Exogenously Applied Cyclitols and Biosynthesized Silver Nanoparticles Affect the Soluble Carbohydrate Profiles of Wheat (Triticum aestivum L.) Seedling

Cyclitols, such as myo-inositol and its isomers and methyl derivatives (i.e., d-chiro-inositol and d-pinitol (3-O-methyl-chiro-inositol)), are classified as osmolytes and osmoprotectants and are significantly involved in plant responses to abiotic stresses, such as drought, salinity and cold. Moreover, d-pinitol demonstrates a synergistic effect with glutathione (GSH), increasing its antioxidant properties. However, the role of cyclitols in plant protection against stresses caused by metal nanoparticles is not yet known. Therefore, the present study examined the effects of myo-inositol, d-chiro-inositol and d-pinitol on wheat germination, seedling growth and changes in the profile of soluble carbohydrates in response to biologically synthesized silver nanoparticles ((Bio)Ag NPs). It was found that cyclitols were absorbed by germinating grains and transported within the growing seedlings but this process was disrupted by (Bio)Ag NPs. Cyclitols applied alone induced sucrose and 1-kestose accumulation in seedlings slightly, while (Bio)Ag NP doubled the concentrations of both sugars. This coincided with a decrease in monosaccharides; i.e., fructose and glucose. Cyclitols and (Bio)Ag NPs present in the endosperm resulted in reductions in monosaccharides, maltose and maltotriose, with no effect on sucrose and 1-kestose. Similar changes occurred in seedlings developing from primed grains. Cyclitols that accumulated in grain and seedlings during grain priming with d-pinitol and glutathione did not prevent the phytotoxic effects of (Bio)Ag NPs.