ZnO nanoparticles efficiently enhance drought tolerance in Dracocephalum kotschyi through altering physiological, biochemical and elemental contents

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.

Response of Maize (Zea mays L.) to Foliar-Applied Nanoparticles of Zinc Oxide and Manganese Oxide Under Drought Stress

Maize (Zea mays L.) is an important crop grown for food, feed, and energy. In general, maize yield is decreased due to drought stress during the reproductive stages, and, hence, it is critical to improve the grain yield under drought. A field experiment was conducted with a split-plot design. The main factor was the irrigation regime viz. well-irrigated conditions and withholding irrigation from tasseling to grain filling for 21 days. The subplots include six treatments, namely, (i) the control (water spray), (ii) zinc oxide @ 100 ppm, (iii) manganese oxide @ 20 ppm, (iv) nZnO @ 100 ppm + nMnO @ 20 ppm, (v) Tamil Nadu Agricultural University (TNAU) Nano Revive @ 1.0%, and (vi) zinc sulfate 0.25% + manganese sulfate 0.25%. During drought stress, the anthesis-silking interval (ASI), chlorophyll a and b content, proline, starch, and carbohydrate fractions were recorded. At harvest, the grain-filling rate and duration, per cent green leaf area, and yield traits were recorded. Drought stress increased the proline (38.1%) and anthesis-silking interval (0.45 d) over the irrigated condition. However, the foliar application of ZnO (100 ppm) and nMnO (20 ppm) lowered the ASI and increased the green leaf area, leaf chlorophyll index, and proline content over water spray. The seed-filling rate (17%), seed-filling duration (11%), and seed yield (19%) decreased under drought. Nevertheless, the seed-filling rate (90%), seed-filling duration (13%), and seed yield (52%) were increased by the foliar spraying of nZnO (100 ppm) and nMnO (20 ppm) over water spray. These findings suggest that nZnO and nMnO significantly improve the grain yield of maize under drought stress conditions.

Synergistic Effects of Zinc Oxide Nanoparticles and Moringa Leaf Extracts on Drought Tolerance and Productivity of Cucurbita pepo L. Under Saline Conditions

This study investigated the combined effects of zinc oxide nanoparticles (Nano-Zn) and moringa leaf extract (MLE) on squash plants grown under water stress conditions in saline soil during 2021-2022. The research compared full irrigation (100% ETc) with water deficit conditions (60% ETc). While water deficit negatively impacted plant growth, yield, and various physiological parameters, the sequential application of Nano-Zn (at 50 or 100 mg L-1) with MLE (3%) significantly mitigated these adverse effects. The combined treatment proved more effective than individual applications, enhancing growth parameters, photosynthetic efficiency, and antioxidant systems. The treatment particularly improved stress tolerance by increasing protective compounds like soluble sugars and amino acids while reducing harmful H2O2 levels. The study concluded that sequential application of 100 mg L-1 Nano-Zn with MLE was optimal for enhancing squash performance under drought stress, with 50 mg L-1 Nano-Zn plus MLE as the second-best option.

Synergistic effects of Vachellia nilotica-derived zinc oxide nanoparticles and melatonin on drought tolerance in Fragaria × ananassa

This study investigates the synergistic effects of zinc oxide nanoparticles (ZnO NPs) and melatonin (MT) on Fragaria × ananassa (strawberry) plants under drought stress, focusing on growth, fruit biomass, and stress tolerance. ZnO NPs enhance nutrient uptake and stress resistance, while MT regulates growth hormones and boosts photosynthetic efficiency. Seven treatments were evaluated: T1 (no stress, 0.5 g/L ZnO NPs + 0.1 g/L MT), T2 (no stress, 0.5 g/L ZnO NPs), T3 (no stress, 0.1 g/L MT), T4 (drought stress, no application), T5 (drought stress, 0.5 g/L ZnO NPs + 0.1 g/L MT), T6 (drought stress, 0.5 g/L ZnO NPs), and T7 (drought stress, 0.1 g/L MT). Growth and stress parameters included shoot/root length, fruit biomass, bud number, chlorophyll content, oxidative stress markers (H₂O₂, MDA), and antioxidant enzyme activities in the leaves of Fragaria × ananassa. The combined treatment (ZnO NPs + MT) consistently outperformed others, achieving the highest growth metrics under both conditions: shoot length (22.33 ± 1.53 cm non-stress, 15.00 ± 1.53 cm drought), root length (18.67 ± 1.53 cm non-stress, 12.00 ± 1.53 cm drought), and fruit biomass (9.55 ± 0.31 g non-stress, 5.02 ± 0.23 g drought). Bud formation peaked at 3.33 ± 0.58 buds/plant non-stress and 2.00 ± 0.00 buds/plant drought. Under drought, the combined treatment also enhanced chlorophyll content (2.47 ± 0.20 mg/g FW) and significantly reduced H₂O₂ (28.67 ± 2.52 µmol/g FW) and MDA (4.21 ± 0.10 µmol/g FW) levels, while maximizing antioxidant enzyme activities (SOD: 121.67 ± 7.64 U/g FW, POD: 206.33 ± 14.84 U/g FW, CAT: 48.00 ± 3.61 U/g FW). These findings highlight the combined application of ZnO NPs and MT as a promising strategy to enhance growth and stress tolerance in strawberry plants, warranting further research on optimized concentrations, delivery methods, and molecular mechanisms.

Multifaceted impacts of nanoparticles on plant nutrient absorption and soil microbial communities

With the growth of the global population and the increasing scarcity of resources, the sustainability and efficiency improvement of agricultural production have become urgent needs. The rapid development of nanotechnology provides new solutions to this challenge, especially the application of nanoparticles in agriculture, which is gradually demonstrating its unique advantages and broad prospects. Nonetheless, various nanoparticles can influence plant growth in diverse manners, often through distinct mechanisms of action. Beyond their direct effects on the plant itself, they frequently alter the physicochemical properties of the soil and modulate the structure of microbial communities in the rhizosphere. This review focuses intently on the diverse methods through which nanoparticles can modulate plant growth, delving deeply into the interactions between nanoparticles and plants, as well as nanoparticles with soil and microbial communities. The aim is to offer a comprehensive reference for the utilization of functionalized nanoparticles in the agricultural sector.

Foliar-applied silicon and zinc nanoparticles improve plant growth, biochemical attributes, and essential oil profile of fennel (Foeniculum vulgare) under different irrigation regimes

The comparative efficacy of silicon (Si) and zinc (Zn) nanoparticles (NPs) in mitigating drought stress in fennel (Foeniculum vulgare ) remains largely unexplored. This study evaluated the impact of Si NPs and Zn NPs on enhancing plant growth and physiological-biochemical attributes of fennel under varying irrigation regimes. The 2-year study was a split-pot design with irrigation at three irrigation levels (100, 75, and 50% field capacity, FC) and five treatments of foliar application of Si and Zn NPs (control, 1mM Si NP, 2mM Si NP, 1mM Zn NP, 2mM Zn NP). Results showed that drought stress reduced plant performance. Increases in superoxide dismutase (SOD, 131%) and catalase (CAT, 276%) were seen after a 50% FC drought without the use of Si and Zn NPs. Conversely, biological yield (34%), seed yield (44%), chlorophyll a +b (26%), relative water content (RWC, 21%), and essential oil (EO) yield (50%) were all reduced. However, application of Zn and Si, particularly 1mM Si and 2mM Zn, greatly mitigated drought stress via lowering CAT and SOD activity and enhancing plant yield, chlorophyll content, RWC, and EO. The composition of the EO consisted primarily of anethole, followed by limonene, fenchone, and estragole. During drought conditions, monoterpene hydrocarbons increased while oxygenated monoterpenes decreased. The opposite trend was observed for Si and Zn NPs. Our results suggest that applying Zn NPs at 2mM followed by Si NPs at 1mM improved plant resilience and EO yield in fennel plants under water stress.

Silicon nanoparticles improved the osmolyte production, antioxidant defense system, and phytohormone regulation in Elymus sibiricus (L.) under drought and salt stress

Drought and salt stress negatively influence the growth and development of various plant species. Thus, it is crucial to overcome these stresses for sustainable agricultural production and the global food chain. Therefore, the present study investigated the potential effects of exogenous silicon nanoparticles (SiNPs) on the physiological and biochemical parameters, and endogenous phytohormone contents of Elymus sibiricus under drought and salt stress. Drought stress was given as 45% water holding capacity, and salt stress was given as 120 mM NaCl. The seed priming was done with different SiNP concentrations: SiNP1 (50 mg L-1), SiNP2 (100 mg L-1), SiNP3 (150 mg L-1), SiNP4 (200 mg L-1), and SiNP5 (250 mg L-1). Both stresses imposed harmful impacts on the analyzed parameters of plants. However, SiNP5 increased the chlorophylls and osmolyte accumulation such as total proteins by 96% and 110% under drought and salt stress, respectively. The SiNP5 significantly decreased the oxidative damage and improved the activities of SOD, CAT, POD, and APX by 10%, 54%, 104%, and 211% under drought and 42%, 75%, 72%, and 215% under salt stress, respectively. The SiNPs at all concentrations considerably improved the level of different phytohormones to respond to drought and salt stress and increased the tolerance of Elymus plants. Moreover, SiNPs decreased the Na+ and increased K+ concentrations in Elymus suggesting the reduction in salt ion accumulation under salinity stress. Overall, exogenous application (seed priming/dipping) of SiNPs considerably enhanced the physio-biochemical and metabolic responses, resulting in an increased tolerance to drought and salt stresses. Therefore, this study could be used as a reference to further explore the impacts of SiNPs at molecular and genetic level to mitigate abiotic stresses in forages and related plant species.

Metabolome and transcriptome reprogramming underlying tomato drought resistance triggered by a Pseudomonas strain

Although amelioration of drought stress by Plant Growth Promoting Rhizobacteria (PGPR) is a well-documented phenomenon, the combined molecular and metabolic mechanisms governing this process remain unclear. In these lines, the present study aimed to provide new insights in the underlying drought attenuating mechanisms of tomato plants inoculated with a PGP Pseudomonas putida strain, by using a combination of metabolomic and transcriptomic approaches. Following Differentially Expressed Gene analysis, it became evident that inoculation resulted in a less disturbed plant transcriptome upon drought stress. Untargeted metabolomics highlighted the differential metabolite accumulation upon inoculation, as well as the less metabolic reprograming and the lower accumulation of stress-related metabolites for inoculated stressed plants. These findings were in line with morpho-physiological evidence of drought stress mitigation in the inoculated plants. The redox state modulation, the more efficient nitrogen assimilation, as well as the differential changes in amino acid metabolism, and the induction of the phenylpropanoid biosynthesis pathway, were the main drought-attenuating mechanisms in the SAESo11-inoculated plants. Shifts in pathways related to hormonal signaling were also evident upon inoculation at a transcript level and in conjunction with carbon metabolism regulation, possibly contributed to a drought-attenuation preconditioning. The identified signatory molecules of SAESo11-mediated priming against drought included aspartate, myo-inositol, glutamate, along with key genes related to trehalose, tryptophan and cysteine synthesis. Taken together, SAESo11-inoculation provides systemic effects encompassing both metabolic and regulatory functions, supporting both seedling growth and drought stress amelioration.

Application of Silicon, Zinc, and Zeolite Nanoparticles-A Tool to Enhance Drought Stress Tolerance in Coriander Plants for Better Growth Performance and Productivity

Drought stress in arid regions is a serious factor affecting yield quantity and quality of economic crops. Under drought conditions, the application of nano-elements and nano-agents of water retention improved the water use efficiency, growth performance, and yield quantity of drought-stressed plants. For this objective, two field experiments were performed and organized as randomized complete block designs with six replications. The treatments included kaolin (5 t. ha-1) bentonite (12.5 t. ha-1), perlite (1.25 t.ha-1), N-zeolite (1.3 L.ha-1), N-silicon (2.5 L.ha-1), and N-zinc (2.5 L.ha-1). The current study showed that the application of silicon, zinc, and zeolite nanoparticles only positively influenced the morphological, physiological, and biochemical properties of the drought-stressed coriander plant. Exogenous application of N-silicon, N-zinc, and N-zeolite recorded the higher growth parameters of drought-stressed plants; namely, plant fresh weight, plant dry weight, leaf area, and root length than all the other treatments in both seasons. The improvement ratio, on average for both seasons, reached 17.93, 17.93, and 18.85% for plant fresh weight, 73.46, 73.46, and 75.81% for plant dry weight, 3.65, 3.65, and 3.87% for leaf area, and 17.46, 17.46, and 17.16% for root length of drought-stressed plants treated with N-silicon, N-zinc, and N-zeolite, respectively. For physiological responses, the application of N-zeolite, N-silicon, and N-zinc significantly increased leaf chlorophyll content, photosynthetic rate, water use efficiency, chlorophyll fluorescence, and photosystem II efficiency compared with the control in both seasons, respectively. Similar results were observed in antioxidant compounds, nutrient accumulation, and phytohormones. In contrast, those treatments markedly reduced the value of transpiration rate, nonphotochemical quenching, MDA, ABA, and CAT compared to control plants. Regarding the seed and oil yield, higher seed and oil yields were recorded in drought-stressed plants treated with N-zeolite followed by N-silicon and N-zinc than all the other treatments. Application of N-zeolite, N-silicon and N-zinc could be a promising approach to improve plant growth and productivity as well as to alleviate the adverse impacts of drought stress on coriander plants in arid and semi-arid areas.