A nanotechnology-based approach to enhance caraway (Carum carvi L.) productivity, chemical, biochemical and essential oil under salinity stress

Abstract

Salt stress is an abiotic stressor that adversely affects the growth and productivity of caraway, an important aromatic plant. A randomized complete split-plot design was used to determine the nanoparticles of zinc oxide (ZnO NPs) effects at levels of 0, 0.2, and 0.4 g L -1 on fruit yield, chemical and biochemical composition, and essential oil (EO) productivity of caraway plants subjected to saline irrigation water containing 0, 1, 2, 3, and 4 g L -1 sodium chloride (NaCl). The results indicated that increasing NaCl concentrations significantly reduced yield traits, relative water content, salinity tolerance index, leaf pigment concentrations, N, P, K, and Zn concentrations, fruits’ total proteins and total carbohydrates and percentage and yield/plant of essential oil (EO) in comparison to the untreated plants. Conversely, proline content, Na% and Cl%, and the activities of catalase, peroxidase, superoxide dismutase, and polyphenol oxidase increased with increasing NaCl concentrations relative to the control. Foliar application of ZnO NPs significantly increased the parameters relative to the untreated control except proline content, Na%, and Cl%, which were in comparison to respective control significantly reduced. Moreover, utilization of ZnO NPs positively affected the traits mentioned above under all NaCl concentrations tested compared to treatments without ZnO NPs. Different combinations of NaCl and ZnO NPs concentrations had varying effects on EO composition. A total of 32 compounds were identified across all treatment combinations, with the highest number (14) observed in the control. The major EO compounds were carvone (up to 49.71%) in the 2 g L -1 NaCl + 0.2 g L -1 ZnO NPs treatment, limonene (up to 28.68%) in the 2 g L -1 NaCl + 0.4 g L -1 ZnO NPs treatment, and D-limonene (up to 25.95%) in the 4 g L -1 NaCl + 0 g L -1 ZnO NPs treatment. These results suggest that the application of ZnO NPs may provide a sustainable approach to caraway cultivation under saline conditions.