Malachite green (MG) dye is a common environmental pollutant that threatens human health and the integrity of the Earth’s ecosystem. The aim of this study was to investigate the potential biodegradation of MG dye by actinomycetes species isolated from planted soil near an industrial water effluent in Cairo, Egypt. The Streptomyces isolate St 45 was selected according to its high efficiency for laccase production. It was identified as S. exfoliatus based on phenotype and 16S rRNA molecular analysis and was deposited in the NCBI GenBank with the gene accession number OL720220. Its growth kinetics were studied during an incubation time of 144 h, during which the growth rate was 0.4232 (µ/h), the duplication time (td) was 1.64 d, and multiplication rate (MR) was 0.61 h, with an MG decolorization value of 96% after 120 h of incubation at 25 °C. Eleven physical and nutritional factors (mannitol, frying oil waste, MgSO₄, NH₄NO₃, NH₄Cl, dye concentration, pH, agitation, temperature, inoculum size, and incubation time) were screened for significance in the biodegradation of MG by S. exfoliatus using PBD. Out of the eleven factors screened in PBD, five (dye concentration, frying oil waste, MgSO₄, inoculum size, and pH) were shown to be significant in the decolorization process. Central composite design (CCD) was applied to optimize the biodegradation of MG. Maximum decolorization was attained using the following optimal conditions: food oil waste, 7.5 mL/L; MgSO₄, 0.35 g/L; dye concentration, 0.04 g/L; pH, 4.0; and inoculum size, 12.5%. The products from the degradation of MG by S. exfoliatus were characterized using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results revealed the presence of several compounds, including leuco-malachite green, di(tert-butyl)(2-phenylethoxy) silane, 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,4-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,2-benzenedicarboxylic acid, di-n-octyl phthalate, and 1,2-benzenedicarboxylic acid, dioctyl ester. Moreover, the phytotoxicity, microbial toxicity, and cytotoxicity tests confirmed that the byproducts of MG degradation were not toxic to plants, microbes, or human cells. The results of this work implicate S. exfoliatus as a novel strain for MG biodegradation in different environments.

Background: Abiotic stresses, like drought, are the major cause of shrinking plant, growth crop yields and quality. Nanotechnology has provided a significant improvement in increasing plant growth and yield of crops under stress conditions. This work assessed the potential of silicon for mitigating the negative effects of drought against wheat. In completely randomized design with three replicates, wheat seedlings grown under three watering levels (100, 60 and 40% of water holding capacity) were treated by silicon dioxide (SiO₂) as a normal or bulk form (Si) and SiO₂ nanoparticles (SiNPs) with concentrations of 100 and 200 mg L⁻¹. SiNPs was extracted from rice husk. Results: Si and SiNPs treatments are shown to improve the growth of plants and increase the shoots and root weight, relative water content, photosynthetic pigments, and proline in wheat. SiO₂ either normal or nanoparticles at 100 mg L⁻¹ decreased lipid peroxidation as malondialdehyde was reduced. Also, nano-silicon increased free amino acids, antioxidant enzymes while decreased soluble sugars. Cytotoxicity assay proved the safety of nano-silicon usage. Conclusions: In conclusion, the present study documented the significance of rice husk-extracted nano-silicon at rate of 100 mg L⁻¹ for improving growth and increasing tolerance to drought in wheat grown under water deficit.

Salinity stress has become a major threat to worldwide crop production. Exogenous melatonin (MT) has appeared as a promising treatment against salt stress in several plant species. However, MT effect on the tolerance of sorghum plants under different saline conditions (moderate and severe) remains ambiguous. This study was carried out to explore the impact of MT (0, 50, 100 and 200 µM) as a foliar application on sorghum seedlings grown under moderate and severe saline conditions using sodium chloride, NaCl (75 and 150 µM NaCl). Salinity treatments were applied as solution in sand medium in pots. The results demonstrated that rising salinity level negatively affected plant growth, photosynthetic pigments (chlorophylls and carotenoids), leaf water status and ionic homeostasis (sodium, potassium, and calcium ions). Applied-MT specifically at 100 or 200 µM enhanced the osmotic balance, cell membrane stabilizing and leaf relative water content. These effects were associated with an obvious restriction to the level of hydrogen peroxide, lipid peroxidation (malondialdehyde content) and methylglyoxal. Moreover, antioxidant activities of peroxidase, catalase, superoxide dismutase, and ascorbate peroxidase enzymes were modulated by MT treatments. Molecular docking modeling assessment illustrated top-ranked confirmations between MT and the target antioxidant enzymes. MT forms multiple hydrogen bonds with key amino acid residues for glycine (A: 162), tryptophan (A: 41), leucine (A: 165), tyrosine (A: 235) in the active site of ascorbate peroxidase. The alkyl interactions with leucine (A: 37), arginine (A: 38) and cysteine (A: 168) also contribute to its high affinity. Despite sorghum plant is commonly moderately tolerant to salinity stress, the results of this study confirmed its high sensitivity to a wide range of saline conditions at early growth stages. Melatonin spraying led to improvements in various morphological, physiological and biochemical mechanisms that harmonized together to confer stress resistance to salt-stressed sorghum seedlings.

Table grape berries are classified as a perishable crop that deteriorates quickly after harvest. The application of melatonin after harvest was found to be effective for retarding senescence and slowing ripening. In the current study, we tested the influence of two melatonin concentrations (50 and 100 µmol) as a postharvest application on quality, bioactive compounds, and enzyme activities of grape berries cv “Crimson” stored at 0 ± 1 °C and 90% relative humidity (RH) for 35 days. Our results indicated that melatonin application extends the shelf-life of berries by reducing weight loss and maintaining total soluble solids (TSS), titratable acidity (TA), berry adherence strength, and firmness. Melatonin treatment also reduced pectin methyl esterase (PME) and polygalactouranase (PG) enzyme activities compared to the control. Moreover, O₂^•− and H₂O₂ rates in berries were reduced by high melatonin concentration. Moreover, peroxidase (POD) and catalase (CAT) enzyme activities were increased by melatonin application. Our findings suggested using melatonin postharvest to increase shelf life and maintain quality attributes during refrigerated storage, which could be advantageous on a large scale.

The two-spotted spider mite, Tetranychus urticae, also known as the red spider, is one of the most harmful pests in agriculture and causes large losses of many crops. These mites have rapidly developed a resistance to many chemical pesticides in recent years. In this study, the essential oil of seeds of the anise plant (Pimpinella anisum) was extracted by hydrodistillation, and the chemical composition of the oil was analyzed. The antioxidant activity of the volatile oil was determined by the DPPH radical scavenging assay. The acaricidal activity of the anise oil, a natural acaricide, was evaluated for its ability to protect green bean plants from mite injury. The two-spotted spiders were spread on green bean seedlings for 1 week; then, different plants were sprayed with different concentrations of anise oil (10, 20, 30, or 40 µL/L). Our results revealed that anethole was the major component of anise oil, at 53.23%. The acaricidal effect of the various concentrations on T. urticae was recorded after 24, 48, and 72 h of treatment. Our findings suggest that anise oil showed significant acaricidal activity against T. urticae in a dose- and time-dependent manner. Anise oil at a concentration of 40 µL/L killed 96.0% of the red spiders after 72 h. Also, all concentrations of anise oil inhibited acetylcholinesterase, and the spiders’ protease activity declined when the plants were treated with 30 or 40 µL/L of anise oil. The concentrations of 10 and 20 µL/L did not significantly affect the protease activity of T. urticae mites. We can conclude that anise oil exhibited acaricidal activity against T. urticae and that this was highly correlated with the inhibition of acetylcholinesterase and protease activities in the mites.

Salinization, as a serious climate change phenomenon, continues to cause critical issues for soils and crops. Abundance of genetic diversity of plants could contribute in solving the impacts of salinity. However, the relations between physiological and molecular traits of plant species need deep investigation and interpretation. Pot experiments were conducted in the greenhouse to investigate the difference in behavior between two amaranth species when they were beforehand subjected to salinity-stress conditions, specifically on some specific physiological and molecular characteristics. After 45 days from transplanting, salt stress was induced using a 150 mM sodium chloride solution. Treatments were arranged in randomized complete block design using three replications. After 0, 2, 6, 10, and 24 h, samples were collected to evaluate physiological data as well as diversity of gene expression. The samples were immediately frozen in liquid nitrogen and stored in -80⁰ C ultralow temperature refrigerators. Findings revealed that the red amaranth species (Amaranthus cruentus) was more tolerant to saline stress than the green amaranth species (Amaranthus hypochondriacus). Result data revealed that malondialdehyde (MDA) content in the red amaranth increased after 2 h then decreased (after 6 and 10 h) before rising again after 24 h. In the green amaranth, MDA content initially decreased after 2 h before increasing and later decreasing in a zigzag pattern ending in an increase after 24 h. There was an initial steep rise in proline content of green amaranth after 2 h which continued to still rise moderately till 24 h. In the red amaranth the initial rise in proline continued after 2, 6 and 10 h before it stopped. Results also showed that red amaranth gave higher value of superoxide dismutase (SOD) activity as compared with green amaranth in all tested salinity exposure times. The investigation on the expression of four genes assessed through quantitative PCR indicated the efficiency of red amaranth in increasing the expression of SOS1, HKT1, NHX1, and DGR2 genes, which encode adaptation-related proteins under salinity stress. In summary, the current work demonstrated that red amaranth could be an efficient genetic resource in improving salt-tolerant genotypes belonging to Amaranthus genus.