Synergistic Effects of Kaolin and Silicon Nanoparticles for Ameliorating Deficit Irrigation Stress in Maize Plants by Upregulating Antioxidant Defense Systems.

Water deficit is a significant environmental stress that has a negative impact on plant growth and yield. In this research, the positive significance of kaolin and SiO2 nanoparticles in moderating the detrimental effects of water deficit on maize plant growth and yield is investigated. The foliar application of kaolin (3 and 6%) and SiO2 NPs (1.5 and 3 mM) solutions increased the growth and yield variables of maize plants grown under normal conditions (100% available water) and drought stress conditions (80 and 60% available water (AW)). In addition, plants treated with SiO2 NPs (3 mM) demonstrated increased levels of important osmolytes, such as proline and phenol, and maintained more of their photosynthetic pigments (net photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E)) than with other applied treatments under either stress or non-stress conditions. Furthermore, the exogenous foliar application of kaolin and SiO2 NPs also reduced the amounts of hydroxyl radicals (OH), superoxide anions (O2), hydrogen peroxide (H2O2), and lipid peroxidation in maize plants experiencing a water deficit. In contrast, the treatments led to an increase in the activity of antioxidant enzymes such as peroxidase (POX), ascorbate peroxidase (APX), glutathione peroxidase (GR), catalase (CAT), and superoxide dismutase (SOD). Overall, our findings indicate the beneficial impact of the application of kaolin and silicon NPs, particularly the impact of SiO2 NPs (3 mM) on managing the negative, harmful impacts of soil water deficit stress in maize plants.

Alleviation of Cadmium and Nickel Toxicity and Phyto-Stimulation of Tomato Plant L. by Endophytic Micrococcus luteus and Enterobacter cloacae.

Cadmium (Cd) and nickel (Ni) are two of the most toxic metals, wreaking havoc on human health and agricultural output. Furthermore, high levels of Cd and Ni in the soil environment, particularly in the root zone, may slow plant development, resulting in lower plant biomass. On the other hand, endophytic bacteria offer great promise for reducing Cd and Ni. Moreover, they boost plants' resistance to heavy metal stress. Different bacterium strains were isolated from tomato roots. These isolates were identified as Micrococcus luteus and Enterobacter cloacae using 16SrDNA and were utilized to investigate their involvement in mitigating the detrimental effects of heavy metal stress. The two bacterial strains can solubilize phosphorus and create phytohormones as well as siderophores. Therefore, the objective of this study was to see how endophytic bacteria (Micrococcus luteus and Enterobactercloacae) affected the mitigation of stress from Cd and Ni in tomato plants grown in 50 µM Cd or Ni-contaminated soil. According to the findings, Cd and Ni considerably lowered growth, biomass, chlorophyll (Chl) content, and photosynthetic properties. Furthermore, the content of proline, phenol, malondialdehyde (MDA), H2O2, OH, O2, the antioxidant defense system, and heavy metal (HM) contents were significantly raised under HM-stress conditions. However, endophytic bacteria greatly improved the resistance of tomato plants to HM stress by boosting enzymatic antioxidant defenses (i.e., catalase, peroxidase, superoxide dismutase, glutathione reductase, ascorbate peroxidase, lipoxygenase activity, and nitrate reductase), antioxidant, non-enzymatic defenses, and osmolyte substances such as proline, mineral content, and specific regulatory defense genes. Moreover, the plants treated had a higher value for bioconcentration factor (BCF) and translocation factor (TF) due to more extensive loss of Cd and Ni content from the soil. To summarize, the promotion of endophytic bacterium-induced HM resistance in tomato plants is essentially dependent on the influence of endophytic bacteria on antioxidant capacity and osmoregulation.