Muhammad Tariq Javed

Cadmium (Cd) poses serious threats to plant growth and development, whereas the use of plant growth-promoting rhizobacteria (PGPR) has emerged a promising approach to diminish Cd retention in crops. A pot experiment was conducted to evaluate the effect of Cd tolerant strain Acinetobacter sp. SG-5 on growth, phytohormonal response, and Cd uptake of two maize cultivars (3062 and 31P41) under various Cd stress levels (0, 5, 12, 18, 26, and 30 μM CdCl₂). The results revealed that CdCl₂ treatment significantly suppressed the seed germination and growth together with higher Cd retention in maize cultivars in a dose-dependent and cultivar-specific manner with pronounced negative effect in 31P41. However, SG-5 strain exerted positive impact by up-regulating seed germination traits, plant biomass, photosynthetic pigments, enzymatic and non-enzymatic antioxidants, endogenous hormone level indole-3-acetic acid (IAA), abscisic acid (ABA), and sustained optimal nutrient’s levels in both cultivars but predominantly in Cd-sensitive one (31P41). Further, Cd-resistant PGPR decreased the formation of reactive oxygen species in terms of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) verified through 3, 3′-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) analysis in conjunction with reduced Cd uptake and translocation in maize root and shoots in comparison to controls, advocating its sufficiency for bacterial-assisted Cd bioremediation. In conclusion, both SG-5 inoculated cultivars exhibited maximum Cd tolerance but substantial Cd tolerance was acquired by Cd susceptible cultivar-31P41 than Cd-tolerant one (3062). Current work recommended SG-5 strain as a promising candidate for plant growth promotion and bacterial-assisted phytomanagement of metal-polluted agricultural soils.

During current times, the use of bio-colorants attained public acceptance as a sustainable alternative to synthetic ones which in turn reduced the environmental contamination. The present study focused on the green, safe, and clean technology for the resurgence of natural colorant from cocklebur (Xanthium strumarium L.) leaves and their application to cotton fabric. Natural colorants were extracted by employing an eco-friendly microwave-assisted extraction process using an aqueous and alkaline medium. Dyeing of cotton fabric was carried out using irradiated and unirradiated cotton fabric with irradiated and unirradiated natural dyes of cocklebur leaves. The results of extraction experiments revealed that 4 min microwave-assisted alkaline extract exhibited significantly outstanding color strength onto microwave-treated cotton fabric compared to aqueous one. Further to investigate the optimum dyeing conditions for cotton fabric, various dyeing variables such as dyeing time, dyeing temperature, dye concentration, and exhausting agent were monitored and found a superior result using a dye concentration of 45 ml, for dyeing cotton fabric at 75 °C for 50 min in the presence of 4 g/100 ml of table salt. For improvement in color strength and color fastness properties, the effects of various bio-mordants, such as eucalyptus bark, acacia bark, turmeric rhizome, and onion shells, and chemical mordants (aluminum and copper) on dyed cotton fabric were also evaluated. It was also observed that cotton fabric dyed with alkaline extract of cocklebur leaves using bio-mordants as pre-mordants (4% acacia, 4% eucalyptus, 2% onion) and post-mordants (3% onion, 3% eucalyptus, 4% acacia) exhibited the highest color strength and various hues with acceptable colorfastness properties against light, washing, and rubbing in comparison to chemical mordants. The ISO standard for fastness also revealed that bio-mordanting has enhanced the rating from good to excellent in comparison to chemical mordants. The results provide ample scope for the extraction of yellow natural dye from the cocklebur leaves for eco-friendly coloration of fabrics using bio-mordants.

Metal retention in wastewater fertigated crops poses a potential hazard to food chain. Current work demonstrates the bioremediation and growth-promoting potential of Acinetobacter schindleri SR-5–1 by using nitrogen-fixing (pea) and non-nitrogen fixing (linseed) plants under cadmium (Cd) and wastewater irrigation regimes. Both plants were grown at 250 or 500 CdCl₂ and 75 or 100% wastewater, each separately with and without A. schindleri SR-5–1 inoculation. The results revealed that Cd and wastewater significantly decreased growth, biomass, antioxidants, and nutrient acquisition through increased malondialdehyde, H₂O₂, and Cd accumulation. However, application of A. schindleri SR-5–1 significantly promoted morpho-physio-biochemical attributes while diminishing MDA and H₂O₂ under applied Cd and wastewater stress levels in both pea and linseed. Further, PGPR inoculation positively influenced pea and linseed seedlings through a substantial decline in Cd accumulation in roots/shoots and retained the optimal level of essential nutrients. It was inferred that both pea and linseed, with A. schindleri SR-5–1 application, exhibited higher growth and metabolism under Cd and wastewater stress but substantial tolerance was acquired under wastewater stress. Studied plants exhibited tolerance in order of 75% WW ≥ 250 µM Cd ≥ 100%WW ≥ 500 µM Cd treatment under A. schindleri inoculation. Current findings revealed the potential of A. schindleri to be exploited both for bioremediation and bio-fertilization under Cd, and wastewater-polluted regimes to reduce metal contamination of edible plants. It was suggested that with inoculation of A. schindleri SR-5–1, 75% WW dilution can be applied for irrigation of both nitrogen-fixing and non-nitrogen-fixing crops.

Cadmium (Cd) being a non-essential, mobile, and toxic heavy metal, negatively affects the plant growth and physiology. Current work investigated the impact of Serratia marcescens CP-13 inoculation on root organic acids and nutrient exudates of two maize cultivars varying in Cd tolerance under induced Cd toxicity. Seedlings of Cd-sensitive (Sahiwal-2002) and Cd-tolerant (MMRI-Yellow) cultivars were grown either inoculated or non-inoculated with CP-13 in Petri plates having various Cd stress levels (0, 6, 12, 18, 24, 30 μM). Seedlings were transferred to rhizoboxes for the collection of root exudates and analysis of physio-biochemical traits. Both maize cultivars exuded higher organic acids and nutrient exudates under non-inoculated conditions as compared to inoculated ones. Non-inoculated tolerant cultivar exhibited higher nutrient accumulation, biomass, antioxidants, total chlorophyll, Cd release meanwhile reduced Cd uptake, lipid peroxidation, exudation of organic acids, and nutrients than the sensitive one. However, under CP-13 inoculation, Cd sensitive cultivar exhibited less exudation of organic acids (citric acid, acetic acid, malic acid, glutamic acid, formic acid, succinic acid, and oxalic acid), nutrients mobilization (K, Na, Zn, Ca, and Mg), total chlorophyll, antioxidants (APX, SOD, POD), total soluble sugar, diminished MDA, and Cd uptake. The significant reduction in release of root exudates by both cultivars was likely due to the plant growth promoting traits of CP-13 which confer Cd tolerance. The maximum release of rhizospheric root exudates were documented at 30 μM applied Cd stress. Therefore, the Serratia sp. CP-13 was proposed as a potential inoculant for bioremediation of Cd together with maize cultivars.

Chloride is an essential nutrient for plants, but high concentrations can be harmful. Silicon ameliorates both abiotic and biotic stresses in plants, but it is unknown if it can prevent cellular increase of chloride. Therefore, we investigated the influx of Cl⁻ ions in two wheat cultivars different in salt sensitivity, by epifluorescence microscopy and a highly Cl⁻-sensitive dye, MQAE, N-[ethoxycarbonylmethyl]-6-methoxy-quinolinium bromide, in absence and presence of potassium silicate, K₂SiO₃. The Cl⁻-influx was higher in the salt-sensitive cv. Vinjett, than in the salt-tolerant cv. S-24, and silicate pre-treatment of protoplasts inhibited the Cl⁻-influx in both cultivars, but more in the sensitive cv. Vinjett. To investigate if the Cl⁻-transporters TaCLC1 and TaNPF2.4/2.5 are affected by silicate, expression analyses by RT-qPCR were undertaken of TaCLC1 and TaNPF 2.4/2.5 transcripts in the absence and presence of 100 mM NaCl, with and without the presence of K₂SiO₃. The results show that both transporter genes were expressed in roots and shoots of wheat seedlings, but their expressions were differently affected by silicate. The TaNPF2.4/2.5 expression in leaves was markedly depressed by silicate. These findings demonstrate that less chloride accumulates in the cytosol of leaf mesophyll by Si treatment and increases salt tolerance.