Foliar Application of Choline Chloride and Ferulic Acid Regulated Osmolyte Accumulation, Nutrient Acquisition and ROS Metabolism to Lessen Chromium Effects on Barley (Hordeum vulgare)

Chromium (Cr) toxicity negatively impacts plant growth, which can lead to decreased agricultural productivity and food security. This study investigated the potential effect of choline chloride (CC) and ferulic acid (FA) in mitigating the toxic effects of Cr on barley plants. The aim was to enhance growth, improve metabolite accumulation, strengthen antioxidant defense, reduce oxidative damage, enhance nutrient status, and minimize Cr uptake in two barley (Hordeum vulgare L.) varieties, Talbina-21 and Jau-17. A concentration of 150 μM of Cr significantly decreased growth parameters. However, foliar applications of CC (5 mM), FA (0.5 mM) and or a combination of both (CC+FA) improved growth traits, with the most significant benefits observed in Talbina-21. The experimental design was a completely randomized design with three replications of each treatment arranged in a factorial manner. Cr stress led to a reduction in chlorophyll content and relative water content, but CC, FA, and CC+FA treatments effectively enhanced these parameters, particularly in Talbina-21. The treatments also increased the accumulation of secondary metabolites, osmolytes, and antioxidants, such as phenolics, flavonoids, proline, glycine betaine, and ascorbic acid. Furthermore, CC and FA spray enhanced the activity of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), which helped in scavenging reactive oxygen species (ROS) and preventing oxidative damage. The combination of CC and FA exhibited a more pronounced effect on the mitigation of Cr damage compared to CC and FA alone. Additionally, CC, FA, and CC+FA treatments substantially reduced Cr accumulation in the roots, stems, and leaves, with CC+FA showing the greatest reduction. Overall, the CC+FA treatment was the most effective in alleviating Cr-induced stress, promoting barley growth, enhancing antioxidant defense and minimizing Cr accumulation in plant tissues. This cost-effective and sustainable approach offers a promising strategy to improve crop productivity and ensure food safety in Cr-contaminated soils