Green Synthesis of Iron Oxide (Hematite) Nanoparticles and Their Influence on Sorghum bicolor Growth under Drought Stress

Abstract

Drought is a major abiotic stress that confronts plant growth and productivity, thus compromising food security. Plants use physiological and biochemical mechanisms to cope with drought stress, but at the expense of growth. Green-synthesized nanoparticles (NPs) have gained great attention in agriculture due to their environmental friendliness and affordability while serving as potential biofertilizers. This study investigates the role of hematite (αFe2O3) NPs, synthesized from Aspalathus linearis (rooibos), to improve Sorghum bicolor growth under drought stress. About 18 nm, spherical, and highly agglomerated hematite (αFe2O3) NPs were obtained. Sorghum seeds were primed with 5, 10, and 15 mg/L αFe2O3 NPs, and, after seven days of germination, the seedlings were transferred into potting soil, cultivated for fourteen days, and were subsequently water deprived (WD) for a further seven days. A reduction in plant height (78%), fresh (FW; 35%) and dry (DW; 36%) weights, and chlorophyll (chl) content ((total chl (81%), chla (135%), and chlb (1827%)) was observed in WD plants, and this correlated with low nutrients (Mg, Si, P, and K) and alteration in the anatomic structure (epidermis and vascular bundle tissues). Oxidative damage was observed as deep blue (O2●−) and brown (H2O2) spots on the leaves of WD plants, in addition to a 25% and 40% increase in oxidative stress markers (H2O2 and MDA) and osmolytes (proline and total soluble sugars), respectively. Seed priming with 10 mg/L αFe2O3 NPs improved plant height (70%), FW (56%), DW (34%), total Chl (104%), chla (160%) and chlb (1936%), anatomic structure, and nutrient distribution. Priming with 10 mg/L αFe2O3 NPs also protected sorghum plants from drought-induced oxidative damage by reducing ROS formation and osmolytes accumulation and prevented biomolecule degradation. The study concludes that green synthesized hematite NPs positively influenced sorghum growth and prevented oxidative damage of biomolecules by improving nutrient uptake and osmoregulation under drought stress.

Seed Priming with MeJa Prevents Salt-Induced Growth Inhibition and Oxidative Damage in Sorghum bicolor by Inducing the Expression of Jasmonic Acid Biosynthesis Genes

“…Over-accumulation of hydrogen peroxide (H 2 O 2 ) was determined by histochemical staining based on its role in oxidizing 3,3 -diaminobenzidene (DAB) in a reaction induced by horseradish peroxidase to form brown formazan at the location of enzyme activity [56]. Hydrogen peroxide localization was determined in the leaves as previously described [12,95]. Briefly, leaves were submerged in 1 mg/mL 3 ,3 diaminobenzidine (DAB), pH 3.8, for 12 h at 25 • C while concealed from light.…”

“…Lipid peroxidation is indicative of the oxidation of unsaturated fatty acids in the cell membrane, whereby malondialdehyde (MDA) is produced as a by-product [12,96]. Malondialdehyde accumulation was selected as a biomarker of lipid peroxidation in this study, following the traditional thiobarbituric acid (TBA) reaction method to measure MDA content as previously determined with slight modifications [97].…”

“…The anatomic structure, including the epidermis, xylem, and element distribution, was analyzed at the University of the Western Cape using high-resolution scanning electron microscopy (HRSEM) as described previously [12,37,64]. Microphotographs were taken to obtain the morphological characteristics using the Tescan MIRA field emission gun scanning electron microscope using an in-lens secondary electron detector and set to an operating acceleration voltage of 5 kV.…”

“…•− ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical ( • HO), cause damage to lipids, proteins, carbohydrates, and nucleic acids when produced in high concentrations [11,12]. Malondialdehyde (MDA) is one of the major products of lipid peroxidation and has therefore been extensively accepted as an oxidative stress marker and for assaying the level of lipid peroxidation [13].…”

Green iron oxide nanoparticles and magnetic nanobiochar: enhancing tomato performance, phytochemicals, and root-knot nematode resistance

“…So, the green synthesis of nanoparticles is the preferred technique for treating plant diseases because of its low levels of toxicity, low production cost, and ability to improve plant growth [ 11 – 14 ]. Green hematite nanoparticles improved the uptake of nutrients, sorghum growth, and osmoregulation in drought-stressed plants by reducing oxidative damage to biomolecules [ 15 ]. Iron is a critical component of cellular redox processes, acting as a precursor for anti-oxidative enzymes like catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), as well as a scavenger of ROS [ 16 ].…”