ORIGINAL ARTICLE

Enhancing quinoa’s photosynthetic capacity under high NaCl using a fabricated nanocomposite, ZnO/SiO₂/GO

The objectives of this work were to fabricate the nanocomposite zinc oxide/silicon dioxide/graphene oxide (ZnO/SiO₂/GO) by decorating ZnO nanoparticles (NPs) and SiO₂ NPs onto graphene oxide (GO), aiming for efficient enhancement of the photosynthetic capacity of quinoa grown under high NaCl conditions. The nanocomposite was characterized by an absorption peak at 354 nm, spherical particles averaging 44.57 nm in diameter, and a surface charge of +34.28 ± 4.1 mV. Seeds were soaked in the nanocomposite and germinated in pots treated with NaCl at concentrations of 200 mM, 400 mM, and 500 mM. High salinity significantly reduced photosynthetic pigments, gas exchange parameters [net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), and water use efficiency (WUE)], chlorophyll fluorescence parameters [minimum fluorescence (F₀), maximum fluorescence (Fm), variable fluorescence (Fv), maximum efficiency of PSII (Fv/Fm), maximum fluorescence yield (Fm'), photochemical efficiency of PSII in the light (Fv’/Fm’), PSII efficiency (ΦPSII), and electron transport rate (ETR)], and activities of photosynthetic enzymes [ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), triose phosphate isomerase (TPI), fructose 1,6-bisphosphate aldolase (FBPA), sedoheptulose 1,7-bisphosphatase (SBPase), and phosphoribulokinase (PRK)]. Conversely, intercellular CO₂ concentration (Ci), nonphotochemical quenching (NPQ), and photochemical quenching (qP) increased under salinity. Application of the fabricated nanocomposite effectively mitigated the NaCl-induced deterioration of all tested parameters, restoring them close to control levels. These findings demonstrate that although high NaCl levels impair photosynthetic parameters, the nanocomposite supports photosynthesis, indicating its safe and effective use in enhancing quinoa’s photosynthetic capacity under high salinity and improving the performance of the photosynthetic apparatus.