Effect of nanoparticles on sugar beet cultured in vitro and its betalain and betaine production

Sugar beet (Beta vulgaris L.) is considered one of the most important crops in terms of economics and food. With the widespread applications of nanoparticles (NPs) in plant science that have received great interest due to their amazing results and promising capabilities, the aim of this research was to investigate the effect of TiO2 and ZnO NPs on sugar beet plants cultured in vitro in several respects: seed germination, morphology, chlorophyll a and b contents, carotenoids, and the most important sugar beet metabolites, betaine and betalains. To investigate the effects, four different concentrations of NPs (0, 5, 15, and 25 mg/mL) were applied to two genotypes of sugar beet. Following the applications, germination numbers and root and hypocotyl lengths were measured. Further, chlorophyll, carotenoids, betaine, and betalains contents were estimated and compared. Plants exposed to NPs did not show a significant difference in seed germination, chlorophyll contents, or carotenoids as compared to the controls. On the other hand, betaine showed improvement at low concentrations of NPs and gradually decreased with increasing concentrations in both genotypes. Concerning betaxanthin, the monogerm genotype (SG833) showed a statistically significant increase in plants exposed to TiO2 NPs with concentrations of 15 and 25 mg/mL, while in the multigerm genotype (SG2020), a significant improvement was shown in plants exposed to ZnO NPs at concentrations of 15 and 25 mg/mL. Regarding betacyanin, it showed a statistically significant enhancement only in plants exposed to 25 mg/ mL ZnO NPs in the monogerm genotype. The effects of ZnO and TiO2 NPs at varying concentrations on sugar beet were studied. The research focused on the production of betaine and betalains, which are important secondary metabolites. The results indicated the possibility of increasing the production of these compounds while avoiding any negative or phytotoxic effects.