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.

Impact of titanium dioxide (TiO2) nanoparticle and liquid leachate of mushroom compost on agronomic and biochemical response of marigold (Tagetes erecta L.) under saline stress.

The cultivation of ornamental horticultural crops under salinity stress has been a challenge for growers all over the world. In this study, an attempt was made for pot cultivation of Marigold (Tagetes erecta L. var. Pusa Basanti Gainda) in salt-stressed (SS) soil (150 mM) with the combined use of mushroom compost leachate (CL) and foliar application of titanium dioxide nanoparticles (TiO2-NPs). For this purpose, a total of six pot treatments, i.e., borewell water (BW; control), T1 (BW with SS), T2 (BW with SS and TiO2-NPs), T3 (CL supplemented), T4 (CL with SS), and T5 (CL with SS and TiO2-NPs) were conducted in triplicate. The results of this study showed that CL supplementation significantly (p < 0.05) improved the physicochemical i.e., pH (14.5%), electrical conductivity (32.9%), total nitrogen (27.4%), total phosphorus (247.6%)), and nutrient (organic matter: 119.6%) profiles of soil which later helped in higher growth (30-35%) and yield (5.4-40.7%) of T. erecta. In CL-based treatments, the biochemical constituents were significantly (p < 0.05) higher than those in BW-irrigated ones. Also, the levels of selected stress defense enzymes were significantly increased under SS treatment but reduced under TiO2-NP application. Overall, it was observed that the combined application of CL and TiO2-NPs (T5 treatment) was the most helpful treatment for enhanced germination, growth, yield, biochemical parameters, and better plant enzymatic activities to cope with saline stress. This study provides a mechanistic understanding of T. erecta plants under saline stress which is crucial for the development of targeted interventions aimed at improving plant tolerance to saline conditions.

Co-application of titanium nanoparticles and melatonin effectively lowered chromium toxicity in lemon balm (Melissa officinalis L.) through modifying biochemical characteristics.

Chromium (Cr) toxicity can negatively affect plant growth and development, impacting agricultural productivity and posing risks to human health. Metallic nanoparticles (MNPs) such as titanium dioxide (TiO2) and natural growth regulators such as melatonin (MT) become a promising technology to manage heavy metal-contaminated soils and promote safe food production. The present work was conducted to find the effect of foliar application of TiO2 NPs (15 mg L-1) and MT (100 µM) on growth, biochemical attributes, and Cr accumulation in plant tissues of Melissa officinalis L. under Cr toxicity (50 and 100 mg Cr kg-1 soil). The results showed that Cr toxicity led to decreased plant performance, where 100 mg Cr kg-1 soil led to notable decreases in shoot weight (28%), root weight (27%), essential oil (EO) yield (34%), chlorophyll (Chl) a + b (33%), while increased malondialdehyde (MDA, 30%), superoxide dismutase (SOD) activity (51%), and catalase (CAT) activity (122%). The use of TiO2 NPs and MT, particularly their co-application, remarkably reduced Cr toxicity by enhancing plant weight, Chl content, and lowered MDA and antioxidant activity. Total phenolic content (TPC), total flavonoid content (TFC), EO percentage, and rosmarinic acid in plants treated with Cr at 50 mg Cr kg-1 soil and co-application of TiO2 NPs and MT were relatively higher than in other treatments. Under 100 mg Cr kg-1 soil, the synergic effect of TiO2 NPs and MT-enhanced rosmarinic acid content (22%) but lowered Cr accumulation in roots (51%) and shoots (72%). Heat map analysis showed that CAT, SOD, MDA, and EO yield had the maximum variability under Cr, TiO2 NPs, and MT. Exogenous TiO2 NPs and MT can be recommended to modulate Cr toxicity in lemon balm under soil Cr toxicity.

An experimental and prediction modeling study on water lettuce (Pistia stratiotes L.) assisted heavy metals removal from glass industry effluent.

The glass manufacturing industry produces hazardous effluent that is difficult to manage and causes numerous environmental problems when disposed of in the open. In this study, an attempt was made to study the phytoremediation feasibility of water lettuce (Pistia stratiotes L.), a free-floating aquatic macrophyte, for the removal of six heavy metals from glass industry effluent (GIE) at varying concentrations (0, 25, 50, 75, and 100%). After a 40-day experiment, the results showed that 25% GIE dilution showed maximum removal of heavy metals i.e., Cu (91.74%), Cr (95.29%), Fe (86.47%), Mn (92.95%), Pb (87.10%), and Zn (91.34%), respectively. The bioaccumulation, translocation, and Pearson correlation studies showed that the amount of heavy metals absorbed by vegetative parts of P. stratiotes was significantly correlated with concentrations. The highest biomass production, chlorophyll content, relative growth rate, and biomass productivity were also noted in the 25% GIE treatment. Moreover, the multiple linear regression models developed for the prediction of heavy metal uptake by P. stratiotes also showed good performance in determining the impact of GIE properties. The models showed a high coefficient of determination (R2 > 0.99), low mean average normalizing error (MANE = 0.01), and high model efficiency (ME > 0.99) supporting the robustness of the developed equations. This study outlined an efficient method for the biological treatment of GIE using P. stratiotes to reduce risks associated with its unsafe disposal.

Biological Applications of Ball-Milled Synthesized Biochar-Zinc Oxide Nanocomposite Using Zea mays L.

Nanotechnology is one of the vital and quickly developing areas and has several uses in various commercial zones. Among the various types of metal oxide-based nanoparticles, zinc oxide nanoparticles (ZnO NPs) are frequently used because of their effective properties. The ZnO nanocomposites are risk-free and biodegradable biopolymers, and they are widely being applied in the biomedical and therapeutics fields. In the current study, the biochar-zinc oxide (MB-ZnO) nanocomposites were prepared using a solvent-free ball-milling technique. The prepared MB-ZnO nanocomposites were characterized through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray powder diffraction (XRD), and thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and ultraviolet-visible (UV) spectroscopy. The MB-ZnO particles were measured as 43 nm via the X-ray line broadening technique by applying the Scherrer equation at the highest peak of 36.36°. The FTIR spectroscope results confirmed MB-ZnO's formation. The band gap energy gap values of the MB-ZnO nanocomposites were calculated as 2.77 eV by using UV-Vis spectra. The MB-ZnO nanocomposites were tested in various in vitro biological assays, including biocompatibility assays against the macrophages and RBCs and the enzymes' inhibition potential assay against the protein kinase, alpha-amylase, cytotoxicity assays of the leishmanial parasites, anti-inflammatory activity, antifungal activity, and antioxidant activities. The maximum TAC (30.09%), TRP (36.29%), and DPPH radicals' scavenging potential (49.19%) were determined at the maximum dose of 200 µg/mL. Similarly, the maximum activity at the highest dose for the anti-inflammatory (76%), at 1000 µg/mL, alpha-amylase inhibition potential (45%), at 1000 µg/mL, antileishmanial activity (68%), at 100 µg/mL, and antifungal activity (73 ± 2.1%), at 19 mg/mL, was perceived, respectively. It did not cause any potential harm during the biocompatibility and cytotoxic assay and performed better during the anti-inflammatory and antioxidant assay. MB-ZnO caused moderate enzyme inhibition and was more effective against pathogenic fungus. The results of the current study indicated that MB-ZnO nanocomposites could be applied as effective catalysts in various processes. Moreover, this research provides valuable and the latest information to the readers and researchers working on biopolymers and nanocomposites.

First Report of Fruit Rot of Cherry and Its Control Using Fe2O3 Nanoparticles Synthesized in Calotropis procera.

Cherry is a fleshy drupe, and it is grown in temperate regions of the world. It is perishable, and several biotic and abiotic factors affect its yield. During April-May 2021, a severe fruit rot of cherry was observed in Swat and adjacent areas. Diseased fruit samples were collected, and the disease-causing pathogen was isolated on PDA. Subsequent morphological, microscopic, and molecular analyses identified the isolated pathogen as Aspergillus flavus. For the control of the fruit rot disease of cherry, iron oxide nanoparticles (Fe2O3 NPs) were synthesized in the leaf extract of Calotropis procera and characterized. Fourier transform infrared (FTIR) spectroscopy of synthesized Fe2O3 NPs showed the presence of capping and stabilizing agents such as alcohols, aldehydes, and halo compounds. X-ray diffraction (XRD) analysis verified the form and size (32 nm) of Fe2O3 NPs. Scanning electron microscopy (SEM) revealed the spinal-shaped morphology of synthesized Fe2O3 NPs while X-ray diffraction (EDX) analysis displayed the occurrence of main elements in the samples. After successful preparation and characterization of NPs, their antifungal activity against A. flavus was determined by poison technique. Based on in vitro and in vivo antifungal activity analyses, it was observed that 1.0 mg/mL concentration of Fe2O3 can effectively inhibit the growth of fungal mycelia and decrease the incidence of fruit rot of cherry. The results confirmed ecofriendly fungicidal role of Fe2O3 and suggested that their large-scale application in the field to replace toxic chemical fungicides.