Effect of salicylic acid on germination and seedling growth of KhaoRai Leum Pua Petchabun (Oryza sativa L.) under combined drought stress

This study investigates the influence of salicylic acid (SA) on the germination and seedling growth of KhaoRai Leum Pua Petchabun rice (Oryza sativa L.) under combined drought stress conditions. We evaluated various SA concentrations (0, 0.25, 1, 2, 4, 8, and 16 mM) on rice seeds and seedlings in a controlled environment, employing polyethylene glycol-induced drought stress as a model for stress interaction. Parameters such as vigor index, fresh and dry weight, shoot and root length, relative water content (RWC), pigment content (chlorophyll A, chlorophyll B, and carotenoids), and reactive oxygen species (ROS) production were measured. The data reveal that SA application significantly ameliorated both germination and seedling growth under combined drought stress. Specifically, SA treatment favorably impacted vigor index I and II, fresh and dry weight, and RWC, with 1 mM and 2 mM SA concentrations showing the most substantial improvements. Shoot and root lengths were also augmented by SA treatment, peaking at a 2 mM SA concentration. Pigment content analysis indicated an elevation in chlorophyll A, chlorophyll B, and carotenoid content in SA-treated plants, particularly at lower concentrations (0.25-1 mM), suggesting enhanced photosynthetic efficiency. Moreover, plants exposed to higher SA concentrations (8 and 16 mM) displayed significantly diminished ROS production, indicating a mitigation of oxidative stress under combined drought stress conditions. In conclusion, SA treatment effectively enhanced the germination and seedling growth of KhaoRai Leum Pua Petchabun rice under combined drought stress by improving water retention, augmenting photosynthetic efficiency, and alleviating oxidative stress. These findings propose that SA application may serve as a viable strategy for boosting rice production in drought-prone and stress-interactive environments.