Enhancing antioxidant enzyme activities in chrysanthemum plantlets (Chrysanthemum morifolium Ramat cv. 'Jimba') under salt stress: A response surface methodology approach evaluating NaCl and CeO2 nanoparticles interactions

Abstract

The chrysanthemum (Chrysanthemum morifolium Ramat cv. “Jimba”) is one of the cut flowers with high economic value, but due to the impact of climate change, it is easily affected by various abiotic stresses, especially salinity. Therefore, it is important to enhance the adaptability, growth and development of plantlets under saline conditions. Cerium oxide nanoparticles (CeO2NPs) are usually known as stimulants in agriculture that enhance the tolerance of plants to abiotic stresses, including salinity, by promoting the activity of defense enzymes. In this study, the effects of CeO2NPs on relative growth rate (RGR), reactive oxygen species (ROS) generation, enzymatic antioxidants activity, growth and physiological parameters under salt conditions were examined. As expected, salinity reduced the RGR, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) enzyme activity, as well as morphological and physiological parameters, but enhanced O2− and H2O2 generation. However, the combination of 30 mM NaCl and 12.8 mM CeO2NPs, which were maximal salt-tolerant threshold of the plantlet and corresponding CeO2NPs concentration determined based on the response surface methodology (RSM), significantly enhanced the antioxidant enzymes activity in removing O2− and H2O2, and increased morphological characteristics (such as plant height, root number and root length) and physiological parameters (including total chlorophyll and chlorophyll a/b ratio), leading to better growth and development of plantlets. Exceeding the above salinity threshold, adding more CeO2NPs did not result in good growth similar to plantlets derived from medium without salinity. This study provides new insights into the determination of interactive effect between CeO2NPs and salinity on the growth of chrysanthemum, thereby improving the yield of this species. CeO2NPs enhanced chrysanthemum plantlet growth under salinity by increasing antioxidant enzyme activity. Response surface methodology was streamlined and improved the accuracy of determining salinity-material correlations.