Foliar Application of Nano-Silicon Improves the Physiological and Biochemical Characteristics of ‘Kalamata’ Olive Subjected to Deficit Irrigation in a Semi-Arid Climate

Nanosilicon application changes the morphological attributes and essential oil compositions of hemp (Cannabis sativa L.) under water deficit stress

Various practical strategies have been employed to mitigate the detrimental effects of water deficit stress on plants such as application of nano-stimulants. Nanosilicon plays a crucial role in alleviating the deleterious impacts of both abiotic and biotic stresses in plants by modulating various phyto-morphological and physiological processes. This study aimed to examine the combined effects of drought stress and nanosilicon application on the morphological traits and essential oil content and compositions of hemp (Cannabis sativa L.), in which four-week-old seedlings were subjected to irrigation treatments at four levels, including 100% (control), 80% (mild stress), 60% (moderate stress) and 40% (severe stress) field capacity and nanosilicon at three concentrations (0, 0.5 and 1.5 mM) in a completely randomized factorial design experiment with three replications for 40 days. The results showed that the maximum plant height (109.07 cm), number of nodes (33.3), and number of flowering branches (29.4) were recorded under the treatment of 1.5 mM nanosilicon and 100% FC. The lowest fresh and dry weights of aerial parts were associated to the severe drought stress (40% FC) without nanosilicon application. The mild water stress (80% FC) combined with foliar application of 1.5 mM nanosilicon led to highest EO content (0.17%) compared with the other treatments. However, the highest content of cannabidiol in the essential oil was achieved in the severe water stress (40% FC) and treatment of 0.5 mM nanosilicon. The results showed that the application of nanosilicon improved the morphological characteristics and also changed the content and compositions of the hemp plants under drought stress conditions.

Foliar Nutrition Strategies for Enhancing Phenolic and Amino Acid Content in Olive Leaves

Studies on selenium (Se) and silicon (Si) foliar biostimulation of different plants have been shown to affect concentrations of phenolic compounds. However, their effects on olive (Olea europaea L.) primary and secondary metabolites have not been fully investigated. Therefore, the effects of foliar sprayed Si and Se and their combination on the concentration of phenols, selected metabolites involved in the phenol biosynthesis, and mineral elements concentrations were determined in olive leaves of the field-grown cultivar Leccino. During the summer period, leaves were foliar sprayed three times, after which were sampled 30 days after the corresponding application. In general, foliar treatment of Si or Se increased the concentrations of several predominant phenolic compounds, such as oleuropein, oleacein, and specific flavonoids. The effects were especially pronounced after the third application in the harvest time sampling time. Amino acids and other phenol precursors were also significantly affected. The effects were phenol-specific and depended on the treatment, sampling time, and treatment × sampling time interaction. The response of verbascoside to the applied treatments appeared to be closely linked to corresponding changes in its amino acid precursors, such as tyrosine, while its connection with tryptophan and IAA has to be cautiously considered. In contrast, for other phenolic compounds like secoiridoids, a clear interdependence with their precursors was not identified, likely due to the more complex nature of their biosynthesis. The effects on the concentrations of elements other than Se and Si were milder.

Biodegradable microplastics induce profound changes in lettuce (Lactuca sativa) defense mechanisms and to some extent deteriorate growth traits

The development of agricultural technologies has intensified the use of plastic in this sector. Products of plastic degradation, such as microplastics (MPs), potentially threaten living organisms, biodiversity and agricultural ecosystem functioning. Thus, biodegradable plastic materials have been introduced to agriculture. However, the effects of biodegradable plastic substitutes on soil ecosystems are even less known than those of traditional ones. Here, we studied the effects of environmentally relevant concentrations of MPs prepared from a biodegradable plastic (a starch-polybutylene adipate terephthalate blend, PBAT-BD-MPs) on the growth and defense mechanisms of lettuce (Lactuca sativa) in CLIMECS system (CLImatic Manipulation of ECosystem Samples). PBAT-BD-MPs in the highest concentrations negatively affected some traits of growth, i.e., dry weight percentage, specific leaf area, and both C and N contents. We observed more profound changes in plant physiology and biochemistry, as PBAT-BD-MPs decreased chlorophyll content and triggered a concerted response of plant defense mechanisms against oxidative stress. In conclusion, exposure to PBAT-BD-MPs induced plant oxidative stress and activated plant defense mechanisms, leading to oxidative homeostasis that sustained plant growth and functioning. Our study highlights the need for in-depth understanding of the effect of bioplastics on plants.

Enhancing plant resilience: Nanotech solutions for sustainable agriculture

The global population growth is driving up the demand for agricultural products, while traditional farming methods like those from the Green Revolution are becoming unsustainable due to climate change. To address these challenges and ensure agricultural sustainability, innovative techniques, such as nanotechnology, are essential to meet rising food demands and enhance agricultural sustainability. Nanotechnology, which promotes a more sustainable and resilient agricultural system while enhancing food security, is a key catalyst for the Agri-tech revolution. This review offers a progressive analysis of nanotechnology's role in managing plant stress. It explores how precision agriculture, particularly via nanosensors, is enhancing our comprehension of plant stress conditions. The integration of nanotechnology with genetic engineering methods, notably CRISPR-Cas technology, is also examined. Furthermore, the review considers the potential toxicological effects of nanoparticles (NPs) on both the environment and plants. Our review has the potential to make a significant impact on human food security by enhancing food production and availability while promoting sustainable agricultural practices. By tackling these challenges, we can contribute to a more reliable and sustainable food supply for the global population.

Application of Silica Nanoparticles Improved the Growth, Yield, and Grain Quality of Two Salt-Tolerant Rice Varieties under Saline Irrigation

Salt stress significantly reduces rice yield and quality and is a global challenge, especially in arid and semi-arid regions with limited freshwater resources. The present study was therefore conducted to examine the potential of silica nanoparticles (SiO2 NPs) in mitigating the adverse effects of saline irrigation water in salt-tolerant rice. Two salt-tolerant rice varieties, i.e., Y liangyou 957 (YLY957) and Jingliangyou 534 (JLY534), were irrigated with 0.6% salt solution to simulate high-salt stress and two SiO2 NPs were applied, i.e., control (CK) and SiO2 NPs (15 kg hm-2). The results demonstrated that the application of SiO2 NPs increased, by 33.3% and 23.3%, the yield of YLY957 and JLY534, respectively, compared with CK, which was primarily attributed to an increase in the number of grains per panicle and the grain-filling rate. Furthermore, the application of SiO2 NPs resulted in a notable enhancement in the chlorophyll content, leaf area index, and dry matter accumulation, accompanied by a pronounced stimulation of root system growth and development. Additionally, the SiO2 NPs also improved the antioxidant enzyme activities, i.e., superoxide dismutase, peroxidase, and catalase activity and reduced the malondialdehyde content. The SiO2 NPs treatment effectively improved the processing quality, appearance quality, and taste quality of the rice. Furthermore, the SiO2 NPs resulted in improvements to the rapid viscosity analyzer (RVA) pasting profile, including an increase in peak viscosity and breakdown values and a reduction in setback viscosity. The application of SiO2 NPs also resulted in a reduction in crystallinity and pasting temperature owing to a reduction in the proportion of B2 + B3 amylopectin chains. Overall, the application of silica nanoparticles improved the quality of rice yield under high-salt stress.

Silicon derived benefits to combat biotic and abiotic stresses in fruit crops: Current research and future challenges

Fruit crops are frequently subjected to biotic and abiotic stresses that can significantly reduce the absorption and translocation of essential elements, ultimately leading to a decrease in crop yield. It is imperative to grow fruits and vegetables in areas prone to drought, salinity, and extreme high, and low temperatures to meet the world's minimum nutrient demand. The use of integrated approaches, including supplementation of beneficial elements like silicon (Si), can enhance plant resilience under various stresses. Silicon is the second most abundant element on the earth crust, following oxygen, which plays a significant role in development and promote plant growth. Extensive efforts have been made to explore the advantages of Si supplementation in fruit crops. The application of Si to plants reinforces the cell wall, providing additional support through enhancing a mechanical and biochemical processes, thereby improving the stress tolerance capacity of crops. In this review, the molecular and physiological mechanisms that explain the beneficial effects of Si supplementation in horticultural crop species have been discussed. The review describes the role of Si and its transporters in mitigation of abiotic stress conditions in horticultural plants.

Integrated physiological, transcriptomic, and metabolomic analyses of drought stress alleviation in Ehretia macrophylla Wall. seedlings by SiO2 NPs (silica nanoparticles)

With environmental problems such as climate global warming, drought has become one of the major stress factors, because it severely affects the plant growth and development. Silicon dioxide nanoparticles (SiO2 NPs) are crucial for mitigating abiotic stresses suffered by plants in unfavorable environmental conditions and further promoting plant growth, such as drought. This study aimed to investigate the effect of different concentrations of SiO2 NPs on the growth of the Ehretia macrophylla Wall. seedlings under severe drought stress (water content in soil, 30-35%). The treatment was started by starting spraying different concentrations of SiO2 NPs on seedlings of Ehretia macrophyla, which were consistently under normal and severe drought conditions (soil moisture content 30-35%), respectively, at the seedling stage, followed by physiological and biochemical measurements, transcriptomics and metabolomics analyses. SiO2 NPs (100 mg·L-1) treatment reduced malondialdehyde and hydrogen peroxide content and enhanced the activity of antioxidant enzymes under drought stress. Transcriptomic analysis showed that 1451 differentially expressed genes (DEGs) in the leaves of E. macrophylla seedlings were regulated by SiO2 NPs under drought stress, and these genes mainly participate in auxin signal transduction and mitogen-activated protein kinase signaling pathways. This study also found that the metabolism of fatty acids and α-linolenic acids may play a key role in the enhancement of drought tolerance in SiO2 NP-treated E. macrophylla seedlings. Metabolomics studies indicated that the accumulation level of secondary metabolites related to drought tolerance was higher after SiO2 NPs treatment. This study revealed insights into the physiological mechanisms induced by SiO2 NPs for enhancing the drought tolerance of plants.

Polystyrene nanoparticles induce concerted response of plant defense mechanisms in plant cells

Recent advances in knowledge suggest that micro- and nanoplastics pose a threat to plant health, however, the responses of plants to this stressor are not well-known. Here we examined the response of plant cell defence mechanisms to nanoparticles of commonly used plastic, polystyrene. We used plant cell cultures of widely cultivated plants, the monocots wheat and barley (Triticum aestivum L., Hordeum vulgare L.) and the dicots carrot and tomato (Daucus carota L., Solanum lycopersicum L.). We measured the activities of enzymes involved in the scavenging of reactive oxygen species and nonenzymatic antioxidants and we estimated potential damages in plant cell structures and functioning via lipid peroxidation and DNA methylation levels. Our results demonstrate that the mode of action of polystyrene nanoparticles on plant cells involves oxidative stress. However, the changes in plant defence mechanisms are dependent on plant species, exposure time and nanoplastic concentrations. In general, both monocots showed similar responses to nanoplastics, but the carrot followed more the response of monocots than a second dicot, a tomato. Higher H2O2, lipid peroxidation and lower enzyme activities scavenging H2O2 suggest that tomato cells may be more susceptible to polystyrene-induced stress. In conclusion, polystyrene nanoplastics induce oxidative stress and the response of the plant defense mechanisms involving several chain reactions leading to oxidoreductive homeostasis.

The potential of SiK® fertilization in the resilience of chestnut plants to drought - a biochemical study

Silicon is an essential mineral nutrient, that plays a crucial role in the metabolic, biochemical, and functional mechanisms of many crops under environmental stress. In the current study, we evaluated the effect of SiK^® fertilization on the biochemical defense response in plants exposed to water stress. Castanea sativa plants were fertilized with different concentrations of potassium silicate (0, 5, 7.5, and 10 mM of SiK^®) and exposed to a non-irrigation phase and an irrigation phase. The results indicate that silicon promoted the synthesis of soluble proteins and decreased the proline content and the oxidative stress (reduced electrolyte leakage, lipid peroxidation, and hydrogen peroxide accumulation) in tissues, due to an increase in ascorbate peroxidase, catalase, and peroxidase activity, which was accompanied by the rise in total phenol compounds and the number of thiols under drought conditions. This study suggests that exogenous Si applications have a protective role in chestnut plants under water deficit by increasing their resilience to this abiotic stress.

What Makes the Life of Stressed Plants a Little Easier? Defense Mechanisms against Adverse Conditions

Plants experience a wide array of external factors, some of which negatively affect their metabolism, growth, and development [...].

Nanosilicon: An approach for abiotic stress mitigation and sustainable agriculture

Abiotic stresses causing extensive yield loss in various crops globally. Over the past few decades, the application of silicon nanoparticles (nSi) has emerged as one of the abiotic stress mitigators. The initial responses of plants are shown by the biogenesis of reactive oxygen species (ROS) to sustain cellular/organellar integrity to ensure in vivo operation of metabolic functions by regulating physiological and biochemical pathways during stress conditions. Plants have evolved various antioxidative systems to balance/maintain the process of homeostasis via enzymatic and non-enzymatic activities to repair the losses. In the adverse environment, supplementation of Si mitigates the stress condition and improved the growth and development of plants. Its ameliorative effects were correlated with the enhanced antioxidant enzymes activities to maintain the equilibrium between the ROS generation and reduction. However, there are limited studies covered the role of nSi in the abiotic stress condition. This review addresses the accumulation and/or uptake of nSi in several crops and its mode of action linked with improved plants' growth and tolerance capabilities to confer sustainable agriculture.

Stimulating the Growth, Anabolism, Antioxidants, and Yield of Rice Plants Grown under Salt Stress by Combined Application of Bacterial Inoculants and Nano-Silicon

The growth and development of rice face many issues, including its exposure to high soil salinity. This issue can be alleviated using new approaches to overwhelm the factors that restrict rice productivity. The objective of our investigation was the usage of the rhizobacteria (Pseudomonas koreensis and Bacillus coagulans) as plant growth-promoting rhizobacteria (PGPRs) and nano-silicon, which could be a positive technology to cope with the problems raised by soil salinity in addition to improvement the morpho-physiological properties, and productivity of two rice varieties (i.e., Giza 177 as salt-sensitive and Giza 179 as salt-tolerant). The findings stated that the application of combined PGPRs and nano-Si resulted in the highest soil enzymes activity (dehydrogenase and urease), root length, leaf area index, photosynthesis pigments, K⁺ ions, relative water content (RWC), and stomatal conductance (gs) while resulted in the reduction of Na⁺, electrolyte leakage (EL), and proline content. All these improvements are due to increased antioxidant enzymes activity such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), which decreased hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) under soil salinity in rice plants compared to the other treatments. Combined application of PGPRs and nano-Si to Giza 177 significantly surpassed Giza 179, which was neither treated with PGPR nor nano-Si in the main yield components (number of grains/panicles, 1000 grain weight, and grain yield as well as nutrient uptake. In conclusion, both PGPRs and nano-Si had stimulating effects that mitigated the salinity-deleterious effects and encouraged plant growth, and, therefore, enhanced the grain yield.

Application of Silica Nanoparticles in Combination with Two Bacterial Strains Improves the Growth, Antioxidant Capacity and Production of Barley Irrigated with Saline Water in Salt-Affected Soil

Exploitation of low-quality water or irrigation of field crops with saline water in salt-affected soil is a critical worldwide challenge that rigorously influences agricultural productivity and sustainability, especially in arid and semiarid zones with limited freshwater resources. Therefore, we investigated a synergistic amendment strategy for salt-affected soil using a singular and combined application of plant growth-promoting rhizobacteria (PGPR at 950 g ha⁻¹; Azotobacter chroococcum SARS 10 and Pseudomonas koreensis MG209738) and silica nanoparticles (SiNPs) at 500 mg L⁻¹ to mitigate the detrimental impacts of irrigation with saline water on the growth, physiology, and productivity of barley (Hordum vulgare L.), along with soil attributes and nutrient uptake during 2019/2020 and 2020/2021. Our field trials showed that the combined application of PGPR and SiNPs significantly improved the soil physicochemical properties, mainly by reducing the soil exchangeable sodium percentage. Additionally, it considerably enhanced the microbiological counts (i.e., bacteria, azotobacter, and bacillus) and soil enzyme activity (i.e., urease and dehydrogenase) in both growing seasons compared with the control. The combined application of PGPR and SiNPs alleviated the detrimental impacts of saline water on barley plants grown in salt-affected soil compared to the single application of PGPR or SiNPs. The marked improvement was due to the combined application of PGPR and SiNPs, which enhanced the physiological properties (e.g., relative chlorophyll content (SPAD), relative water content (RWC), stomatal conductance, and K/Na ratio), enzyme activity (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX)), and yield and yield-related traits and nutrient uptake (N, P, and K) of barley plants. Moreover, the Na+ content, hydrogen peroxide (H₂O₂) content, lipid peroxidation (MDA), electrolyte leakage (EL), and proline content were reduced upon the application of PGPR + SiNPs. These results could be important information for cultivating barley and other cereal crops in salt-affected soil under irrigation with saline water.