Biological silicon nanoparticles improve Phaseolus vulgaris L. yield and minimize its contaminant contents on a heavy metals-contaminated saline soil

The synthesis of biological silicon nano-particles(Bio-Si-NPs)is an eco-friendly and lowcost method.There is no study focusing on the effect of Bio-Si-NPs on the plants grown on saline soil contaminated with heavy metals.In this study,an attempt was made to synthesis Bio-Si-NPs using potassium silica florid substrate,and the identified Aspergillus tubingensis AM11 isolate that separated from distribution systems of the potable water.A twoyear field trial was conducted to compare the protective effects of Bio-Si-NPs(2.5 and 5.0 mmol/L)and potassium silicate(10 mmol/L)as a foliar spray on the antioxidant defense system,physio-biochemical components,and the contaminants contents of Phaseolus vulgaris L.grown on saline soil contaminated with heavy metals.Our findings showed that all treatments of Bio-Si-NPs and potassium silicate significantly improved plant growth and production,chlorophylls,carotenoids,transpiration rate,net photosynthetic rate,stomatal conductance,membrane stability index,relative water content,free proline,total soluble sugars,N,P,K,Ca2+,K+/Na+,and the activities of peroxidase,catalase,ascorbic peroxidase and superoxide oxide dismutase.Application of Bio-Si-NPs and potassium silicate significantly decreased electrolyte leakage,malondialdehyde,H2 O2,O2·-,Na+,Pb,Cd,and Ni in leaves and pods of Phaseolus vulgaris L.compared to control.Bio-Si-NPs were more effective compared to potassium silicate.Application of Bio-Si-NPs at the rate of 5 mmol/L was the recommended treatment to enhance the performance and reduce heavy metals content on plants grown on contaminated saline soils.

Spirulina platensis extract improves the production and defenses of the common bean grown in a heavy metals-contaminated saline soil

Plants have to cope with several abiotic stresses,including salinity and heavymetals(HMs).Under these stresses,several extracts have been used as effective natural biostimulants,however,the use of Spirulina platensis(SP)extract(SPE)remains elusive.The effects of SPE were evaluated as soil addition(SA)and/or foliar spraying(FS)on antioxidant defenses and HMs content of common bean grown in saline soil contaminated with HMs.Individual(40 or 80 mg SPE/hill added as SA or 20 or 40 mg SPE/plant added as FS)or integrative(SA+FS)applications of SPE showed significant improvements in the following order:SA-80+FS-40>SA-80+FS-20>SA-40+FS-40>SA-40+FS-20>SA-80>SA-40>FS-40>FS-20>control.Therefore,the integrative SA+FS with 40 mg SP/plant was the most effective treatment in increasing plant growth and production,overcoming stress effects and minimizing contamination of the edible part.It significantly increased plant growth(74%–185%)and yield(107%–227%)by enhancing net photosynthetic rate(78.5%),stomatal conductance(104%),transpiration rate(124%),and contents of carotenoids(60.0%),chlorophylls(49%–51%),and NPK(271%–366%).These results were concurrent with the marked reductions in malondialdehyde(61.6%),hydrogen peroxide(42.2%),nickel(91%–94%),lead(80%–9%),and cadmium(74%–91%)contents due to the improved contents of glutathione(87.1%),ascorbate(37.0%),andα-tocopherol(77.2%),and the activities of catalase(18.1%),ascorbate peroxidase(18.3%),superoxide dismutase(192%),and glutathione reductase(52.2%)as reinforcing mechanisms.Therefore,this most effective treatment is recommended to mitigate the stress effects of salinity and HMs on common bean production while minimizing HMs in the edible part.