Integrative application of heavy metal–resistant bacteria, moringa extracts, and nano-silicon improves spinach yield and declines its contaminant contents on a heavy metal–contaminated soil

Abstract

Microorganism-related technologies are alternative and traditional methods of metal recovery or removal. We identified and described heavy metal–resistant bacteria isolated from polluted industrial soils collected from various sites at a depth of 0–200 mm. A total of 135 isolates were screened from polluted industrial soil. The three most abundant isolate strains resistant to heavy metals were selected: Paenibacillus jamilae DSM 13815T DSM (LA22), Bacillus subtilis ssp. spizizenii DSM 15029T DSM (MA3), and Pseudomonas aeruginosa A07_08_Pudu FLR (SN36). A test was conducted to evaluate the effect of (1) isolated heavy metal–resistant bacteria (soil application), (2) a foliar spray with silicon dioxide nanoparticles (Si-NPs), and (3) moringa leaf extract (MLE) on the production, antioxidant defense, and physio-biochemical characteristics of spinach grown on heavy metal–contaminated soil. Bacteria and MLE or Si-NPs have been applied in single or combined treatments. It was revealed that single or combined additions significantly increased plant height, shoot dry and fresh weight, leaf area, number of leaves in the plant, photosynthetic pigments content, total soluble sugars, free proline, membrane stability index, ascorbic acid, relative water content, α-tocopherol, glycine betaine, glutathione, and antioxidant enzyme activities (i.e., peroxidase, glutathione reductase, catalase, superoxide dismutase, and ascorbate peroxidase) compared with the control treatment. However, applying bacteria or foliar spray with MLE or Si-NPs significantly decreased the content of contaminants in plant leaves (e.g., Fe, Mn, Zn, Pb, Cd, Ni, and Cu), malondialdehyde, electrolyte leakage, superoxide radical (O2·−), and hydrogen peroxide (H2O2). Integrative additions had a more significant effect than single applications. It was suggested in our study that the integrative addition of B. subtilis and MLE as a soil application and as a foliar spray, respectively, is a critical approach to increasing spinach plant performance and reducing its contaminant content under contaminated soil conditions.

Role of biochar in mitigating nickel stress in spinach (Spinacea oleracea L.) plants

“…In particular, Ni can become part of root cells after crossing the endodermal barrier and becomes deposited in the pericycle, thus, caused reduction in plant fresh and dry biomass (Yang et al 2017;Pipalde et al 2018). Moreover, Ni stress also blocks the proton pump which reduces the rate of cell division and cell elongation, which results in reduction of leaf area (Eltahawy et al 2022). However, application of BC reduced the toxic effects of Ni stress by improving length, fresh and dry weights of shoot and root and leaf area under Ni stress conditions.…”

Heavy Metal Resistant Bacteria in Rhizospheric Soil: A Review

“…isolated from Egyptian soils were also found to exhibit metal resistance genes. mer, chr, czc, ncc,cadA, cadB, cuoO, cuoP, golT etc. are some examples of bacterial genes responsible for metal resistance (Eltahawy et al, 2022).…”

“…Such accumulation causes serious abiotic stress that impairs human and animal health as well as soil biodiversity and lowers plant productivity. Due to heavy metal stress, there is an increase in reactive oxygen species, hydroxyl, superoxide radical and hydrogen peroxide production which are very harmful to plants (Eltahawy et al, 2022;Li et al, 2022).…”

Silicon nanoparticles in sustainable agriculture: synthesis, absorption, and plant stress alleviation

“…In agricultural practice, SiNPs can also be applied along with other plant growth regulators such as plant growth promoting rhizobacteria (PGPR), plant hormones, other NPs, and plant growth stimulating chemicals, which is more effective in enhancing plant abiotic stress resistance (Figure 5). As for PGPR, Eltahawy et al (2022) indicated that the integrated application of heavy metal-resistant bacteria and SiNPs more efficiently regulated antioxidant system and promoted spinach growth under metal contamination than individual application of SiNPs. In wheat grown under semi-arid condition, the combined treatment of SiNPs with CaCO 3 -precipitating bacteria induced more significant yield promotion than individual treatment with SiNPs or CaCO 3precipitating bacteria (Desoky et al, 2022).…”