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

Metallic allies in drought resilience: Unveiling the influence of silver and zinc oxide nanoparticles on enhancing tomato (Solanum lycopersicum) resistance through oxidative stress regulation

The escalating influence of environmental changes has heightened the physiological challenges faced by plants, with drought stress increasingly recognized as a critical global issue significantly impeding affecting the crop productivity. This study investigates the effectiveness of metal nano particles such as zinc oxide nanoparticles (ZnO NPs) and silver nanoparticles (Ag NPs) in mitigating drought stress in Solanum lycopersicum. The foliar application of ZnO NPs (500 ppm) and/or Ag NPs (500 ppm), individually or in combination, significantly alleviated drought stress-induced. This mitigation was evidenced by enhanced antioxidant enzymes activity viz., catalase (64%), peroxidase (76%), superoxide dismutase (78%), chlorophyll content (31%) & photosynthesis (37%), and protein levels (15%). Furthermore, ZnO NPs and Ag NPs effectively mitigated oxidative stress and lipid peroxidation, as evidence by reduced accumulation of malondialdehyde (11%). Remarkably, the combined application of ZnO NPs and Ag NPs expedited the water-splitting capacity and facilitated electron exchange through redox reactions under drought stress. Consequently, these enhancements positively influenced the morpho-physiological characteristics such as height (28%), fresh weight (31%), dry weight (29%) and net photosynthetic rate (37%) of S. lycopersicum. These findings underscore the promising potential of metal NPs, such as ZnO NPs and Ag NPs, in mitigating drought stress, offering valuable insights for sustainable crop production amidst evolving environmental challenges.

Nanoparticles as a Tool for Alleviating Plant Stress: Mechanisms, Implications, and Challenges

Plants, being sessile, are continuously exposed to varietal environmental stressors, which consequently induce various bio-physiological changes in plants that hinder their growth and development. Oxidative stress is one of the undesirable consequences in plants triggered due to imbalance in their antioxidant defense system. Biochemical studies suggest that nanoparticles are known to affect the antioxidant system, photosynthesis, and DNA expression in plants. In addition, they are known to boost the capacity of antioxidant systems, thereby contributing to the tolerance of plants to oxidative stress. This review study attempts to present the overview of the role of nanoparticles in plant growth and development, especially emphasizing their role as antioxidants. Furthermore, the review delves into the intricate connections between nanoparticles and plant signaling pathways, highlighting their influence on gene expression and stress-responsive mechanisms. Finally, the implications of nanoparticle-assisted antioxidant strategies in sustainable agriculture, considering their potential to enhance crop yield, stress tolerance, and overall plant resilience, are discussed.

Research progress of the detection and analysis methods of heavy metals in plants

Heavy metal (HM)-induced stress can lead to the enrichment of HMs in plants thereby threatening people's lives and health via the food chain. For this reason, there is an urgent need for some reliable and practical techniques to detect and analyze the absorption, distribution, accumulation, chemical form, and transport of HMs in plants for reducing or regulating HM content. Not only does it help to explore the mechanism of plant HM response, but it also holds significant importance for cultivating plants with low levels of HMs. Even though this field has garnered significant attention recently, only minority researchers have systematically summarized the different methods of analysis. This paper outlines the detection and analysis techniques applied in recent years for determining HM concentration in plants, such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), X-ray absorption spectroscopy (XAS), X-ray fluorescence spectrometry (XRF), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), non-invasive micro-test technology (NMT) and omics and molecular biology approaches. They can detect the chemical forms, spatial distribution, uptake and transport of HMs in plants. For this paper, the principles behind these techniques are clarified, their advantages and disadvantages are highlighted, their applications are explored, and guidance for selecting the appropriate methods to study HMs in plants is provided for later research. It is also expected to promote the innovation and development of HM-detection technologies and offer ideas for future research concerning HM accumulation in plants.

Efficacy of zinc-based nanoparticles in alleviating the abiotic stress in plants: current knowledge and future perspectives

Due to sessile, plants are unable to avoid unfavorable environmental conditions which leads to inducing serious negative effects on plant growth, crop yield, and food safety. Instead, various approaches were employed to mitigate the phytotoxicity of these emerging contaminants from the soil-plant system. However, recent studies based on the exogenous application of ZnO NPs approve of their important positive potential for alleviating abiotic stress-induced phytotoxicity leads to ensuring global food security. In this review, we have comprehensively discussed the promising role of ZnO NPs as alone or in synergistic interactions with other plant growth regulators (PGRs) in the mitigation of various abiotic stresses, i.e., heavy metals (HMs), drought, salinity, cold and high temperatures from different crops. ZnO NPs have stress-alleviating effects by regulating various functionalities by improving plant growth and development. ZnO NPs are reported to improve plant growth by stimulating diverse alterations at morphological, physiological, biochemical, and ultrastructural levels under abiotic stress factors. We have explained the recent advances and pointed out research gaps in studies conducted in earlier years with future recommendations. Thus, in this review, we have also addressed the opportunities and challenges together with aims to uplift future studies toward effective applications of ZnO NPs in stress management.

Water stress memory in wheat/maize intercropping regulated photosynthetic and antioxidative responses under rainfed conditions

Drought is a most prevalent environmental stress affecting the productivity of rainfed wheat and maize in the semiarid Loess Plateau of China. Sustainable agricultural practices such as intercropping are important for enhancing crop performance in terms of better physiological and biochemical characteristics under drought conditions. Enzymatic and non-enzymatic antioxidant enzyme activities are associated with improved abiotic tolerance in crop plants, however, its molecular mechanism remains obscure. A 2-year field study was conducted to evaluate the influence of intercropping treatment viz. wheat mono-crop (WMC), maize mono-crop (MMC), intercropping maize (IM) and wheat (IW) crops, and nitrogen (N) application rates viz. control and full-dose of N (basal application at 150 and 235 kg ha-1 for wheat and maize, respectively) on chlorophyll fluorescence, gas exchange traits, lipid peroxidation, antioxidative properties and expression patterns of six tolerance genes in both crops under rainfed conditions. As compared with their respective monocropping treatments, IW and IM increased the Fo/Fm by 18.35 and 14.33%, PS-11 efficiency by 7.90 and 13.44%, photosynthesis by 14.31 and 23.97%, C-capacity by 32.05 and 12.92%, and stomatal conductance by 41.40 and 89.95% under without- and with-N application, respectively. The reductions in instantaneous- and intrinsic-water use efficiency and MDA content in the range of 8.76-26.30% were recorded for IW and IM treatments compared with WMC and MMC, respectively. Compared with the WMC and MMC, IW and IM also triggered better antioxidant activities under both N rates. Moreover, we also noted that intercropping and N addition regulated the transcript levels of six genes encoding non-enzymatic antioxidants cycle enzymes. The better performance of intercropping treatments i.e., IW and IM were also associated with improved osmolytes accumulation under rainfed conditions. As compared with control, N addition significantly improved the chlorophyll fluorescence, gas exchange traits, lipid peroxidation, and antioxidant enzyme activities under all intercropping treatments. Our results increase our understanding of the physiological, biochemical, and molecular mechanisms of intercropping-induced water stress tolerance in wheat and maize crops.

Enhancement of the Bioactive Compound Content and Antibacterial Activities in Curcuma Longa Using Zinc Oxide Nanoparticles

Incorporating nanoparticles into plant cultivation has been shown to improve growth parameters and alter the bioactive component compositions of many plant species, including Curcumin longa. The aim of the current study was to investigate the effects of foliar application of zinc oxide nanoparticles on the content of bioactive compounds and their antibacterial activities against potential bacterial pathogens. To this end, C. longa leaves were treated with different doses of ZnO NPs to see how this affected their bioactive component composition. The effect of different doses of ZnO NPs on the accumulation of bisdemethoxycurcumin, demethoxycurcumin, and curcumin in ethanolic extracts of C. longa rhizomes was evaluated using high-performance liquid chromatography (HPLC). When compared to the control treatment, foliar spraying with (5 and 40 mgL^-1) of ZnO NPs increased bisdemethoxycurcumin, demethoxycurcumin, and curcumin levels approximately (2.69 and 2.84)-, (2.61 and 3.22)-, and (2.90 and 3.45)-fold, respectively. We then checked whether the ethanolic extracts produced from the plantlets changed in terms of their phytochemical makeup and antibacterial properties. Furthermore, the results revealed that C. long-ZnO NPs displayed antibacterial activity against the tested S. aureus and P. aeruginosa bacterium strains, but had a few effect against E. coli. The MIC for P. aeruginosa was 100 g/mL. The time-kill studies also revealed that ZnO NPs at 4 MIC killed P. aeruginosa, Actinobacteria baumannii, and Bacillus sp. after 2 h, while S. aureus did not grow when treated with 4 × MIC of the extract for 6 h. The strongest antibacterial activity was seen in the extract from plantlets grown without nanoparticles for P. aeruginosa, whereas it was seen in the extract from plantlets grown in the presence of 5 mg/L ZnO NPs for E. coli, S. aureus, and P. aeruginosa. These findings show that ZnO NPs are powerful enhancers of bioactive compound production in C. longa, a trait that can be used to combat antibiotic resistance in pathogenic bacterial species.

Zn Supplementation Mitigates Drought Effects on Cotton by Improving Photosynthetic Performance and Antioxidant Defense Mechanisms

Drought is recognized as a paramount threat to sustainable agricultural productivity. This threat has grown more severe in the age of global climate change. As a result, finding a long-term solution to increase plants’ tolerance to drought stress has been a key research focus. Applications of chemicals such as zinc (Zn) may provide a simpler, less time-consuming, and effective technique for boosting the plant’s resilience to drought. The present study gathers persuasive evidence on the potential roles of zinc sulphate (ZnSO4·7H2O; 1.0 g Kg−1 soil) and zinc oxide (ZnO; 1.0 g Kg−1 soil) in promoting tolerance of cotton plants exposed to drought at the first square stage, by exploring various physiological, morphological, and biochemical features. Soil supplementation of ZnSO4 or ZnO to cotton plants improved their shoot biomass, root dry weight, leaf area, photosynthetic performance, and water-use efficiency under drought stress. Zn application further reduced the drought-induced accumulations of H2O2 and malondialdehyde, and electrolyte leakage in stressed plants. Antioxidant assays revealed that Zn supplements, particularly ZnSO4, reduced reactive oxygen species (ROS) accumulation by increasing the activities of a range of ROS quenchers, such as catalase, ascorbate peroxidase, glutathione S-transferase, and guaiacol peroxidase, to protect the plants against ROS-induced oxidative damage during drought stress. Increased leaf relative water contents along with increased water-soluble protein contents may indicate the role of Zn in improving the plant’s water status under water-deficient conditions. The results of the current study also suggested that, in general, ZnSO4 supplementation more effectively increased cotton drought tolerance than ZnO supplementation, thereby suggesting ZnSO4 as a potential chemical to curtail drought-induced detrimental effects in water-limited soil conditions.