Ethanol-mediated Cold Stress Tolerance in Sorghum Seedlings Through Photosynthetic Adaptation, Antioxidant Defense, and Osmoprotectant Enhancement

Sorghum (Sorghum bicolor L.), an often overlooked but vital staple crop, suffers severe obstacles in growth and yield due to temperature fluctuations, especially low temperatures. Therefore, scientists nowadays pay impulsive attention to overcoming the deleterious consequences of cold stress (CS) in sorghum. Our current investigations revealed that the application of ethanol (0.2 %) to the root zone of sorghum plants enhanced biomass production, improved gas-exchange features and the levels of photosynthetic pigments, and enhanced leaf relative water content, which collectively contributed to a significant enhancement in the growth performance of sorghum seedlings when subjected to CS conditions (8 °C). Exposure to CS leads to a substantial buildup of reactive oxygen species (ROS), notably hydrogen peroxide, along with elevated levels of malondialdehyde and electrolyte leakage in sorghum leaves, unequivocally indicating the occurrence of oxidative stress in sorghum seedlings. In contrast, the addition of 0.2 % ethanol demonstrated a remarkable ability to alleviate the oxidative burden caused by ROS by substantially enhancing the activities of key antioxidant enzymes, including catalase, peroxidase, glutathione S-transferase and ascorbate peroxidase, and the level of total flavonoids, within the leaves of sorghum seedlings subjected to CS. Furthermore, ethanol treatment exhibited additional benefits by increasing the levels of total soluble sugars and total free amino acids in sorghum seedlings, which are likely to play a pivotal role in maintaining osmotic balance in response to CS. In conclusion, our findings highlight the defensive mechanism modulated by ethanol in promoting the adaptation mechanisms of sorghum seedlings for abatement of cold-induced damage.