Metabolic profiles and some physiological traits of three rice cultivars differing in salinity tolerance under salinity stress at the germination stage

This study aimed to investigate salinity's impact on the germination process and the metabolic profile of germinated seedlings in three rice cultivars known for their varying levels of salinity tolerance. The seeds of three rice cultivars, KDML105 (saltsensitive), IR29 (salt-sensitive), and Pokkali (salt-tolerant), were germinated in two different treatments: distilled water and a 40 mM NaCl solution. Salinity delayed seed germination and caused root shape abnormalities. The root length of all cultivars was significantly decreased by salinity; however, Pokkali showed the highest root length among these cultivars. Salinity also decreased total soluble sugar, glucose, and fructose content, while starch content was unaffected. Na+/K+ ratio in root and shoot was significantly increased in all cultivars; however, the increase was much lower in the tolerance cultivar. Metabolic profiles revealed several biomarkers of the salt stress response among cultivars and between the control and stressed groups. Gammaaminobutyric acid was increased in all cultivars. Citric acid, L-lysine, and L-valine were reduced, while uracil was increased in KDML105. L-lysine, succinic acid, and L-methionine were decreased, while adenine was increased in IR29. Oxalacetic acid, L-proline, and urea increased while melatonin decreased in Pokkali.