A Multifactorial Approach to Untangle Graphene Oxide (GO) Nanosheets Effects on Plants: Plant Growth-Promoting Bacteria Inoculation, Bacterial Survival, and Drought

Abstract

Drought is a limiting factor for agricultural productivity. Climate change threatens to expand the areas of the globe subjected to drought, as well as to increase the severity and duration of water shortage. Plant growth-promoting bacteria (PGPB) are widely studied and applied as biostimulants to increase plant production and to enhance tolerance to abiotic and biotic constraints. Besides PGPB, studies on the potential of nanoparticles to be used as biostimulants are also thriving. However, many studies report toxicity of tested nanoparticles in bacteria and plants in laboratory conditions, but few studies have reported effects of nanoparticles towards bacterial cells and communities in the soil. The combined application of nanoparticles and PGPB as biostimulant formulations are poorly explored and it is important to unravel the potentialities of their combined application as a way to potentiate food production. In this study, Rhizobium sp. E20-8 and graphene oxide (GO) nanosheets were applied on container-grown maize seedlings in watered and drought conditions. Bacterial survival, seedling growth (dry weight), and biochemical endpoints (photosynthetic pigments, soluble and insoluble carbohydrates, proline, lipid peroxidation, protein, electron transport system, and superoxide dismutase) were evaluated. Results showed that the simultaneous exposure to GO and Rhizobium sp. E20-8 was able to alleviate the stress induced by drought on maize seedlings through osmotic and antioxidant protection by GO and mitigation of GO effects on the plant’s biochemistry by Rhizobium sp. E20-8. These results constitute a new lead on the development of biostimulant formulations to improve plant performance and increase food production in water-limited conditions.

Graphene Oxide, a Novel Nanomaterial as Soil Water Retention Agent, Dramatically Enhances Drought Stress Tolerance in Soybean Plants

“…Graphene oxide (GO), a novel nanomaterial as a soil water retention agent, plays a role in the growth and development of plants ( Shen et al, 2018 ; Xie et al, 2020 ). GO not only increased the drought tolerance of in Zea mays L. and Paeonia ostii ( Zhao et al, 2020 ; Lopes et al, 2021 ), but also enhanced the saline-alkali tolerance of Medicago sativa L. ( Chen et al, 2021 ). In addition, the previous studies showed that the surface morphology and internal structure of Paeonia ostii roots were not obviously different between GO and without GO treatment using SEM and TEM.…”

“…Recently, it has been found that GO as an effective soil water retention agent can confer drought stress tolerance to Paeonia ostii without causing toxicity ( Zhao et al, 2020 ). Furthermore, the effects of GO nanosheets were in a drought context, with the osmotic and antioxidant protection conferred by GO nanosheets to drought shoots, leading to higher shoot biomass ( Lopes et al, 2021 ). The findings indicated that GO might increase the drought tolerance of woody plants, but no research on the drought tolerance of soybean plants treated with GO has yet been undertaken.…”

Do Volatiles Affect Bacteria and Plants in the Same Way? Growth and Biochemical Response of Non-Stressed and Cd-Stressed Arabidopsis thaliana and Rhizobium E20-8

“…Plant and bacterial samples were extracted in 50 mM potassium phosphate buffer (pH 7.0): 300 μL for bacterial samples < 0.02 g, 600 μL for bacterial samples ≥ 0.02 g, and 600 μL for plant samples. Bacterial samples were sonicated and centrifuged as described in Matos et al (2019) [ 54 ]. Plant samples were homogenized with a pestle and mortar and centrifuged as described in Lopes et al (2021) [ 54 ].…”

“…Bacterial samples were sonicated and centrifuged as described in Matos et al (2019) [ 54 ]. Plant samples were homogenized with a pestle and mortar and centrifuged as described in Lopes et al (2021) [ 54 ]. The supernatant was collected in a new microtube and used immediately or stored at −80 °C for biochemical analysis.…”

Advances in Biologically Applicable Graphene-Based 2D Nanomaterials

“…E20-8 mitigated adverse impact of water deficit on plants, whereby GO ensured osmotic and antioxidant protection of plants, while Rhizobium sp. E20-8 alleviated negative impact of GO on biochemical processes of plants [ 248 ].…”