxicity, and nitric oxide (NO)’s function in spermine (Spm)-induced tolerance to Se stress is unknown. Using wheat plants exposed to 1 mM sodium selenate—alone or in combination with either 1 mM Spm, 0.1 mM NO donor sodium nitroprusside (SNP) or 0.1 mM NO scavenger cPTIO—the potential beneficial effects of these compounds to palliate Se-induced stress were evaluated at physiological, biochemical and molecular levels. Se-treated plants accumulated Se in their roots (92%) and leaves (95%) more than control plants. Furthermore, Se diminished plant growth, photosynthetic traits and the relative water content and increased the levels of malondialdehyde, H₂O₂, osmolyte and endogenous NO. Exogenous Spm significantly decreased the levels of malondialdehyde by 28%, H₂O₂ by 37% and electrolyte leakage by 42%. Combined Spm/NO treatment reduced the Se content and triggered plant growth, photosynthetic traits, antioxidant enzymes and glyoxalase systems. Spm/NO also upregulated MTP1, MTPC3 and HSP70 and downregulated TaPCS1 and NRAMP1 (metal stress-related genes involved in selenium uptake, translocation and detoxification). However, the positive effects of Spm on Se-stressed plants were eliminated by the NO scavenger. Accordingly, data support the notion that Spm palliates selenium-induced oxidative stress since the induced NO elicits antioxidant defence upregulation but downregulates Se uptake and translocation. These findings pave the way for potential biotechnological approaches to supporting sustainable wheat crop production in selenium-contaminated areas.