Enhancement of drought stress tolerance in okra (Abelmoschus esculentus L. Moench) through the application of carbon nanoparticles.

This study aims to investigate the impact of carbon nanoparticles (CNPs) on seed germination, seedling growth, nutrient uptake, and the physio-biochemical characteristics of seedlings under water-limited conditions, along with the regulation of gene expression. Okra seeds were treated with CNPs at concentrations of 0, 25 mg/L, 50 mg/L, 100 mg/L, and 200 mg/L, with germination tests conducted using drought conditions simulated through PEG-6000 solutions. A pot experiment was designed to assess plant growth, nutrient uptake, physio-biochemical properties, and transcriptomic changes. Four specific CNP concentrations (0 mg/kg, 50 mg/kg, 100 mg/kg, and 200 mg/kg) and three watering intervals (every 3 days, 6 days, and 8 days) were employed. The results demonstrate that CNPs application significantly enhanced the germination characteristics of okra seeds under water deficit stress, leading to improved root development, nutrient (N/P/K) uptake, and various photosynthetic traits, including chlorophyll content, photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate. Additionally, the activity of superoxide dismutase (SOD) and catalase (CAT), along with the accumulation of glycine betaine, total phenols, total flavonoids, and total soluble sugar, were notably higher in CNP-treated seedlings compared to those without CNPs across different water-limited scenarios. Transcriptomic analysis revealed differential expression of genes, particularly those related to starch and sucrose metabolism. These findings underscore the beneficial role of CNPs in enhancing seed germination and seedling growth of okra under drought stress, while also providing valuable insights into the optimal application levels of CNPs to boost agricultural productivity.